Your right Peter you posted whilst I was drafting. I think we have similar ideas. Wouldn't it be nice to have access to USB analyser just to know one way or the other.

Great that your link could be up by Monday. I think ill back off on my build and see what you make of it first. Fingers crossed for a good result ! Do let us know 

Regards,

Nick.

Peter hi,


The Paul Pang card has a TXCO and the Dexa is temp controlled (not oven but 37 deg constant). The Spec that Dexa quote for stability is 0.2ppm which is OCXO territory so I think there is a good chance that Paul can get close enough. I'm just suggesting that Paul gives it a go just to see what happens.

My context for this is that the last time I was doing this with clocks was back in about 2008/9 with a £52 pound M-Audio transit interface with an Audiocom Superclock 4 fitted (not in the same class IMHO as the dexa and the NOS) and the results were very good and repeatable when tuning the M-Audio clock against a stock PCI USB 2 card with a standard Xtal fitted. I don't think we need to be too hung up on precise cock speed matching, just tune my ear, believe me you know when you reach the sweet spot 

Some nostalgia

http://www.phasure.com/index.php?topic=979.msg12931#msg12931

I agree the Dexs the costs is a bummer but the based on subjective listening its just the best clock that I'v listened to to date, and MUCH easier to apply consistently without ground loop problems than direct coupled clocks (these have been a problem for me in the past) which is convenient for DIY. I don't know what the Phase Noise Spec is but they do sound very good. I'm not suggesting that anyone else uses them, they work well but you might have to be a little mad to have the three that I have in my system

I am with you about the intermodulation of the two clocks being a possible problem. I lost a post earlier (dammed ipad battery) about the clock speed and thoughts on possible effects of the clocks on data and SQ. In essence i'm not really seeing this as an electrical noise issue. My money is on data transmission error rates being vastly improved and if USB "bulk transfer" mode is being used to transfer data then the reduced error rate will reduce the number CRC errors and so the number of "Stalls" and retransmissions on the link. Of course this assumes that the stalls disrupt data processing further down stream but this seems possible. I think the USB receive buffers on the NOS USB chip may also have a role in the effect of clock speed mismatch in that tuning the relative speed of the clocks might mean that there is less data transmission speed management needed between the ends of the USB link. The event above only have to happen at audio frequencies and its not a big jump to think that this is going to be audible.

All theory, I guess the only way to prove this would be with a 480Mhz USB analyser to watch the USB Protocol error rate and frequency of dataflow management packets to see if they change with better clocks and lock speed matching. But such analysers are big bucks and really whilst I would love to know what is happening the resulting sound may have to be enough.

My thoughts at the moment on clock speed are that if clocks running at the same speed (slaved) turns out to be the best set up, then this will have a very nice simple elegance to it. I think this might well be the best solution but part of me is still thinking that, taking the USB receive buffering into account, it might be that a slightly faster NOS clock could be the sweet point. As mentioned above I'v ordered some test equipment to try to pin what the best solution is. Meanwhile the slaved clock build continues just to see what happens 

Regards,

Nick.

Paul hi,

Do give it a go, it's the trim pot next to the xtal can on the dexa. It's a variable cap with one full turn of adjustment. If the speeds are out it could REALLY make you smile (the 5.1 type sound stage is back again here  )and it takes moments to adjust.

Cheers,

Nick.

Paul hi,

Just to clarify, that is what I'm suggesting above, use the dexa trim pot. This is the set up I had years ago with the m-audio card and audiocom clock. You will just be setting the best sounding frequency on the dexa relative to the Paul pang card.  I could make a big difference. Listen for the sound stage expanding whilst keeping good dynamics and no sharpness.

There are a number of ways of thinking about the effect of relative clock speed. I won't go into the details but equal speed clocks (or slaved) may not be the best setting. There could very well be an optimum difference in speed that suits the data transmision rate and the buffer size at the reciving end.

I think its imporant to understand the relationship so i have equipment on order to test explicitly these theories. Will post back with results, then we will know of the trouble of transmitting a clock 1.5m whilst maintaining clock performance is worth the effort.

Cheers,

Nick.

Its a cruel drug not to have  once tried

The heavenly trimmer  could still work with the paul pang card. Just remember where it was set in case it needs to go back. It might be an interesting result.

Best Nick

First feedback,

Trimming the speed of pc end usb clock.

I was speaking to Paul earlier about the slave clock setup. This reminded me that the sound characteristics I have here now are similar in some respects to a modified m-audio transit card I had years ago (there is a post about the set up on one of the boards). The recognisable sound between the two system arose from trimming the clock speed on the m-audio transit interface (it had an audiocom superclock 4 fitted to the usb interface).

5 min and the trim pot on the dexa clock of my pc usb card clock was trimmed by ear and the same control over sound emerged. One adjustment extreme gives emphasised sharp edge and slightly splashy sound the other super super smoooooooth and clear detailed sound. In between comes a double sized sound stage pure pure detail ultra real just there in front of you sound. Exactly like the m-audio sound but sooooo much better !!!!

The trim pot is hence forth to be know and the "heavenly trimmer", haha.

I love this sound !

Slave (single) usb clock results to follow. Its going to be interesting to see if a set difference in clock speed is better or worse than the same clock speed at both ends of the usb link.

Nick,

Ps variations between systems / usb cards might be in part down to luck of what the relative speed of usb clocks at each end of the link happen to be........ there is a thought. ...

Peter,
I just re-read your post I think now you may mean something other than clock slaving ?

Regards,

Nick.

Our posts crossed Peter. Im on it 

Coen hi,

When I mentioned the "issues" that still have a possible effect sound quality (above), relative clock speed is one of them. It might even go so far as one end of the link being better running slightly faster or slower than the other. This might point to PPL sync / recive buffering being a factor.

Slaving both end is one of the things I am trying amongst a couple of other approaches.

The only way to fine out is to give it a try  

Regards,

Nick.

Coen, All,

I was in correspondence with dexa some time ago to ask if they could supply 24mhz. I mentioned that there may be a few orders to follow  

Having used other clocks previously currently the neutron star is my favourite clock type right now hence the selection despite its price. This is due to its transformer decoupling and subjective performance. The dexa nutrino looks good also. Either should be straight forward to apply.

Be aware that there are still some small factors that need further understanding regarding the two clock set up which might lead to slight sound quality issues. I am thinking about how to address these which may change the implementation and i'll post with an approach if I can solve them.

To obtain the balanced sound quality improvement from the clocks, my view is that the mods to the usb board that I posted about in the hunting for noise thread will be needed which Paul has applied.
I had not really wanted to encourage people to go down the clock and interface modification route due to the risk of damaging a NOS1 and the  issues that this could cause for Peter. For those who intend to go ahead anyway, I would be happy to provide the advice and guidance provided to Paul on how to implement.

Regards.

Nick.

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.

Hi

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.

Hi,

Iv been trying the Q5 setting this week. In terms of sound quality I agree with what has been said above, there is a beautifully analogue presentation without harshness and edge. Here I do also find that there is a slight drop in pace and drive in the music (I feel the need to use a more forward set of interconnects than the ones usually used to compensate). It might be that I am getting used to the new Q5 setting but I think that transients do not have quite the same weight which results in a slight loss of presence and engagement with the sound. Overall though its a big step forwards.

What has been fascinating is that I have the feeling I have heard almost the same change in sound characteristics before. I think the change is very similar in character to that experienced from changing the 24mhz USB clocks and applying bypassing caps on the NOS1 USB board.

Regards,

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.

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.