Hunting for noise

[Nick]

My plans to hunt down the noise problem in my system got off to a false start with the purchase of an Oscilloscope that turned out to be no better than a toy.

( more here  http://www.phasure.com/index.php?topic=2404.msg27276#msg27276)

Six months later I'm getting started. A new oscilloscope, a Rigol DS2072, arrived a couple of days ago. I have to say the Rigol is an absolutely excellent bit of kit. I also bought a PC attached USB logic analyser a few weeks ago with 8 digital inputs and 2 analogue traces. The cool thing is that the logic analyser decodes the I2S serial protocol which allows me to view the bit clock, word clock and data values being sent into the DAC section of my NOS1, The bits and bytes look good too after Peter has applied XX magic to them  So tools at the ready !

I spent a few hours today measuring round my NOS1, PC and gainclones with the Rigol scope to get a feel for what may be going off that could cause poor sound quality. Some VERY surprising stuff is coming to light. I want to spend more time working up solutions but a couple of things that are interesting so far.

1) there is a LOT of noise in there.
2) I can clearly see activity from the PC (disk drive and PC psu) causing noise on the NOS1 outputs (so the PC does have potential to electrically influence analogue outputs ??)
3) after applying a few ferrites to the system aimed at reducing HF noise my sound quality has taken a leap forwards. The ferrites are treating the symptoms only, dealing with the source of the noise I'm seeing may be a lot harder.
4) I use a "none standard" 22mhz oscillator (clock) in my NOS1. The sound is very good with the clock but the wave form of the clock looks like it could be better. I think I'll need to investigate how to achieve better line matching with the clock input of the USB interface.

It's nice to be making some headway and to be using a scope that can be trusted !

Regards,

Nick.

[PeterSt]

Now Nick, don't tell me that you didn't try to play music with the DAC section off as a first ?!

(this will be vague to all, sorry)

Peter

[Jud]

Nick, great to see someone being serious enough to buy equipment I'd love to have, but for now isn't in the budget.  Will be happily following along, reading about your "discoveries."

[Nick]

Now Nick, don't tell me that you didn't try to play music with the DAC section off as a first ?!

(this will be vague to all, sorry)

Peter

Peter hi,

I have not tried that yet although the balanced gainclones are a better in that respect so I am not sure they would perform 

I think I may know what is allowing the break through at -144db volume 16x up sample and the poor SQ to happen. How many times have I said that, haha. The plan is to try to repeat the measurements and check the effect of the ferrites again. If it checks out as before I will drop you a pm, I may need some help 

Regards Nick

[Nick]

First finding - How to encode an audio signal in an I2S data stream.

A quick recap

I have been having a problem with my audio system for a year and a half. There are two main symptoms:

1)   General loss of resolution increase in harshness collapsing of sound stage and dynamics when playing at high (16x) up-sampling rates (linked to when 2) is present) and,

2)   When Playing music at a -144db XX volume setting, I can hear a distorted version of the music playing at low levels through my speakers. What is surprising is that the DAC converters and IV section of my DAC can be turned off and yet still this breakthrough music can be heard.

Trying to approach this my thinking was that symptom 1) is quite general and none specific, it could be almost anything causing it so its difficult to test even with my new test equipment on hand.
Point 2 however is quite interesting. Key here is the diagnostic assumption that if I could hear the music breakthrough even with the DAC turned off then something in the digital domain upstream was decode data to an audio frequency music signal. But how was this happening ?

Main suspects were:

1)   Some unintended DAC process in the PC (there are DACs in the PC but there shouldn’t be working …). I decided this was un-likely following a few tests and discussions with Peter.

2)   I have worked on USB to SPDIF interfaces with build in DACs in the past. Might it be that the NOS USB interface has a DAC on board and this is unintended decoding the music data. Peter kindly confirmed that there is no such feature on the NOS1 USB interface, so this was ruled out.

3)   Is the USB stream from PC to DAC somehow modulated by the music signal ? Could possibly be the case but not sure how. If necessary I could can test with my logic analyser

4)   Is the I2S data stream that links the NOS1 USB interface card to the DAC might somehow be modulated by the music signal ? This stream of data is very close electrically to the output of the DAC, there are many reports of I2S being noisy on the net, and there is the possibility of timing problems with I2S signalling so this is where I decided  to start looking.

Peter has been very helpful and we have been sharing ideas and experiences relating to I2S observations over the last weeks. Amongst points Peter raised was that the 1704 DAC chip uses 2’s complement binary data encoding to pass music data over the I2S data stream into the DAC.

When looked into the key here is that bit values and therefore the electrical “on” and “off” values of the I2S data near the zero vale of the musical wave form look very different when they are passed down the I2S data connection.

For example:

0 (dec) = 0000 0000 0000 0000 0000 0000 (24bit Binary) so electrically for this music value the I2S data line is “off” at 0 volts to send a 0 value. Likewise positive low values are mostly zeros (offs).

-1 (dec) = 1111 1111 1111 1111 1111 1111 (24bit Binary) so electrically the I2S line is “on” at 3.2 volts to send a -1 value.  Other negative music data values just below 0 are also mostly 1s (ons).

A couple more useful bits of information that turned out to be relevant:

• I2S data is sent at the logic gate values of the sending and receiving chips so in the case of my interface that’s 0v = an off bit and +3.2volts = an on bit.
• I estimated the peak to peak voltage amplitude that would be needed at my DAC’s output XLRs to generate the breakthrough music sound level I hear played whilst at the XX volume setting of -144db to be in the rage 100uv to 500uv. (from an estimate that the volume heard is about 50db at 1m, played via 103db/w/m loudspeakers and a 36db amp).
  

So the I2S carrier of 0-3 volts square wave signals at a carrier frequency (data bit rate) of up to 22mhz per I2S line  and there are two I2S data lines in use within the NOS1. Is seemed possible that the breakthough audio signal of 100-500uv could be coupled to the output of the DAC even with the DAC chips turned off. Now time to look for how an audio frequency signal could be encoded into the electrical conditions of the I2S data lines.

I obtained an 8 channel logic analyser (which decodes I2S data) and a 200Mhz oscilloscope to probe the I2S data lines with music playing at -144db. I was amazed to see the following emerge.

Traces taken with logic analyser.

Key of the trace lines in each picture.

• Top trace line is one of the two I2S lines in the NOS1 with the software set to decode the music word values being passed to decimal values. Note that that since this is tws compliment data that the music value of -1 is decoded to Dec 1677215 (bin 11111111 11111111 11111111).
• The next trace line down is the raw I2S data on the NOS interface so low is 0 volts and high on this trace a 3.2v condition.
• The next line down is the word select clock which changes state every 32 bits word sent on the I2S data lines.
• And the final  line down is the bit clock signal.

First trace
1 khz test tone recorded at 0db played with XX volume at -144db not upsampled (44.1khz).

This is a close up of what happens when the music wave form values (in this case a sine wave attenuated by -144db) moves from a positive in the wave cycle to a negative part of the wave cycle. Note that when the music wave was above the zero point the wave is attenuated to the binary value of 0, so the electrical state of the I2S line is mostly 0v. However when the sine wave was in the negative cycle the attenuated value never gets to 0 it stays as -1 and due to the two compliment treatment of the I2S data the electrical value of this -1 data is a state of mostly +3.2volts.

I was looking in my system for a misbehaving semiconductor acting like a diode to demodulate the data transmission, but the actual I2S line and Twos Complement state values themselves are creating an electrical state on the I2S data line that corresponds to zero crossing points in the music wave form ! oh boy 

So now lets look at zoomed views of the trace so that you can see a longer duration of the sine wave with more transitions of the music sine tone across the zero value point.

Humm, the electrical condition of the I2S data line is now a good approximation to a square wave at the 1khz frequency of the music sine wave. The square wave has a low value of 0v when the original audio sine wave signal was of a value below zero and a high value of 3.2 volts when the audio value was below zero.

Bloody hell QED  ! the audio signal IS being demodulated into the I2S data transmission voltages.

From here it is a short step. The modulated data (I have looked at many many more measurements including normal music and its facinating watching the demodulation take place, the audio looks like Pulse Code Modulation centred on the zero crossing point as the volume us raised from -144db upwards) is being carried at up to the bit clock frequency on a square wave of approaching 22mhz. This frequency of carrier and its overtones can couple with near by traces / connections power rails etc. I need just 100uv to couple to the DAC outputs and that plays the breakthrough sound – which is what is happening.

Continued in next post

[Nick]

Continued 2 of 2


So a few throughs on this process.   

All DACs that use I2S inputs and twos compliment encoding for input data will encode audio in their I2S data line electrical transmission (some DACs use straight binary encoding and will not suffer). This is not a special condition of the NOS1 although the high data rates used by the NOS seem to complicate matters here in my system. The problem is at its most noticeable when the I2S transmission rate is high (eg when up sampling at 16x) and both 12S lines are active together. Playing at -144db highlights the modulation to the maximum degree but it is always happening as music plays. What I can say is that the amount of breakthrough at -144db that I hear is strongly linked to how good that quality of normal music replay will be in my system. So far I do not understand the coupling of the I2S line to the outputs of the DAC but this is what I have to work on next.

Finally, I must thank Peter who has spend a lot of time exchanging mails with ideas and information about the NOS and the encoding of the I2S lines. We had a very interesting conversation earlier this week using webex to share a number of analyser traces and the conversations are really helping me to plan next steps which will be about controlling PC and DAC noise levels.

Nick.

[PeterSt]

Hey Nick,

Yes, what a travel this has been. But allow me to make a tiny correction because I am too proud on myself ...

Peter has been very helpful and we have been sharing ideas and experiences relating to I2S observations over the last weeks. Amongst points Peter raised was that the 1704 DAC chip uses 2’s complement binary data encoding to pass music data over the I2S data stream into the DAC.

So ... I am really too proud on myself to skip the small part that at that stage I finally could tell what was going on, and how without a DAC music can be heard from i2s itself.
So, with your analyser under way, and for me too after 1.5 years or so throughput time and countless emails about this totally not understandable phenomenon, I could tell that the zero crossing you so beautifully explained for next readers, happens like this :

Zero crossing (voltage goes from minus to plus and back) happens at the lowest frequency only;
This implies a voltage jump - the highest possible - because it's going from all zeroes to all ones in the DAC.
It was my assumption that even with the DAC off, this could leak through because of the relatively high current needed to do this.

At this stage I needed to measure the output of the DAC with the DAC section off, while your analyser was under way.

Do notice the importance of Nick's telling that the lower the digital attanuation, the more the music was audible.
Nice puzzle.

Now, with the help of the logic analyser, we can see that this current needed (the voltage jumps) already happen in front of the DAC, with at this moment the jury still being out to the leakage through the outputs. But :

What I by then (this week) could reason out is that the lower the level of the music (like -144dB is ultra low) the lower the level of the wave of that low frequency, and the LONGER the time period the higher frequencies riding on that lowest frequency (which is how it works) are able to cross zero themselves. This is how the more attenuation, the better the representation of the music becomes, because the more higher frequencies imply the zero crossing.
Compare this with 0 attenuation, the frequency (time distance of the lowest frequency wave) not changing, while the zero crossing is close to vertical and there's no time for higher frequencies to go back to plus once the low frequency crossed zero to minus.

Next, but actually right before the "analysis" from the last paragraph, it was totally 100% Nick who could explain by means of the graphs shown in his previous posts, that this is a pure i2s thing, while I anticipated an in-DAC chip thing. So, the "pulse width modulation" I named it by looking at the i2s behaviour (I think Nick named it somewhat differently) has a life of its own, and Nick pointed that out so SUPERBLY.

At writing this I feel like a couple of guys won a Nobel prize. Really.
It wouldn't be the invention of the century perhaps, but I am pretty sure nobody ever saw this.
What a victory.

For me this definitely means how further improvements on a DAC are possible and right away it is in some design already.

For Nick it is the path to eliminate this noise leaking through, which really should not happen. It doesn't happen to me, at least not audibly even the slightest, but what can happen with Nick can happen to anyone, thinking about external factors.

Great stuff !
Peter


PS: I edited out one aspect from your post which was irrelevant (and therewidth wrong), which correction I hope you will grant me.

[PeterSt]

And Nick, might you still have that picture, IIRC the -108dBFS attenuation shows the Pulse Width Modulation at the bit level (or otherwise it was the -124dBFS file). I think what you showed in your post shows something at the audio word level, which does not justify the PWM idea.

One other thing to add from my side :
The zero crossing at -144dBFS (which is what Nick showed) should not be there at all, but is. I dedicate this to something wrong in the USB driver, knowing that XXHighEnd really throws out zeroes only at that level of attenuation. I longer ago saw this in my own analyser too.
This is not important for the whole story but should be solved. Just saying ...

Peter

[Nick]

Peter hi,

Sorry it absolutely not my intension to understate the amount of help and support you have provided. All of the guidance you have given to help me with the noise problems (proberbly 100s of emails :-) ) and the conversations we have had leading up to capturing this view of the I2S data. I decided to look at the I2S bus but without this guidance and your generosity with information and insights these views of I2S would not exist. You know that there is much that you have said to me that is not for discussion  that would immediately demonstrate the depth of your understanding of what happens across the end to end DAC system 

I also agree it is unlikely that others have not seen this demodulation of audio data in action, and I also feel like we reached a goal together in understanding this small element of a DAC operation. I think this will prove useful.

And Nick, might you still have that picture, IIRC the -108dBFS attenuation shows the Pulse Width Modulation at the bit level (or otherwise it was the -124dBFS file). I think what you showed in your post shows something at the audio word level, which does not justify the PWM idea.

One other thing to add from my side :
The zero crossing at -144dBFS (which is what Nick showed) should not be there at all, but is. I dedicate this to something wrong in the USB driver, knowing that XXHighEnd really throws out zeroes only at that level of attenuation. I longer ago saw this in my own analyser too.
This is not important for the whole story but should be solved. Just saying ...

Peter

Interesting about the USB driver convering zeros to ones. The logic analyser can decode USB data so I could try to take a look at what is passed on the d+ d- lines.

Here are the traces that show the PWM effect of the positive binary count and negative binary count (in twos compliment) on each side of the test tone zero point. The zoomed really show the effect nicely.

For folks  looking at the traces, concentrate on the PWM appearance of the brown coloured trace labelled “IS2 2”.


Trace details
Sine Test Tone 1khz 0db
Played in XX at -108db vol
DAC 24bit 88.2khz

Best Nick.

[PeterSt]

Sorry it absolutely not my intension to understate the amount of help and support you have provided.

Hahaha, as I could expect, nothing could prevent you from now thinking something like that. But no, this was not my "message" at all. I didn't have any message. But what I wanted to make clear is that it is of such vast importance for me that I could finally reason out that such a phenomenon - and without measuring - could make music. This after all the so many emails with reasoning I could not. And so I dedicated 50% of the "Victory" to myself, because I always like to apply (new) theories and after that let them work (no matter what).

Like your first post about it, for me too is was a "Finally ?!". Could be hard to understand for outsiders, but after 1.5 years of (regularly) thinkering about how the heck music could emerge without D/A converter it really is something which was achieved. For history, here's a part of our 100s of emails throughout the process; this is what I wrote last July 10, and btw I can see from the text that you had the logic analyser by then :

Cautious conclusion : there really can be something in your "breakthrough" from the one to the other i2s channel. But it needs real data, and don't ask me how you can judge that through your digital probes. Hopefully you can (and hopefully you have that real i2s package of which I said you wouldn't need that ? hahaha).

Still my analyser keeps on showing the test signal (of each frequency) no matter how much I attenuate (FYI : stays as high from off -108dB all the way to -144dB).
I can not see that on the scope part, but the FFT digs it out.
I never tried measuring this with my DAC section off, but by now I dare to bet a few things ...


When some interestee, later, passes along this topic, I expect those with the knowledge to say "well, so what, this is just i2s data we see here". And this is correct of course, and nothing different from my sort of reluctancy to not needing an i2s decoding package as we see (implied) quoted in the first paragraph above. So, while my theory was hung up to glitching in-DAC (which would be a sheer R2R process in our NOS1 case), it was still you coming up with the data after which we could see that this glicthing is actually an inherent i2s process. And THAT is new.

So to work this out somewhat more from the technical side of things - if not already done by yourself in the first post - ... when an R2R chip crosses zero and say a +0V for zero turns into a -2V for -0.0001 (just one smallest value lower than 0) there's a large current implied and this is named a "glitch". This expresses as an AC voltage (read : music) spike of a couple of 10 uV, depending on the D/A chip (btw the PCM1704 says it isn't there, which would be true because I can't see it because of the relative high level of noise).
With i2s though, this is 3.3V going to 0V and the other way around, thus even more than in-D/A chip.

So again from the quote above - now second paragraph - I already had worked out that something has to be going on, because I had seen that beyond the resolution the D/A chip can resolve (because all drops into the noise) I could see a very persistent normally looking test signal of any frequency remain, no matter how much the attenuation. This by itself is a story in parallel and about seeking a bug in some design which bug could not be found and I gave up and layed it aside.
Now, today, it is totally clear to me that whatever the frequency of the test signal, and no matter how low level it is, there is this glitch in i2s which happens at zero crossing and which of course is 100% equal to the frequency itself.

Because this frequency keeps on sticking above the field at a standard level (something like -120dB IIRC) it is just the glitching energy of i2s I see (at a noise level of -143dB). So, this is about the few tens of uV I talked about, and it will never go away. With real music the same will happen, and each zero crossing, which can be for the higher frequencies which modulate on the lower) this will be just the same, and if only the level of the music is low enough, this other source of "music" will become profound, but is distorted. It is distorted because only when zero is crossed it can briefly do its work for the higher frequencies, while for the lowest it will be rather pure with the notice the level of it can't change (because it's always implied by the 0V-3.3V current needed).

So, learned another thing ...
What's next ?

Peter
 

[pedal]

Wow, hats of to you guys.
I will read the full thread later, but it seems you have made a world discovery!

The i2S is the internal interface/signal format within all integrated CD players, right?

Does this mean that ALL CD-players suffer from this kind of distortion?

[Nick]

Wow, hats of to you guys.
I will read the full thread later, but it seems you have made a world discovery!

The i2S is the internal interface/signal format within all integrated CD players, right?

Does this mean that ALL CD-players suffer from this kind of distortion?

Pedal hi,

Yes I2S is a the line standard for sending digitally encoded music. In out case it sends the data to the DAC board of the NOS. The is a data line with in our case twos compliment encoded data being sent. A word select line which triggers 32bit music data chunkes to be sent to left and then right channels and last of all a bit clock which "times" each bit of the 32bit data words.

The NOS is rather more clever than a "normal" DAC in how the data is handeled but essentially I2S is what moves the data towards the DAC chips.

All CD players the use I2S to move data coded in twos compliment binary form will experience the decoding of the audo signal into the electrical conditions of the I2S data line. Depending on a number of factors this may or may not effect the DAC performance (a low res slow speed dac with poor noise floor will probably not suffer  but that is not the NOS).

Some DACs use straight binary encoding rather than twos compliment and will not suffer BUT even these may encode music onto the I2S line, but rather than this happening when the music crosses the zero point as with I2S the straight binary the encoding will happen as music waves get towards minimum (more zero bits sent)  and maximum (more 1 bits sent) music values. This is likely to be much better however as the signal level is in the region of 0db so the encoded noise should be drowned anyway.

When Peter is sweating the last grams of performance for us this is very important stuff.

Cheers Nick.

[Nick]

Peter hi,

>>What's next ?

With the aim of eliminating noise here I was thinking.

Probe the I2S into the 1704s and check data against where I am currently sampling. Also check analogue I2S conditions into the 1704s this gives the full picture dome the the converters just to be complete.

Check the D+ D- analogue conditions of the USB link to see how they look and maybe decode the data but not sure of I'd work out the frame structure (proberaly not that important to do).

Build a field probe to go looking for devices / lines that are emitting the I2S encoded data and where coupling to unwanted areas may be happening.

See the last post to Pedal above on binary encoding I think it may also encode the elecrical I2S line in phase with the music wave form but much better behaviour at wave values in the region of zero than with twos compliment.

-----------

On another subject, Paul and his wife were with us for a very enjoyable day today. Whilst tinkering with my music system we put Paul's PC on the front end of my NOS and SQ was so absolutely brilliant !  I could stop hear with the noise quest it was so good, it was mouth open time for both of us :-). The -144db noise is there as expected and music still sounded better at 8x up sampling still (hence the intent to look at data reaching the 1704s just in case).

I suspect I have a duff PC somehow ! So something else concrete to look into. Right now Paul and I were thinking I should build a PaulClone PC, there is something magical in the sound of Paul's machine both at his house and at mine.

Cheers,

Nick

[Scroobius]

Just a note to say that I do not have any noise breakthrough problem here at my house. Well by that I mean that if I play music at -144db there is no breakthrough at all that I can hear in my system at my home. It does not mean that the IIC problem is not happening here though - I would need Nick's scope to check further and that is something we may do when Nick's comes here in a few weeks time.

However yesterday we tried my PC at Nick's house and the breakthrough problem happens with my PC. It also happens with my NOS1 and (not surprising) with my old single ended GC amp which we have tried on a previous visit.

So what is happening at Nicks house that is not happening at mine?

Very weird indeed.!!!

Paul

[boleary]

Hey Nick didn't you post some time ago that re-enabling devices in your BIOS had a positive impact on SQ? Here that is definitely NOT the case. Disabling all Onboard Devices in the Advanced/Onboard Devices Configuration tab is essential to the incredible sounds I've been hearing.

[manisandher]

First finding - How to encode an audio signal in an I2S data stream.

Nick, most of your technical description is beyond my current level of understanding, but your findings seem totally 'crazy', 'amazing', 'revolutionary'... I'm not sure what the most appropriate term is!

Peter, do you think you can use these findings to further improve the NOS1 in general, even for those of us who are experiencing nothing like Nick is? (BTW, I get nothing whatsoever coming through at -144dB and the NOS1 switch #2 set to off.)

Mani.

[Nick]

Hi,

My Adnaco system recently returned from a holiday in Holland (thanks for looking after it Peter ).

I intended to use it only as a diagnostic tool to use whilst understanding electrical noise within the PC DAC and AMP. This was because when I first bought the system more than a year ago to try out electrical isolation of the PC from DAC, the system showed promise but ultimatly could not exceed the sound quality of the normal USB connection.

(The findings from a year ago are posted here
http://www.phasure.com/index.php?topic=2089.msg21556#msg21556)

So fast forwards to working with Anadco now. First thing is that in the intervening time frame the PC OS, XXHE software and my PC have all very significantly changed. On reconnecting the Anadco SB3 system the slightly darkened (though very pure sound and totally without "hash") sound was present again. However, in my current system the sound using the Adnaco is much better than I remembered and so I decided to spend a little time understanding the system to see if there were any settings or electrical changes that would make it perform. Well it turned out that this can be done and by a couple of relatively simple changes to the Anadco USB board. PC Bios, and XX Settings have been all over the last few days but its coming together now.

This will need other ears to verify what I am hearing and there are still a couple of points to sort out but I am really thinking that with the modification Anadco is making a significant positive contribution to sound quality.

Paul hi,  I think we have yet another configuration to test next time we meet !

Regards,

Nick.

PS Alan I think you may have bought an Anadco system at the same time I did, was yours an S3B (USB) system ?

[AlainGr]

Hi Nick,

Yes it was the S3B, but I returned it at the time, since I was not convinced that it was improving my SQ.

But if they have done something interesting towards SQ, it is quite possible that I would order it again.

So I am following you (but with discretion of course) and am always interested in your findings

Regards,

Alain

[Nick]

Alain hi,

I also almost returned my SB3 as well 

It would have been interesting if you still had the card to try the small mod on it to see if you had similar results.

The acid test for these ideas I come up with tends to be a trip to Pauls to take a listed. That soon roots out the "good" from the "wanabe" stuff. It will be interesting to see what we find with this when we get chance to get together and listen.

There are some quite exceptional qualities to the music now bit the question will be is it better "overall" as the slightly darker sound was where is fell appart last time. Now I would certainly not describe the sound as dark 

Regards,

Nick.

[AlainGr]

Ah... I read too fast and sometimes I don't see the end of a sentence, so my interpretation is totally wrong...

As for noise and or "ground" noise, do you feel that the Adnaco isolates something ?

For sure now that I have experienced the benefits of using a linear power supply, I would certainly not use the wall wart that comes with the S3B. But I wonder if noise that could run between the PC and the DAC could be at least reduced, if not eliminated. While I know that the data itself will be already polluted with this noise, I would expect the Adnaco to help me achieve more silence...

As for the USB board, are you talking about the 2 ports USB 3 reception box ?

Alain

[Nick]

Alain hi,

I think there are defiantly benefits of isolating the PC ground and noise from the PC carried by the USB signal and sheild cables etc.

I am with you regards the benefits of linear supplies but I'm am sat listening to the Anadco powered by the SMPS wall wart supply and you just would not know  . The key seems to be getting to the hart of the problem on the Anadco board and then the darkness disappears and the music just flows through with no noise from the PC. very very sweet.

Regards,

Nick.

[AlainGr]

Hi Nick,

Wow... The description that you give about the Adnaco with the modified USB board have me very interested If I was to get it again, is that modification complicated for a non DIYer like me ?

 It is the S3B isn't it ?

Regards,

Alain

[Nick]

Things are now moving on at a pace now. After having spent a fair while understanding what I think might work to deal with the noise problems, the soldering iron is well and truly out  !  

After a long time working through information that Peter kindly provided I started work on the NOS USB interface this evening. I decided to make the noise tweaks in steps so that I can assess the impact and make sure that sound quality is not negatively impacted. The first set of tweaks are now applied. I have still to check for effect on  breakthrough music being played at software volume setting of -144 db but have had a listen to the results this evening (without burn in of components).

First impressions of sound quality, honestly, OMG WTF just happened ? Its just on a different plain than before.

More work to do over the weekend and then I'll post an interim view of the results both in terms of the effect on the noise problems in my system and the effects of the tweaks to the NOS1 and Anadco on sound quality.

Nick.

[Nick]

Wow... The description that you give about the Adnaco with the modified USB board have me very interested If I was to get it again, is that modification complicated for a non DIYer like me ?

Alain

It's not difficult to tweak the SB3, but please let me do a little more work a/b ing with the standard usb setup and possibly get someone else to take a listen before you invest again. I would like to be absolutely sure the the effects are all good 

Nick

[AlainGr]

Nick,

Your advice makes plenty of sense. I will wait for the results of course.

I hope you and Paul will find the bright side of the force

Regards,

Alain

[Scroobius]

Hi Nick,

Sounds interesting. I look forward to taking a listen and if you need me to "drop in" let me know. In my recent attempts to minimise noise in my system I disconnected the USB plug into NOS1 to see if noise was reduced but I could not hear any difference. This isolated the NOS1/amp grounds (which are connected together) from the PE connection in the USB shield. Of course that only covers in band noise it does not cover out of band noise which I know is what you have been measuring.

Nick are you doing your tests with a short fibre connection? and have you done enough yet to determine if the length of the fibre has an effect on SQ?

Paul

[Nick]

Nick are you doing your tests with a short fibre connection? and have you done enough yet to determine if the length of the fibre has an effect on SQ?

Paul,

Yes I have a 2m fibre cable now and it think it does help a little. The cable though is a hygene factor compared with the tweeks to the Anadco and the USB interface.

Have sent you a mail.

Regards,

 Nick.

[Nick]

Hi,

I'v spent the best part of two days this weekend working on the NOS1 USB board with really super results. I am satisfied now with tweaks to this board so this afternoon was spent on the DAC pcb which gave up a really super tweak.  I just need to tune the DAC board tweak a little more and it's done. Did i just say its done  yes, the sound is THAT nice. I'll post on the results when I am comfortable with it all, to be honest it could be now but I know there is a little more to come.

This is all the Anadco card needs to elevate its performance. The caps are 33uf black gate n types. They are possible a little larger than needed but they were to hand and work very well.

Nick.

UPDATE 30.10.13
I have not been able to get the Anadco to equal or exceed the performance of a direct USB connection. See update posted here

http://www.phasure.com/index.php?topic=2640.msg28771#msg28771

[CoenP]

Hi,

I'v spent the best part of two days this weekend working on the NOS1 USB board with really super results. I am satisfied now with tweaks to this board so this afternoon was spent on the DAC pcb which gave up a really super tweak.  I just need to tune the DAC board tweak a little more and it's done. Did i just say its done  yes, the sound is THAT nice. I'll post on the results when I am comfortable with it all, to be honest it could be now but I know there is a little more to come.

This is all the Anadco card needs to elevate its performance. The caps are 33uf black gate n types. They are possible a little larger than needed but they were to hand and work very well.

Nick.

Hi Nick,

You are familiar with the 300 hour burn in of Black Gates? Between start and burned-in they can make a system sound like cr*p.

Just want to warn you that the results can change over time and not for the better. It is all about patience in this case like with the NOS1, in the end you will be rewarded!

Regards, Coen

[Nick]

Coen hi,

Yes i'm with you,  the cap used are recovered from other old projects where they had been run in. However they have not been used for a year or three so they will need a long bun in again. The nice thing is that hopefully the sound should improve 

Cheers,

Nick.

[AlainGr]

Hi Nick,

I am sitting on your shoulder If this experiment turns for the better, I will sure need a little course on soldering, but also exactly where to solder it

Alain

[PeterSt]

Nick,

Coen was ahead of me, but/and reading your post about the Black Gates I wanted to say the very same, but with another proposal :

First of all, to me it doesn't make much sense to put in Black Gates there. So, why do it in the first place but then with the focus on people not having them around. Thus, I'd say that any el cheapo cap will do the job here.

Then, still assumed you are looking at HF noise here, it could be a fairly moot thing to "see" that improvement was achieved. I think Coen said the same (with maybe different words), but the "pattern" will change over time (aging of the caps).

In the far end - but this is a very different story - you look at HF noise and I don't think you have any influence on it, and while possibly today for the better, tomorrow for the very worse (again the frequency changing thing).
Let's keep in mind that this is all about jitter (as far as I can see), so if you can tell me how this is going to influence jitter for the better ... I am all ears. Of course I am a bit nasty here because the answer is quite impossible to give (I think). So, I won't say there's no improvement possible here, but I do say that we won't be able to see what is for the better. And I mean : never think that less noise of high frequency is for the better. And if anything, I'd say it is for the worse, as long as noise remains (which it undoubtedly will). Higher frequency noise will imply jitter more randomly. The higher the better. Maybe it is not easy to agree upon this, but might we after all, then we also agree about this all not being so useful (up to working out for the worse).

If possible, I'd like to see the technical merits (somehow !) from the comparison between the copper connection and the glass connection. And then, sadly, with the original setup of the oscillators, which you changed quite a bit ...
Yes, sadly, because this is your concidental situation.
So whatever you come up with, at least to me it can't tell it all because it is not my situation. Nor anyone's else ... This, btw, also includes the being active of one oscillator only, which I dedicate much difference to begin with. Good stuff (for sure), but we all don't have that ...

In the far (far) end the only thing with real merit is to measure jitter (its characteristics) at the output. And here it stops I'm afraid (I am not able to do that myself).

Is your noise at -144dB completely out of the way now ? if so I say nothing. But if not, ... we don't have that either (no matter how logically it is per your own (means of) proving it).

Too many variables Nick ! I wish it were different !!
Peter

[Nick]

Peter hi,

Don’t get too hung up on what the “noise” related objective are, these tweaks do aim at noise but they are also aimed at a wider target. In addition to the -144db breakthrough and reduction of noise entering the DAC from the PC but I have always had it in mind to take a detailed look at the NOS1 with a view to seeing if it can be tweaked for an even more enjoyable sound. The hunt for noise in this post and looking at the DAC generally have come together here. My motive is primarily to do this for myself to enjoy but if this can help the community gain more enjoyment I am happy to share findings.

Too many variables Nick ! I wish it were different !!

So far I have provided no real information on what I have done so proberbly not the best time for this comment due to the absence of information (now addressed below).

So whatever you come up with, at least to me it can't tell it all because it is not my situation. Nor anyone's else ... This, btw, also includes the being active of one oscillator only, which I dedicate much difference to begin with. Good stuff (for sure), but we all don't have that ...

I understand your point about a common config but remember my perception of SQ change is relative to these “baseline” mods already being in place. If needed I can place the standard NOS clocks that I have back in my NOS for comparison but Paul has spent several hours listening to my system as it currently is and could probably take a view on the recent changes, I think the NOS1 tweaks make a fundamental difference so I don’t think it will be hard to spot the changes at all for Paul.

In the far (far) end the only thing with real merit is to measure jitter (its characteristics) at the output. And here it stops I'm afraid (I am not able to do that myself).

I agree, the NOS tweaks are all about improving Jitter performance by improving supply rail conditions. Neither of us have the equipment to measure jitter (not many do given the cost of the kit needed), however I’v worked on many devices over the years (USB cards, DACs, CD Players Transports and Audio interfaces etc) almost without exception they have responded to PSU bypass tuning measures used here so I am not especially surprised by what is happening.

Below I have given information / my rational to target the tweeks but I have intentionally not given details of how to apply them to avoid problems with folks getting in to trouble trying to applying them.

So the tweeks to the NOS1 USB board and the DAC board and the rational applied.


The focus has been on selecting locations in the digital processing chain that are likely to benefit from improved power supply. The chain considered consists of USB decoder => FPGA => FPGA => DACs (I am excluding the Anadco in this post). We both are both probably comfortable linking this approach with jitter reduction. There is an element of trial here but it not entirely a “hit and miss” process rather it is based on experience informed by the information you kindly provided.

I guess the starting point has been working out what could be done to address the I2S related noise that we discussed earlier in the this post but also there has been focus on what might help sound quality.

The NOS tweeks and their rational.


Observations

The NOS USB interface has a single regulated 3.2 volt supply to power 5 IC devices which presents a challenge getting a responsive low noise supply to all the important supply pins of the ICs (eg supply pins that power key points in the digital signal train). In the past I’v have experienced improvements in sound quality all the way up to placement of 7 separate shunt supplies to power various rails on just 3 active IC devices within a DAC, probably overkill here, but you get the picture.
There is a total of 570uf of capacitance at the point that the 3.3v PSU connects to the USB board. I think that this large cap may present a relatively “slow” response to transient power demands and will dominate speed that the 3.3v rail reacts.

The level of rail decoupling capacitance on the USB board is on the low side of what I’v seen before on “audio” boards. The board ICs have a dozen or more supply rail pins on the 5 devices these are decoupled by a few caps generally of 4.7uf on the 3.3v rail. The 2.5v and 1.2v regulators have 4.7uf each in their output rails. There are also 100nf decoupling caps on many of the power pins. I guess this is not that unusual but I have found many times that more good quality capacitance in the right places can help significantly.

On the DAC board the FPGA (which receives and distributes the I2S to the DACs) has a an SMD 3.3v regulator, I cannot determine the exact amount of decoupling capacitance on the 3.3v rail as it splits to the FPGA power pins but the physical size of the SMD caps make me think it may not be a lot.

So NOS changes:

USB Board

1)   Remove the 470uf silmic and remain the 100u cap (I know this much capacitance may have been placed here for another purposes)
2)   Place 33uf of capacitance at C1xx which I think may be the point that the USB and FPGA chip rails fork. (Significant)
3)   Place 33uf of additional 3.3v rail bypass capacitance on the supply pin of the quadrant of the FPGA which is programmed to support I2S output processing. (Significant)
4)   Place 33uf of additional 3.3v rail bypass capacitance on the supply pin of the quadrant of the FPGA which processes the Audio oscillator inputs and distributes timing to the rest of the FPGA. (Significant)
5)   Add 33uf of additional bypass capacitance to the outputs of the regulators generating the 2.5v and 1.2v rails.

Only one of the targeted USB board cap placements i had in mind turned out not to improve sound quality and was reversed.

DAC Board

1)   Place 33uf of additional capacitance on the output of the 3.3v regulator that feed the FPGA on the board. This makes a very significant difference to SQ however I intend to tune the value further as I think 33uf is just a little to much in this location. The basis for this is a very slight drop in the remarkable top end sparkle that the USB board changes provide.

EDIT 19/09/2013 I dropped the cap from 33uf to 4,7 then to no additional capacitance. After careful listening the sound is best with no changes to the board here so I would not suggest anything here now.

That’s it….

First of all, to me it doesn't make much sense to put in Black Gates there. So, why do it in the first place but then with the focus on people not having them around. Thus, I'd say that any el cheapo cap will do the job here.

Regards the capacitors used, I happened to have Black Gates to hand. I do not want to heat stress and damage my PCBs so I do not want to be soldering and re-soldering to SMD pads and components so I went with the best caps I have which were the Black Gates. I have used Black Gates N Types may times for digital component PSU bypassing and got excellent results. I’m familiar with the likely SQ changes the Black Gates will give as they run in.

I really don’t want to get hung up on capacitor brands and types. My view is that the changes in SQ are so profound that I really think just adding the additional capacitance at these locations is likely to be much more important than the brand of cap used. The tweaks also happen to be cheap and relatively simple to implement, that ticks a lot of boxes for me. 

I am very happy for Paul and Mani to come have listen and compare my DAC with these tweaks at mine or in their systems if they are interested. This will give a second opinion on effectiveness of the changes.

Best to get the changes and rational on the table so we can have an informed discussion both knowing the details. Happy to discuss how all this might be addressing jitter but ultimately theory linking PSU noise to jitter spectra and our ability to measure jitter may run out quickly meaning that we may have to listen, trust our ears, and trust experience (uncomfortable though this may be). After all, were the current 4.7uf and 100nf decoupling caps on the USB board selected specifically for their contribution to reproduced sound ? I’m guessing they were more likely selected following recommended values in the Data sheet for the devices / good practice for general decoupling, and since Audio is a niche application for FPGAs and USB decoders etc the recommendations probably do not really conceder what works best in an audio application. Just a thought….

Regards,
Nick

Ps Anadco observations to follow.

EDITS were to grammar and one of the tweaked cap values was given as 3.3 uf not 33 uf as intended.

EDITS 19/09/2013 remove change to DAC board after listening test see above.

[PeterSt]

Thank you for (explicitly) sharing that Nick ...

Peter

[PeterSt]

Nick, I now realize that I wanted to say "thank you" for the Edits in there.

Peter

PS: But editing a post so much later isn't the best idea I think. But no worries.

[Nick]

PS: But editing a post so much later isn't the best idea I think. But no worries.

Peter,

Sorry, I agree it was a late update to the post. I did think about a separate post but I was also keen to make sure that the information was all in one place. In future if a similar situation comes up I will put a short post on the thread to say a change is made and edit the main material.

By way of an update, the USB card tweaks have been auditioned by another individual and I hope to get further subjective feedback soon. Feedback on the effect of the tweaks is the same as my comments about their effect.

I think there is something significant for sound quality here that could be worth a look. I will PM you some pics showing the detailed changes in case you would like to try the tweaks out for yourself (they are reversible and take about an hour to apply). Given the nature of the changes I strongly suspect that 80% of the "benefits" will be available using "normal" capacitors which would be very nice of it turns out to be the case. I would test this myself but I am not keen to stress my USB board with all of the de-soldering and re-soldering as I only have one to work with (or break  ).

Cheers,

Nick.

[PeterSt]

I can always send you 10 or so with a good discount Nick.
Haha.

But, interested of course ...
Peter

[Nick]

I can always send you 10 or so with a good discount Nick.

Thanks for the offer  I'll try to keep a steady hand with the soldering iron though haha

Nick.

[Nick]

I wrote part 1 of this post a few days ago and was going to post in the USB Cables.... Again thread but decided against it. Then after sleeping on the thoughts below decided to try something else which may add weight to the ideas on the effect of USB power supply noise put forwards below. Part 2 of the post deals with observations today.

Part 1

 I had a play about with isolating the 5v pin of my USB cable last night. Its something I had a go at quite a while ago with a diy platted silver usb cable and got "good" results at the time.

http://www.phasure.com/index.php?topic=1977.msg20341#msg20341

I tried "cutting" the USB 5v supply (using PVC tape over the pin in the USB socket),  and following this then went on to try replacing the PC 5v supply with regulated 5v and 3.3v supplied derived from inside the NOS1.

I though I would post some observations on sound changes and ideas about possible factors contributing to the changes.

First sound quality.

1) With 5v PC USB connected.

Boarder sound stage, fuller but possibly slightly less damped bass richer sound and tone.

2) Without 5v PC USB connection (USB power pin taped over)

Sound stage shrinks slightly but is sharper in terms of pinpointing individual sounds. Sound is generally tighter but slightly thinner, tone is not so convincing. Bass is better damped but the room ambiance form low frequency is not there possibly giving the sense that the sound stage has reduced in size.

3) With 5v PC USB disconnected but NOS generated 5v or 3v supply provided to the USB power input.

Sound is smooth but loses high frequency information which results in sound stage shrinking and a loss of perceived presence. This is very similar to the presentation of the Anadco fibre interface or the X-sound PCIe capacitance card.



My preference overall was easily listening with the PCs 5v USB connection in place. This is not what I expected. 



Some thoughts on what may be happening.

What does the 5v supply do within the NOS ? two things (and similar for other interfaces):-

• First it is used to pull up a bus enable signal into the USB chip (this does not appear to be needed because the NOS works fine without any 5v supply).
• Second and possibly important here is that the 5v usb supply connects within the NOS (and may other usb interfaces) into an anti surge protection chip that protects the d+ d- data lines of the USB interface connection from surge conditions on the USB connection.
  

The surge protection chip is a diode network that connects the d+ d- to the +5v USB supply and signal ground of the NOS. What all of this might mean is that conditions on the +5v supply wherever it comes from could link noise to the d+ d- signal lines ???

What is interesting though is that sound seemed better with the PC USB 5v line connected. This is what lead to the test replacing PC USB 5v supply with the NOS's own Internal supply voltages to see if a "low noise" 5v supply would have less influence on the d+ d- lines and signal ground. As reported above the sound was smooth and similar to having the 5v USB connection cut completely but still my preference was for using the PC USB 5v connection.

This is a stab here, but an idea that might to explain why the PC usb 5v supply sounded better than either no 5v connection or a "low noise" 5v connection, could be as follows. The noise level on the 5v line, wherever it is taken from is probably going to influence conditions on the d+ d- lines at the anti surge device.  However it may actually be better from a jitter point of view to use this PC 5v USB. it might be that the d+ d- lines may be carrying similar noise spectrum to the PC 5v USB line which might present as common mode noise on all three USB lines and not impact the d+ d- data transmission so much as it reaches the usb decoder chip. Alternately when using low noise 5v supply (from the NOS internally) any noise carried on the regulated 5v supply will not have the same spectrum as noise on the data lines and as a result may have a greater impact on the d+ d- transmission to the USB decoder chip.

This is just an idea to provoke discussion, I'v probably has a bit too much to drink here last night when thinking about this but thought I would post the ideas. It would be good to get to the bottom of what causes the differences heard.

Part 2

So today I wondered what would happen if the 5v PC USB supply were bypassed (smoothed) with capacitors at the NOS end of the USB cable. The answer turned out to be quite a lot happens and some potentially good stuff at that.

I added a range of capacitance values between the 5v PC USB supply and the NOS USB card signal ground. Observations on sound are as follows (note the NOS already has 100nf in this location so the values stated are in addition to this).

2200uf
Sound is smooth loses presence base is controlled and strong but sound is unbalanced with highs rolled off. Just like the regulated 5v and 3.2v supplies, a pattern forming perhaps.

470uf
Overall balance improving but sill nowhere near not having a capacitor for presence etc.

10uf
Still losing the harshness of the unfiltered 5v USB PC supply but still also not well enough balanced or detailed enough.

400pf smother sparkling top end mids and lows sounding good but transients are just a little slower than an unfiltered connection

220pf now we are really getting there. Hash gone, presence intact, beguiling sparkling highs, transients intact !

I'll try a few more values round 220pf and listen more but this is sounding very nice. It's a tuning point rather than extremely large change of the USB pcb tweaks but very nice all the same. Seems to give the sense of transparency and focus of lifting the PC 5v supply whilst keeping the life scale and tone of having the PC 5v supply connected.

I will post more thoughts after some more listening.

My guess is that the value of cap that gives good results will vary from system to system because it may be linked to the noise spectrum coming from a particular PC.

Nick

UPDATE 25.10.13

Looking at a few PCIe USB 3 cards most seem to use a DC to DC converter to take the PCIe 3.3v bus voltage and convert this to the 5v rail that is carried by the USB lead. So the cards i have looked have a SMPS running at 300 to 450 kHz straight onto the diode clamp mentioned above that terminates the USB d+ d- signal lines most DACs. For most of us the supply will just sit idle (supplying no current) 'humming' away on the USB card. The tests above showed that bypassing this 5v supply with a clean supply was not great. But what happens of the USB's 5v rail has some resistive rater than capacitive load applied to it ?

I put a 1k potentiometer between the USB 5v rail and the signal ground on the NOS1 interface. Having the load really help sound here. Best sound for me is around 200 ohms of load so around 25ma of current. If you try this be carful not to go below about 75 ohms as you will start approaching the 500ma rating of your USB card or mobo usb port (by 10 ohms load) and may get a hot potentiometer.

Sound quality changes with the resistance but is better in my system with a resistance in place. At 200 ohms there is subtle but important change throughout the frequency spectrum. Sounds like a slight reduction in jitter.  Bass takes on a more tuneful deeper and percussive feel especially.

The resistor seems to work well for both pcie usb and mobo usb.

I was wondering of the effect might be about countering ground loop current between the PC and DAC. I know ATx supplies tend to elevate the pcs signal ground a few mv with respect to PE and in my case my amp signal ground is connected to PE which could be making a loop from PC to DAC to amp. Whatever the cause the resistor is defiantly staying in place for now 


Regards,

Nick.

 

[acg]

Nick, that is an awesome post.  Very much appreciated.  The more that I get into this computer audio thing the more I realise that I don't know.  Regarding your capacitor auditions, I had a mental picture of Peter doing the same thing when developing the NOS1.

Cheers,

Anthony

[PeterSt]

Haha Anthony, you don't want to know. But most of these things can just be measured. And otherwise much is (my) theory only. Point is though : all these combinations (and different values !) are hardly feasable to test. So I really don't do that, but apply the theories.

Peter

[PeterSt]

PS: For fun look at the main PSU in the NOS1. All ready for all sorts of cap combinations. And not by accident. Nobody started working on that as far as I know ...

[PeterSt]

Hey Nick,

it might be that the d+ d- lines may be carrying similar noise spectrum to the PC 5v USB line which might present as common mode noise on all three USB lines

That. Or at least that is a good idea. But also outside of common mode noise it is a good thing to have one type of noise only, even if that's there two times.
So either way, I think this is a good hunch of you ...

Peter

[Nick]

Haha Anthony, you don't want to know. But most of these things can just be measured. And otherwise much is (my) theory only. Point is though : all these combinations (and different values !) are hardly feasable to test. So I really don't do that, but apply the theories.

Peter

Peter,

I really agree with you here, I dare not imagine how much time went in to tuning the DAC board ! Im looking at cap types but would not touch values its very obvious that there is design that's beyond me, so i'm not about to meddle haha.

The only change I did try  to a cap values on the board did not work (ref post above) !  .

Nick.

Edit - I selected the wrong post of Peters to "quote", it now reads as intended.

[Nick]

Hey Nick,

it might be that the d+ d- lines may be carrying similar noise spectrum to the PC 5v USB line which might present as common mode noise on all three USB lines

That. Or at least that is a good idea. But also outside of common mode noise it is a good thing to have one type of noise only, even if that's there two times.
So either way, I think this is a good hunch of you ...

Peter

Thanks Peter, I see what you mean. Im not sure about overall positive effects of the additional cap yet. I think some more listening and maybe changes to size are needed to decide.

Its interesting thought that at least in my system pc supply sounds better and that the attempts to "clean" the supply introduce such changes to the sound.

Im not sure it will lead to anywhere but fun to try out 

Cheers,

Nick.

[Scroobius]

Hi Nick - results so far of my efforts:

Part 2

.......... I wondered what would happen if the 5v PC USB supply were bypassed (smoothed) with capacitors at the NOS end of the USB cable. The answer turned out to be quite a lot happens and some potentially good stuff at that.

...............

220pf now we are really getting there. Hash gone, presence intact, beguiling sparkling highs, transients intact !

I have just tried 220pf and my system loses sparkle and life. I have some smaller values I will try tomorrow and will post the outcome.

Cheers
Paul

[Nick]

Paul hi,

This may not appear so but could be very useful information. As we discussed I think the effectivness of the cap in this position is likely to be specific to the pc set up being used. Let us know if other sizes work / what characteristics of sound they give.

Cheers,

Nick.

[Scroobius]

Hi Nick - After further listening more impressions of the 5v USB supply bypass capacitors. I have found it useful to solder an led holder (the type you "slide" the legs of an led into) in place so that capacitors can be slid in and out very easily for comparisons.

First of all I have made some changes to my system recently and it seems to me to be working very well. So I started this test thinking there is not a lot wrong at the top end to begin with. Anyway here goes: -

220pf - impressions tonight are the same as last night that 220 is too much and it dulls the top end to the extent that it appears to be robbing the music of some detail in the high frequencies.

100pf - similar to the 200pf but not quite as pronounced

22pf - this is interesting because it just seems to tidy to very high top end (which I did not really think needed tidying anyway) and to move at least some way towards the holy grail of effortless silky smooth strings.

Just now I do not feel inclined to remove the 22pf.

But I must say this is a subtle effect. Certainly this is nothing compared with other changes I have made recently.

Hope this helps.

Cheers

Paul

[Nick]

22pf - this is interesting because it just seems to tidy to very high top end (which I did not really think needed tidying anyway) and to move at least some way towards the holy grail of effortless silky smooth strings.

Just now I do not feel inclined to remove the 22pf.

But I must say this is a subtle effect. Certainly this is nothing compared with other changes I have made recently.

Paul hi,

Spot on ! This is exactly what I was hoping for. Most will not know but we both have very little desire to change the balance and presentation of the our systems right now.  This just seems to allow tuning of that small and persistant "sharp corner" in the highs. Its been remarkably difficult to tame without "filtering" using other methods to mask the problem but  in doing so sound is compromised elsewhere. This tweak seems to let the highs sparkle more but whilst not changing the sound elsewhere.

It's remarkable when you think that the cap you are using is just 20pf bypassing 100nf already in place. That's 1/5000 th of the main cap value. The devil as they say is in the detail.

I'm looking forwards to trying out some smaller caps in my system.

Cheers,

Nick.

[Nick]

Hi,


I've been continuing to look at the digital side of my system as part of my PC / DAC program of upgrades. Today's fun has been with the oscillator crystal on my NEC chipset USB 3 card. The standard oscillator on the card is a crystal and two capacitor resonant circuit. It's about the lowest cost setup. An order was placed for some low phase noise VCXO oscillators some time ago, they arrived earlier in the week, much of today was spent working on the PC USB card.


Results of placing the VCXO into the USB card have been as follows.


Case 1) VCXO replacement of standard crystal, power from the PCIe 3.3v supply.


Sound quality overall not as good as the standard crystal. The highs have real sparkle and superb crispness but sound lacks richness and bass in particular has taken on more of the "one note" quality that has been fixed recently. Don't get me wrong it's absolutely not down side everywhere but overall it not as good as the standard crystal.


Case 2) VCXO replacement using a LiFePo4 battery.


The idea here is to see of the PC supply is spoiling the performance of the improved VCXO oscillator (theories here are linked to the USB cable related post above). The result is significantly better. Bass and general richness is improved on case 1), top end sparkle not quite so good. So why is the system not better than the standard oscillator ? My hunch is that there is still a different noise profile in the PC's 3.3v supply and the battery and the USB chipset sees this on its crystal input, with this in mind onto case 3.


Case 3) VCXO replacement with the LiFePo4 battery now with the output of the VCXO feeding the USB chip via a decoupling signal transformer.


Now we are really getting there. The positives are the sound has so little to do with the speakers :-). Bass is excellent (percussive in quality) the sense of "realness" and presence in the room has taken a big step forwards. But the top sparkle is not as smooth as I would like and although realness his improved there is now only a very slight loss of richness (like replacing a rare NOS valve with just a good modern production vale in an amp). Case 3 is wired as a "lash up" using stuff to hand at the moment, so things may improve with more hours on the new "clock" and a more sensible layout and running in the capacitors used. Also I don't want to be using the battery in the long term so it needs setting up to use the PC supply.


So conclusions so far.


- Firstly the oscillator in the USB host card REALLY matters.
- For an oscillator to work well it appears that galvanic isolation really helps.
- There is potential here for a very big step forwards, there are "problem points" in the sound that I have been living with for years that went way today. Sound is not as balanced overall as I want but I think that can be done.


Last thought is that in the past I upgraded the oscillator at the music interface's USB decoder chip (eg the DAC end of the USB link) and that is where the biggest gains were found. I have a second VCXO ready to use in the DAC if the PC card can be made to work (and I can work up the guts, it doesn't look easy to fit).


I'll post updates, for now a few pics.


Nick


UPDATE 25.10.13

The first clock circuit was built using components to hand but still pointed at significant improvements in sound. I've been placing better selected components over the last couple of weeks and the results are now really great.

First change was replacing the audio note SPDIF transformer (which was to hand)  on the oscillator output for a good signal spec transformer and choke combination, this gave a really big change and then finally there are now decoupling caps of the correct size ether side of the signal transformer. Together this has really elevated sound quality.

Sound quality is now best described as getting real. There are a lot of other changes besides the USB interface mods above in this post now implemented in my NOS1. These and now with the new clock on the USB card have sound to most enjoyable levels. Even my duo speakers are playing some of the most precusive and tuneful bass I have heard. The sound stage just makes me smile at times, from stereo speakers it can be like listening to a 5.1 multi channel system at times people and instruments all over the place  .

For now the batter power on the USB clock will stay the drain is so low one cell lasts for days between charges and no problems creating a clean supply within the PC. I don't think this is the final stopping off point on the USB card setup but for now whilst work continues elsewhere this will more than do 

I'll post any further updates here.

Nick.

[acg]

Hi Nick,

Nice write-up.  I thought that I would share with you some photos of my PPAstudio USB card in the hope that it may give you some ideas or inspiration.  My card is a Version 1 card, not the Version 2.  The V2 is a recent item from Paul Pang that apparently has 95% of the sonic benefits of thie V1 card but is much easier to build which makes it cheaper.

You will notice in the photos the silver transformer and the upmarket TXCO as well as some little blocks of aluminium that Paul places on the card to try to control EMI/RMF a little.  As for the rest of it I am not so sure, but I thought you might have a clue.  I have posted before that this card is well ahead of the SOtM and Adnaco S3B (with linear supply) with my previous dac (I've not compared the mobo port to the PPAstudio card with the NOS1 - maybe I should) and that it can be powered with either the standard PC molex cable or with a linear/battery power supply.  To work the molex socket needs to be populated one way or the other.

Anyway, I hope this is of interest.  I will follow your pursuit with interest.

Regards,

Anthony

[CoenP]

Hi Nick

Why are you using a VCXO (Voltage Controlled Chrystal Oscillator)? These are used for PLL. It makes no sense to use them on a position with fixed frequency...

Regards Coen

[Nick]

Hi Nick

Why are you using a VCXO (Voltage Controlled Chrystal Oscillator)? These are used for PLL. It makes no sense to use them on a position with fixed frequency...

Regards Coen

Coen hi,

I realised that also last night :-) The spec on the vcxo is not too bad as it is but I think I will set the frequency  adjust pin to a definite potential. Could be that the floating adjust is why the sound is not quite as expected !

Im considering using a specialist clock module as the final set up. The Dexa clock I use in my NOS1 has transformer coupled output which  to but is not available in 24mhz frequency so may have to work something out there.

Cheers,

Nick.

[Nick]

Anthony,

Thanks for posting the pics of the PPAstudio card. It's interesting to get your impressions of how it compares to other setups like the SOtM and Anadco.

Will post back an update when / if I get the oscillator setup bedded in.

Cheers,

Nick.

[Scroobius]

Anthony - looks interesting how did you provide 5v for the card?

Cheers

Paul

[acg]

Hi Paul,

5v can be provided either from the computers power supply or preferably from a linear power supply or battery.  The maker recommends battery, but I don't want to go down that road, so at the moment I power it from my BeQuiet power supply.  I borrowed a high grade linear power supply in my pre NOS1 days and it certainly made a difference.  Like I said earlier I've not compared this card with the mobo ports with the NOS1 so I can't say if it has any effect, but that comparison is on my list of things to do.

The V2 card is US$129 with international delivery.

Cheers,

Anthony

[boleary]

Hey Nick, pardon me if this is overly simplistic and is something you've already done, but have you tried enabling and using one of the mb usb3 ports? Additionally, I disable the Renesias pcie card in device manager. For me it significantly reduces hash.

[Nick]

Hey Nick, pardon me if this is overly simplistic and is something you've already done, but have you tried enabling and using one of the mb usb3 ports? Additionally, I disable the Renesias pcie card in device manager. For me it significantly reduces hash.

Brian hi,

Not at all.
I am doing exactly as you say at the moment. Having worked on my PCIe card I'm using mobo usb3 as my standard setup at the moment. I find it beautifully smooth but lacking just a little presence. Very good for general listening though 

Regards,

Nick.

[boleary]

I find it beautifully smooth but lacking just a little presence.

At what SPL? Presence here "blossoms" between 88-92 db. If I had more presence, it would be surreal. Then again, I may be "curing" a problem with volume but the blossoming so increases SQ that I don't think so.

[Nick]

I wanted to keep the information together in-context so i'v posted a couple of updates to the post on the 5v USB cable supply voltage.

http://www.phasure.com/index.php?topic=2640.msg28369#msg28369

and the post on building a replacement oscillator for a USB PCIe card.

http://www.phasure.com/index.php?topic=2640.msg28522#msg28522

The updates are in blue text.

Both have posertive effects on sound quality (well here at least  )

Cheers,

Nick.

[Nick]

I want to close out comments on the Anadco fibre USB extension system that I made here.

http://www.phasure.com/index.php?topic=2640.msg28094#msg28094

At the time of the post tweaks to the Anadco were improving its performance significantly. However, I now don't think that the Anadco can be made to equal or exceed the sound quality performance of a direct USB connection  (assuming there are no major electrical / noise problems with the direct USB connection). 

With an unmodified PC USB interface and NOS1 the Anadco could not be made to better the direct connections performance. With the clock upgrade to my PCs USB card and the upgrades made to my NOS1 the Anadco cannot get near the performance of the direct USB PC to DAC connection.

So the conclusion here is again the same that Paul and I reached when we tried the Anadco system in both of our systems a year and a half ago. I guess that the benefits of galvanic isolation of the USB link between the PC and DAC are outweighed by the complexity / jitter introduced in to the USB link by the Anadco.

Worth a try bit the Anadco system goes back on the shelf 

Nick.

[PeterSt]

But that is sad news Nick ! And you were so enthusiastic about it (for the second round) ...

But did you use a more decent power supply for it now ? I assume yes of course ...

Peter

[Nick]

But that is sad news Nick ! And you were so enthusiastic about it (for the second round) ...

But did you use a more decent power supply for it now ? I assume yes of course ...

Peter

Peter hi,

Yes I tried a variety of PSUs and a shorter 1m fibre cable but just could not get it to be as effective as direct USB. In the end though its been a useful part of the journey, adding to the understanding that reduction of jitter in the PC to DAC USB connection is more important to sound quality than galvanic isolation of the USB connection.

On another subject I spent half a day building a transformer isolated I2S lead last weekend to try in my NOS. I was not really expecting it to be successful given the link speeds but though it would be fun to try. At 16x up-sampling I managed to get reasonably good electrical wave forms across the lead but I think the rise times of the transformers put the data streams out of sync. I did get some music playing (which was very surprising  ) but under a massive layer of static.

I might spend a bit more time with it to see if I can pin down specifically what is happening. Also it might me fun to try at different upsampling rates just to see what happens.

Here's a couple pics of the "creation" 

Regards,

Nick.

[PeterSt]

Haha, I can show you similar pics Nick; can't work. All these means (and the digital ones for sure) only add jitter if you can get a good signal from analogue to begin with. But really, an anlogue transformer is too slow. This is not related to the sampling speed. You will always get "rounded" "waves" while it should be square.

It can be done though, but the how is a big .

Regards,
Peter

[Nick]

It can be done though, but the how is a big .

Very nice  could that be on a piggy back board or built into a lead  haha 

Nick.

[Nick]

I mentioned above that the NOS1's USB interface 24mhz clock has been on the list of items for attention.

I bought a smd rework hot air station to help install a clock upgrade last week and got stuck in this weekend. I built and tested a 24mhz replacement clock from a VCXO with LiFePo4 battery power and transformer decoupled clock output yesterday. The standard NOS1 crystal clock and other components were removed and the new clock installed today. As expected the clock really dictates sound quality.

How does it sound ? With a few hours on it, its a HUGE change. I think the impact is proberbly magnified by the 6 modifications made to my NOS and PC's USB card but having said that this clock change has bigger positive effect on sound than ALL of the other changes put together and by a LARGE margin. Music has such a live quality, bass is so extended and tuneful there is such a sense of performance it's a massive step.

Today Iv been playing track after track of the harshest fastest most complex most difficult music I own. The stuff you put on to really test your system. In my case this stuff usually delivers a nugget of diapointment as the system falls apart here, there and everywhere. This afternoon has been very different. Nothing so far has tripped the system, playing this seat of your pants complex music is now simply riveting listening. And the clock is getting beter by the hour as it runs in. I knew that clock was going to be important but I'm shocked by the size of this change.

Next up is to decide how the final PC USB and NOS1 USB clocks are going to be setup. And turning the system again, the change is very large and I think PC Bios and XX Settings will need tuning to suit.

Paul is due to visit my place soon so it will be good to get his opinion.

A very happy Nick.

[acg]

Hi Nick,

WOW!!.  Please provide some more details and photos.  I am interested by your battery solution.  Are you considering a super low noise linear psu as a more permanent solution or do you think you will persist with the battery?

I have access to a SMT oven and a hot air gun here and could probably duplicate your work and provide a second opinion if you like.

Cheers,

Anthony

[PeterSt]

Hi Nick,

Replacing that 24MHz with something better does not really make sense to me. Or not yet ... 

You shouldn't have replaced these two components at the same time with the suggestion that the "clock" makes it for the better.
Small problem of course : how to make that original crystal run from a battery ...

Anyway, without real further investigation I say that it is the supply noise you got rid of. Nothing about the clock itself.

For others : It may not be fully clear to you, but this is not about the clock(s) to the DAC; this is only about the USB interface.


In the mean time I am "able" to theoretically (!) see how even this USB transfer oscillator(s - PC end as well ... although ... maybe not that one) can contribute to jitter. So, not talking about noise incurring for this jitter, but just the oscillators and their own jitter spectrum. Well, *that* would be something new.

Nick, how easy is it for you to use this new oscillator but now grab a normal nearby 3.3V from the USB board (hence don't use the battery) ?
Judging the result could be difficult because the low noise battery supply will be a first thing what helps. Still (and contrary to my first sentence in this post) I have the hunch that it is the clock itself you are hearing. So what if the result stays as good with the normal 3.3V supply ?


Next step : feed the whole USB interface with that battery. It's only that you shouldn't plug in the USB cable too often while that will suck a few hours of normal operation because of doing that. Switching on (also the PC) same story.

Peter

[Nick]

Pater hi,

Jut a quick response for now, ill have to come back in more detail later today.

There is only one change to the NOS USB board, the extra components I mentioned that were removed are the resonator capacitors which are part of the clock circuit so I'm commenting on only one recent "change" which is the clock replacement.

I can try using the NOS USB interface 3.3v supply easily so I will give this a go. I am very sure that this is not about power however, so I'm not anticipating a significant change. I think this is a jitter improvment. Ill post back my thoughts about what is happening later.

Best,

Nick.

[PeterSt]

I am very sure that this is not about power however, so I'm not anticipating a significant change.

Nick, maybe I should emphasize that I think the same (my post started out a bit confusing). At least I hope you won't find a significant change ...

Thanks !
Peter

[acg]

Peter, do you know off-hand the voltage and amperage draw of the USB board?  This is the board that the 3A supply feeds is it not?

Anthony

[PeterSt]

Anthony,

I especially forgot the figure needed for plugging in the cable, and all I know is that the 3A PSU is in there because it was used in the predecessor of the NOS1-USB which needed 1A as far as I recall. But 1A it won't be because that this beyond USB specs (what it that ? 500mA ?).

The continuous usage while playing fits your observation of something like 20mA (see XXHighEnd PC topic). But the real figure will be shown by the USB port (concerned) properties. So what's listed in there was my own observation back at the time (and the reported figure in the USB port's properties are official; notice though that this is not real time judgement of the OS - it is the figure put in there by myself ...).

Peter

[Nick]

Peter hi,

I only had time for a partial reply earlier so to expand a little...

For others : It may not be fully clear to you, but this is not about the clock(s) to the DAC; this is only about the USB interface.

Agreed, this is the 24Mhz USB 3 receiver clock on the NOS1 USB interface (not the audio 22Mhz and 24Mhz audio clocks on the NOS USB board already work great).

You shouldn't have replaced these two components at the same time with the suggestion that the "clock" makes it for the better.
Small problem of course : how to make that original crystal run from a battery ...

I’m not sure exactly here about the thought that two thing have changed, The only components replaced on the USB interface PCB are the standard 24Mhz clock crystal and the resonator capacitors for the clock crystal.  I think the (battery) power supply change is not very important but I will try powering the new 24Mhz clock from the 3.3v power supply used for the NOS USB interface PCB just to see.

The existing clock is a crystal driven by the USB chip not a active clock module a so it not possible to power the existing clock arrangement with an "external" supply (battery etc).

Replacing that 24MHz with something better does not really make sense to me. Or not yet ... 

Anyway, without real further investigation I say that it is the supply noise you got rid of. Nothing about the clock itself.

In the mean time I am "able" to theoretically (!) see how even this USB transfer oscillator(s - PC end as well ... although ... maybe not that one) can contribute to jitter. So, not talking about noise incurring for this jitter, but just the oscillators and their own jitter spectrum. Well, *that* would be something new.

My thought is that this does come down to Jitter in the end but in the digital processing domain which must ultimately somehow result in jitter in the audio data stream. I think we are all resonably comfortable that you can influance jitter in the software domain from within XX so it did not seem a big step to assume that data hardware might be able to as well.

The thoughts below are very circumstantial but its possible to see how important the 24Mhz clock and derived frequencies are to the async USB link and moving data downstream into the FPGA.

My first reason for trying an upgraded clock is that as mentioned earlier in the thread I have re-clocked USB receivers on Audio interfaces in the past and had significant changes to sound quality. This would probably have been enough to try a new clock but the NOS USB PCB proberbly a very  expensive board and I did not want to commit to a possibly irreversible change without at least some research into what the 24Mhz clock drives and the areas that might be impacted by an improved clock.

This is what jumped out from data sheets.

• Looking at the NOS USB transceiver chip (I cannot get hold of the NEC USB Chipset datasheet), the USB transmitter multiplies the 24Mhz frequency by 20x to generate the 480Mhz USB 2 standard line transmission “clock”.  I guess that phase noise in the 24Mhz clock can really impact the X20 process and the stability of the 480Mhz derived transmission clock.
• The 24Mhz clocks at both end of the USB link (NOS and PCIe USB 3.0 card) will not be at exactly the same frequency (10s, 100s or 1000s of beats per min out, I have actually tried but failed to tweak my oscillators to match the crystal speeds  ). Could the receiver at both ends of the USB link be using somthing like a PPL to “clock in” received data. If this is the case the more stable data speed arriving the lower the chance of the PPL hunting or losing its lock ?
• To generate a 20x clock 480 Mhz transmission clock speed (or PPL lock if they are used), the phase accuracy of the 24Mhz source clock is going to very important. The standard clock is a simple sine wave oscillator with relatively poor phase performance. When compared to a low phase noise clock the standard crystals sine wave means accurate phase triggering must be hard for the USB chip and noise in the detection circuit of the USB chip can create a relatively large time shift in the detected clock edge.
• Final thought is looking down stream from the USB cards usb transceiver chip to the FPGA. I don’t know how the FPGA code is designed and therefore which source clock drives the data handling within the FPGA. I would guess that some of the FPGA could be slaved to frequencies derived by the 24Mhz USB Clock.

I could not really give hard arguments about the points above they are as likley to be wrong as right but it just felt like the 24Mhz clock was important enought to try an upgrade. Power supply and electrical noise might come into the overall equation but the change in sound is just too fundamental IMHO. It would be the biggest “noise” clean up tweak ever if it were just this alone. Whatever the cause,  the change in sound quality is defiantly for the better and IMHO is really, really large. I was rocked on my heals again this morning when I played a few more tracks.

I’m happy to send the implementation details off-line Peter if you would like them (its not too complex really but might help if you want to try it out), I don’t know if you have tried the capacitor modification to the USB board yet but the clock change is really is worth some time.

Best regards,

Nick.
Edit - language tidy up

[PeterSt]

Nick, not responding to everything ...

Sorry about the confusement about my "two components" but I really meant the oscillator as one component and the noise-free battery as the other, while knowing that you couldn't apply the battery-only to the crystal. So that's how I thought to test it the other way around, and apply the normally 3.3V supply to that better oscillator. In the mean time though I changed strategy (in my first post about this) and thought that it wouldn't be the noise making the difference but just the oscillator. So this would even justify trying the normal 3.3V supply. It would prove it is the oscillator doing it.
Of course I did not know that you were on that track too ...
So all consensus.

Meanwhile, already yesterday I thought to replace the oscillators at both ends with just the 24.xxx audio clocks. Haha. I think it will just work. What do you think ? So I wanted to suggest that to you, but you have one of those only (spare, I know ).
Next it is not so easy for me at this time because I'd need to replace the oscillator on the MoBo. Can be done, but is not the most convenient of course. So ... what USB3 interface do you suggest ? Should be normal PCI (not PCIe) or otherwise I can't get it in.

And oh, my thoughts on the software being able to influence and from there think about this (still asynchronous !) interface to tweak are again the same as yours. The "why" I am not sure about at all at this moment, but all further theories tell me that there's some work to do here. All quite new ...

So far for now !
Peter

[acg]

So ... what USB3 interface do you suggest ? Should be normal PCI (not PCIe) or otherwise I can't get it in.

Peter, the Asrock mobo has 3 x PCIe slots and only 1 x PCI slot.  I understand that the silent video card has the heatsinks and takes up a couple of slots, but can't you move it to the slot furthest from the CPU and then slip in a PCIe card behind it?

As far as cards go Peter, I would recommend you try two...a standard USB based on the NEC Chipset and the PPAstudio USB3 Card.

Cheers,

Anthony

[PeterSt]

Anthony,

So that PPAStudio is SOtM based ? (sorry I didn't look at it earlier)
Then nothing for me. Already not because it needs a driver (as it looks). High latency and such.
The mod may be nice, but this card in general is not advised. Well, not by me.

Regards,
Peter

[CoenP]

. So ... what USB3 interface do you suggest ? Should be normal PCI (not PCIe) or otherwise I can't get it in.

AFAIK PCI is not fast enough for USB3. At least not for the common two port USB3 cards.

regards, Coen

[acg]

Anthony,

So that PPAStudio is SOtM based ? (sorry I didn't look at it earlier)
Then nothing for me. Already not because it needs a driver (as it looks). High latency and such.
The mod may be nice, but this card in general is not advised. Well, not by me.

Regards,
Peter

Nothing to do with SOtM and a much better product.  It is simply a standard USB3 card based on a specific NEC chip that has been upgraded withe better TXCO and a little transformer among other things.  You don't need a driver, but the NEC driver can be used if you wish.

[PeterSt]

Thank you for elaborating Anthony.
What I don't understand then is why the link you gave shows "SOtM" on the PCB plus those downloads are offerered.

Peter

[acg]

Peter, I think that SOtM is on that PCB because he is saying "I do all of this in one little chip instead of this whole board".  Paul is Taiwanese and his English is not great but is getting better all the time.  The downloads are the specific drivers from NEC for the USB chips on the card and they can be used or not used.  I use the recommended driver but I can also just use the generic driver bundled with Windows 8 and it works fine.  Note that there is no USB3 driver native to Windows 7 so perhaps the driver may be specifically targeted at those not using an o/s with native USB3 support.

Regards,

Anthony

[acg]

Please note also Peter that Paul Pang recommends 5V 1A minimum external power for the card which is 900mA to meet the power output of the USB3 specification (that is never used in our situation as far as I can tell) plus 100mA to run the card itself.  When I measured the power draw of this card in the Linear PSU thread it never drew more than 20mA when it was connected to the NOS1.  You could use a super low noise/low power psu for this card.

Also, Paul also upgrades motherboard clocks with what seems to be the same clocks as used on his USB card (see picture below) and he also has a modded CF card reader that can be used as the O/S disk instead of a SSD or HDD.

All food for thought if we are thinking about the clocks in general.

Anthony

[PeterSt]

Aha ...

Ok !
Sorry to be a confusing pain ...
Peter

[Nick]

Nick, not responding to everything ...

Sorry about the confusement about my "two components" but I really meant the oscillator as one component and the noise-free battery as the other, while knowing that you couldn't apply the battery-only to the crystal. So that's how I thought to test it the other way around, and apply the normally 3.3V supply to that better oscillator. In the mean time though I changed strategy (in my first post about this) and thought that it wouldn't be the noise making the difference but just the oscillator. So this would even justify trying the normal 3.3V supply. It would prove it is the oscillator doing it.
Of course I did not know that you were on that track too ...
So all consensus.

Meanwhile, already yesterday I thought to replace the oscillators at both ends with just the 24.xxx audio clocks. Haha. I think it will just work. What do you think ? So I wanted to suggest that to you, but you have one of those only (spare, I know ).
Next it is not so easy for me at this time because I'd need to replace the oscillator on the MoBo. Can be done, but is not the most convenient of course. So ... what USB3 interface do you suggest ? Should be normal PCI (not PCIe) or otherwise I can't get it in.

And oh, my thoughts on the software being able to influence and from there think about this (still asynchronous !) interface to tweak are again the same as yours. The "why" I am not sure about at all at this moment, but all further theories tell me that there's some work to do here. All quite new ...

So far for now !
Peter

Peter hi,

Time is a bit limited this afternoon, but there are a few points that I need to highlight to help get good results and I can see that thoughts are running on quickly in the post.

Regards the PC USB board.

I would go for a NEC chipset PCIe USB 3 board they are cheap and easy to replace the clock on. If it helps I will send a link to the one that I have modified later.

A key point to getting the best performance here is that both the NEC chipset and the 5v USB aux supply need to be powered by the PCs internal supply (this seems the wrong thing to do but sound is better). Just plug the board into the PC PCIe slot as usual to do this, it’s only the clock that need to have a “good supply”

Next is the new 24Mhz clock for the USB board. This needs to be transformer and capacitor decoupled on its signal output. Decoupling like this means that there is no problem with the USB Chipset (on the PC supply) and the clock using different power supplies. If the clock signal is not transformer decoupled the differential noise between clock supply and USB chipset (pc) supply effects sound quality. Even using a Battery to power the clock will not give best sound if the clock output is not transformer decoupled.

I can send you details of a suitable pulse transformer and capacitors to set up the clocks output.

You could use the PPAStudio USB board but if you do I would suggest using it with the PC supply connected to the molex (Paul and I have been corresponding on this there are other options for the clock but that means changing the board)

Regards the use of 24.xxx clocks

I did think of this as well but needed to place an order anyway as I only have one of the 24.xxx clocks, so I went for the 24.0Mhz VCXOs. The only reason I can think of that 24.xxxMhz clocks might not week is if there needs to be a  sync of some sort with the PCIe bus speed and 24.0 is needed for this. Worth a try though because the 24.xxxMhz clocks you use have top class phase performance.

For information I will send you the details of the VCXO I used although I have found a much better spec 24Mhz TCXO for Phase performance which I will also send.

About the NOS interface.

Here again its important that the new clock needs to be transformer / capacitor decoupled from the NOS board to separate the clocks power supply from the NOS USB PCB supply. Even using a battery to power the clock will not give the best results.

I am sure that you will be fine working out where to inject the clock signals onto both the PC USB board and NOS USB PCB  but if it helps I can PM you some pics.





I have not got time right now to expand on why some of points above appear to be important, but they have been subjectively tested and these points do make a BIG difference to the results.

I just wanted to nudge thoughts in the above direction if you are already working on this. Happy to discuss more this evening.

Best,
Nick.

[PeterSt]

So ... what USB3 interface do you suggest ? Should be normal PCI (not PCIe) or otherwise I can't get it in.

Peter, the Asrock mobo has 3 x PCIe slots and only 1 x PCI slot.  I understand that the silent video card has the heatsinks and takes up a couple of slots, but can't you move it to the slot furthest from the CPU and then slip in a PCIe card behind it?

Hey Anthony,

I made some wrong assumption and it now (since I finally looked) appears that we left both a PCI and a PCIe slot accessable. The video card + heatsink occupies the middle two (PCIe) slots.
So all good to go in either direction.

Thank you for your help.
Peter

[Nick]

Hi Nick,

WOW!!.  Please provide some more details and photos.  I am interested by your battery solution.  Are you considering a super low noise linear psu as a more permanent solution or do you think you will persist with the battery?

I have access to a SMT oven and a hot air gun here and could probably duplicate your work and provide a second opinion if you like.

Cheers,

Anthony

Anthony hi,

Sorry its taken a while to come back on this, I will PM you.

Cheers,

Nick.

[Nick]

Peter hi,

Meanwhile, already yesterday I thought to replace the oscillators at both ends with just the 24.xxx audio clocks. Haha. I think it will just work. What do you think ? So I wanted to suggest that to you, but you have one of those only (spare, I know ).

This looked like a great given the excellent performance of the 24.xxx clocks so I bought a second 24.xxx clock last week and did some testing.

Results here were that I managed to get the PC USB pcie card to recognise a USB stick drive with the 24.xxx clock fitted. However the NOS USB interface with 24.000 mhz clock fitted would not connect to the PCIe card fitted with the 24.xxx clock.

Next I tried to fitted a 24.xxx clock to the NOS USB interface pcb and tried again to see of the 24.xxx clock at both ends of the link would help. Unfortunately I still could not get the NOS interface board to work (the usual green "USB" LED would not light up.

This is a real shame because the performance of the 24.xxx clocks is I another league to what seems to be available for 24.000 MHz clocks.

I did get in a bit of a fix with a battery which was not charged so it could still be that the 24.xxx clocks might work but I reasonably sure that the result is a sound one.

Did you fair any better with your tests on the 24.xxx MHz clocks Peter, has it worked with you ?

Cheers,

Nick.

[PeterSt]

To be honest Nick, I today thought to maybe get something to work day after tomorrow. But since your report I think I better skip that excercise ? Of course I never dove into USB specs concerned, but still I would have thought it should work.
Next step could be to find 24MHz oscillators with the most good pecs.

Not sure whether we should try to outbetter your attempts ...

Peter

[acg]

To be honest Nick, I today thought to maybe get something to work day after tomorrow. But since your report I think I better skip that excercise ? Of course I never dove into USB specs concerned, but still I would have thought it should work.
Next step could be to find 24MHz oscillators with the most good pecs.

Not sure whether we should try to outbetter your attempts ...

Peter

My vote is for you to try Peter.

[Nick]

Peter hi,

Unfortunately I don't think that the 24.xxx clocks will work, but I would be delighted if they could be made to. Its worth mentioning that the wave form I had from the 24.xxx clocks via decoupling transformers was not the best, quite some overshoot but well damped recovery. I don't think this is the cause of the failure of the 24.xxx clocks but its worth a mention. The clock waveform is on the list of stuff to be looked at on the 24mhz clocks as the waveform also overshoots but not quite so much.

I did have the thought that although the 24.xxx clocks don't work might the 22.xxx audio clocks work ?? I only have one of these to hand and had other testing planned for it so I was not planning to try the 22.xxx clock out here. Perhaps these would be worth a try at yours ?

Small performance variations in the 24mhz clocks being used here do appear to have an impact on sound quality. The state of charge of the battery powering the clocks can be heard for instance. I think this is good however because the the VCXO I'm using only has goodish phase performance which I hope means that further clock improvements could improve sound even more, that would be quit something. A friend of ours has a rather higher phase noise spec (but expensive) 24mhz TCXO to try out. It will be interesting to see what the results this produces compared relative to the VCXOs iv been playing about with.

Cheers,

Nick.

[PeterSt]

Thank you for that feedback Nick.

Today a Nec based USB3 PCIe cards will arrive (and in a few days another one/type) and we will try. It always depends a bit on priorities - with some related experience on the Adnaco, right ? (read : some things never happen).

In the mean time I think this whole "noise" issue is a loose running train. Post coming up about that soon ...

Peter

[Nick]

Hi,

An update on USB clocks.

As mentioned above the battery powered TXCO have really been useful in proving to me the value of improved clocks for the transmitting and receiving end of the USB audio link. Messing about with the clocks and with Paul's Paul Pang USB Card showed that there is headroom for sound quality as qlock quality is improved. With this in mind what things have changed again and I hope will be the final stopping off point is now in place.

I ordered a couple of reference quality 3rd party upgrade clocks (Dexa Neutron Stars, that brings the total to 3 of them now in my system !) in special order 24mhz frequency. These are now fitted to the PC PCIe USB card and the NOS1 interface together with matching separate high quality mains powered Dexa linear supplies for the clocks.

What were the results ? Well things are running in so I’ll come back with an update if needed. For now this is what was done and the sound quality changes.

The clocks were put into the music system one at a time to get a feel for their impact.

USB PCIe reference clock.

Putting the reference clock on the PCIe USB board improved sound quality a lot (again  ). The Dexa delivers the smoothness and tone of the Paul Pang card with the bass extension and drive of my DIY clock. In addition it extends, cleans, and tidies up music top to bottom. The surprise was the dynamics which are much closer to real presentation very enjoyable to listen to. I would say that the required volume XX setting for a listening given sound pressure level has lowered buy 1.5 to 3 db (eg -33db now sounds like -30db did before) this seems to be down to a much richer and fuller sound but still with detail and not at all congested.

NOS1 USB interface (USB 24mhz) clock added to the above

With the reference clock applied to the NOS USB interface as well as the PCIe USB card things get interesting. Tone especially is much improved, very convincing and easy to listen to for hours. Again hash (that you would not really have pointed out before at all) drops away. Ability to sort out difficult congested tracks is great (there is nothing right now that I can really say trips the system up badly), is like a major cartridge upgrade on a vinyl set up. The system “tracks” the complex and makes much better sense of it.

Now the interesting part with all of this perceived improvement there is a slight reduction on dynamic presentation. Its very slight and I take this to be a good thing. Jitter can falsely increase the perception of dynamics and it sounds to me like what is playing now is much more realistic so Ill keep an eye on this.



With the two changes above in place XX software settings are not nearly so sensitive as before but at the same time different settings are needed. Next step is to tune the software parameters suit the new response of the "down stream" system.

Ill update more as things settle in. For now having made a considerable investment in these clocks on a hunch I can say that I am delighted by the results and there is absolutely no way having heard this that they would come out of the system again.

Now onto packaging of the new components, my poor NOS and PC are looking a like electronics projects at the moment 

I know that Paul has also invested in one of these clocks so it will be great to get Pauls impressions as well when he has fitted it.

Cheers Nick.

[Scroobius]

Hey Nick - how about a photo of your rig as it is just now?

As Nick mentioned a Neutron Star dropped though my letter box last week watch this space .................


P

[Nick]

Now the interesting part with all of this perceived improvement there is a slight reduction on dynamic presentation. Its very slight and I take this to be a good thing. Jitter can falsely increase the perception of dynamics and it sounds to me like what is playing now is much more realistic so Ill keep an eye on this

Hi it turned out that I had a stray mains lead that had folded over the area of the crystal can one of the clocks. This was removed and dynamics now back to where they were when the pcie usb card clock was installed. These clocks are not cheap, but what a sound 

Nick.

[acg]

Thanks for the report Nick.  The particularly interesting part for me is that you report that the "tone" has changed...if what I call tone is the same as what you call tone then this is a profound change.

My major gripe with an external clock such as the DEXA is that it is removed from the USB board and the clock signal must travel by wire a certain distance to where it is required and hence becomes more sensitive to inducting noise.  Two steps forward...one step back.  The ideal way here would be to incorporate something like the DEXA clock into a redesigned USB board, but only Peter could manage that sort of an upgrade.

I really look forward to Pauls impressions once he has his DEXA clock installed.

Anthony 

[Nick]

Anthony hi,

I agree improvements in tone are hard won. Its changed so much particularly with the clock changes. Paul and I have spent a lot of time debating  these changes in tone reproduction,  its often now the first quality of sound that we discuss. It just seems to be so important in digital reproduction particularly with NOS DAC types.

The dexa signal lines are  better than  the set up we discussed offline, in that the signal is connected via smb coax so there is good noise shielding. The coax runs are  25cm at present but they will get much shorter when the packaging happens.

Kind regards,

Nick.

[PeterSt]

Hi there Nick,

I would say that the required volume XX setting for a listening given sound pressure level has lowered buy 1.5 to 3 db (eg -33db now sounds like -30db did before) this seems to be down to a much richer and fuller sound but still with detail and not at all congested.

Earlier I wanted to "state" that to me this tells the opposite of "good", but I stayed out of it.
But regarding your one but last post I am tempted to say this again and now I do.

What about listening for a week before posting "conclusions" ? I think that will help.

Regards,
Peter

[CoenP]

With the two changes above in place XX software settings are not nearly so sensitive as before but at the same time different settings are needed. Next step is to tune the software parameters suit the new response of the "down stream" system.

Hi Nick,

I think this is most interesting. It could be for better or for worse that the sound is less "tunable" by the PC. "Better" is not allways for the better in my experience!
I would suspect that the clock in the DAC contributes most to this effect. Did you try if there is a difference?

Looking forward to more reports about thise clockreplacements,

regards, Coen

[Nick]

Hi

Well things are running in so I’ll come back with an update if needed.

There is a little over a week of time on the clocks now. From experience they burn in quite quickly so whilst there will still be changes other factors like packaging are likely to have a greater effect on sound now that burn in.

So how do the clocks sound ?

Well first thing to sat is that these changes are very large, what is being described are not subtle or small changes. This is structural stuff, everything changes, with the overwhelming feeling of positive change.

• Sound is like listening to very high quality vinyl. There is virtually no sense of digital replay. The image is detached from speakers but remains rich a realistic. There is a significant improvement in tone at all frequencies from, bass notes that are much deeper, better damped and tonnaly defined up to cymbals that you can here the size and nature of the disc that has been struck. The tone of voices is just beautify presented.
• There is an effortless feel to the way that the system delivers energy into the mix. Crescendos go loud in proportion to the rest of the music. Micro and macro dynamics add the feeling of live musical presentation.
• When playing problem tracks I can relax into the music knowing that it will not collapse when the music gets loud and complex. The system just "tracks" trough it all unpicking the strands and maintaining richness image and tone as it all blasts out. Grunge Rock has never sounded so right here for instance.

Summarising the change in sound is fundamental, it is much much more real sounding than before.

Having heard these differences I think there are a few points to reflect on.

After applying the USB clocks i'm convinced that for many years we have been listening to the characteristic of the audio data being transmitted over USB links. There is a very large audible signature associated with USB and the signature is very profound in terms negative effects on how the DAC process operates after a USB transmission.

The clocks almost certainly wont perfect the performance of the USB link for audio, but the audible USB signature is massively reduced with the application of the 24Mhz clocks.

There is another factor in the case of the NOS1 which is that the FPGA chip that comes after the NOS1 USB receiver Chip must be at least in part slaved to the 24mhz USB clock so there is likely to be an improvement in processing here too. 

I think that without so much signature USB effect, XX software settings are more subtle in their effect but there is more logic and repeatability in how they effect reproduction. This is great because although in absolute terms their effect is not so great, they still make differences and can REALLY polish elements of the sound.

I know that a couple of other forum members have heard the effect of the upgraded 24mhz clocks and have equally strong views about their impact.

Finally the extremely welcome surprise this week has been that Peters new Q5=1 setting adds very significantly in almost exactly the same way to sound quality as the clock upgrades. WOW that was a nice surprise 

Regards,

Nick.

[PeterSt]

Hi there Nick - Nice stuff !

Of course in the other (SQ) topic I wanted to ask how you could compare the electrical amendments (clock) vs the software one (Q5). So could you really do that ? Or does the Q5 thing just adds more of the same goodness ?

Regards,
Peter

[Nick]

Hi there Nick - Nice stuff !

Of course in the other (SQ) topic I wanted to ask how you could compare the electrical amendments (clock) vs the software one (Q5). So could you really do that ? Or does the Q5 thing just adds more of the same goodness ?

Regards,
Peter

Peter hi,

My feeling is that the q5 goodness is very similar in effect to the clocks effect but its difficult now for me to isolate the effects one by one, however  ....

I know one of our member has both a dexa clock modified dac (running in)  and a standard NOS1 available right now. We were chatting about the clocks and also the  q5=1 setting last night. This might be a good opportunity to compare q5=1 and clocks. Personally i think they do move in the same direction.

Regards,

Nick.

[AlainGr]

Hi Nick,

I am still following you, even if I don't post (over my head). But the way you, Anthony, Paul and Peter are preparing the table, I feel it will be a feast for the ears we will remember for a long time !



Alain

[Nick]

Anthony,

Nice idea I had not thought of looking at a cf-sata adaptor, iv been looking at hdds so far. Ill take a look at cf-sata adaptors as well 

Nick.

[Nick]

The aim of this thread is to report activity that concentrates on finding / addressing  digital and analogue noise in the pc and dac playback system. The following post was made here on the basis that the effects it describes may relate to unwanted signal components (noise) introduced or omitted by the transfer of data between pc subsystems and my usb dac.

For continuity in my reporting in this thread I have linked to the post which was moved to a new location without reference to it being made here.

http://www.phasure.com/index.php?topic=2784.msg29291#msg29291

[PeterSt]

My apologies Nick. I should have done that. It was even so that someone asked me where all went, and I recall that I answered in a fashion "wasn't this obvious then" ? But all I did was adjusting one of the posts in there saying "I have moved this from ..." and plainly forgot to tell similar in here.

Good that you did this.
Peter

[Nick]

My apologies Nick. I should have done that. It was even so that someone asked me where all went, and I recall that I answered in a fashion "wasn't this obvious then" ? But all I did was adjusting one of the posts in there saying "I have moved this from ..." and plainly forgot to tell similar in here.

Good that you did this.
Peter

Thanks Peter.

Cheers,

Nick.

[Leo]

Just in time before Peter probably will replace the Dexa clocks with a new Q parameter , I would like to tell about my experience with implementing these superdanes. With the online help of Nick (thanks!!!) I got them in quickly and what to say. The sound is just so pure and wonderfull and it is almost impossible to leave the room for the rest of my tasks and duties and pleasures (you just never know when she is reading this stuff...).
I also played around with the settings that Nick suggested which seem to work in the same direction (but I have been up placebo-creek before...).
And whether this is related or not I can now play with the SFS of 0,8 which gave massive hickups in the sounds and large amounds of errors in the XX control panel. This SFS change I tried after the first two days of Dexa glory. And this also moved the SQ further in this same natural, real, exciting direction.
Maybe the lower speed of RAM (800) I had before in my previous settings is a factor in this SFS thing  as well.
Allthough expensive and with the risk that Peter will get the same step, no jump, in quality  with a future release of XXHighend in the near future I am enjoying the great sound I am having today enormously.
Onwards and upwards, what a great journey!

Leo

[Nick]

Leo hi,

Im so pleased that you have had such enjoyable results. They really are quite something. Even after a long period of time the sound still raises a  smile.

Kind regards.

Nick.

[Nick]

Hi,

I just wanted to close out this thread with a report of the best outcome.

The breakthrough noise that is described at the start of this thread is gone.

 

My system will now play at XX software volume control settings of -144 db and is silent (no distorted faint music plays anymore).

The fix for this long standing problem ? The NOS1a upgrade.

I've posted elsewhere about the musical magic of the NOS1a, in addition to this magic it's the fix for the breakthrough problem as well. I suspect this may not be by chance :-). That's one of the nice things about NOS1 ownership, Peter is just so determined to do things absolutely right. Very nice in a world where development of much equipment is influenced by bottom line return and not a pure focus on sound quality.

Many thanks Peter.

Kind regards,

Nick.

[PeterSt]

Thank you Nick. So nice to hear ...

Peter