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 61 
 on: July 20, 2014, 05:52:05 pm 
Started by manisandher - Last post by manisandher
My guess: With your new set up, there is a narrow cancellation somewhere between 60 and 100 Hz.

There may be, but I think the slight increase in LF output via DSP has already fixed the issue. The boogie factor is now there in spades.

Hi Mani, it could be that all your life we have been used to hear distorted bass...

I think you're right Alain - what I'm probably missing is the harmonic distortion low down that I'm so used to. Perhaps I should bypass the internal amps and use an external tube amp... OR just get used to accurate bass reproduction... haha.

Mani.

 62 
 on: July 20, 2014, 05:45:58 pm 
Started by manisandher - Last post by manisandher
FWIW ... Personally I would never take headphones for a reference; They are too different.


Otherwise headphones and speakers (with the influence of the listening room) are two different worlds.

Thanks for your thoughts guys.

Of course, listening through headphones (or more accurately 'head speakers', in the case of the K-1000s), could never be mistaken for the real thing, whilst with (the very best) speakers it could. But when I talked about the 'sound' of my AKG K-1000 headphones in my previous post, I really meant 'tone'. There is a 'colour', a 'liquidity' to the tone with the K-1000s that I find simply intoxicating... And I'd love to have it in my speakers.

Sorry for causing the misunderstanding.

Mani.

 63 
 on: July 20, 2014, 03:34:57 pm 
Started by PeterSt - Last post by manisandher
Thanks Peter.

Here's something that John Swenson wrote on CA:

"First off, USB is not one signaling standard, there are currently 3 in use, the one in use for a large percentage of DACs at the moment is the high speed standard, so I will cover just that.

HS mode runs at 480 Mbs, at this speed over normal human cable runs(measured in meters not mm) the "signal integrity" (SI) at the receiver can vary GREATLY. The spec allows for a very wide range of SI at the receiver, this means the receiver circuit has to be good enough to recover the data over this wide range of SI.

This receiver is NOT just a simple logic gate input. It uses a multiphase clock at 480MHz, some use 8, some 9 and the ones I worked with use 12 phases. This means there are twelve clocks, each at 480MHz, but slight delays between clocks. These different phases are generated by digitally controlled delay lines with 1/2ps resolution, you read that right, one half pico second resolution. Each of these clocks controls a very fast ADC with a few bits resolution. Thus every "bit" on the incoming analog signal is sampled 12 times, the digital representation of these analog values go into some DSP circuitry that tries and figure out where the "edge" actually is amongst all the noise, jitter and reflections on the wire.

If the SI is pretty good this determination is pretty easy, if the SI is not good, it has to work harder to figure out where the edge is. Part of this process is continuously tweaking the frequency of the clocks AND adjusting the exact delays of each of those phases to get the best data to the DSP block. Even though the clocks are 480MHz, the rate at which the frequency and delays are adjusted is right in the middle of the audio range. The worse the SI the more tweaking goes on.

Lest someone thinks this is USB only, this sort of thing is the basis for ALL high speed serial interfaces. USB HS is actually the simplest because it has to be dirt cheap, others do even more complex feedback on the input parameters. You really don't want to know what goes on in a thunderbolt receiver!

All of this processing to track the input signal generates lots of noise on the power traces and ground plane of a board. Even with very careful circuits and board layout some of this gets through to the DAC chip and its clock, which CAN change the output signal. Note: none of this actually changes the bits, that input circuit IS good enough to recover the actual bits. It is the consequences of the heroic measures taken by the receiver to get those bits in the face of poor SI that can affect the sound.

Measuring this stuff is not easy, frequencies are high and amplitudes are low. I don't have anywhere NEAR good enough test equipment at home to do this justice (we are talking about at least $50K, I can't afford that!!) and if I tried to use the stuff at work, I wouldn't be working, so a book full of graphs proving all this is not going to be coming from me anytime soon.

Gordon just got some equipment that CAN show this so sometime in the future you might be seeing some data from him.

I hope this helps a little bit in understanding how a USB cable may change the sound of a DAC.

John S."


I think the NOS1a has eliminated this as a cause for differences in SQ between different USB cables. But I'm posting this as a reminder of how complicated this all can be.

Mani.

 64 
 on: July 20, 2014, 12:55:04 pm 
Started by PeterSt - Last post by PeterSt
Thank you for your help and considerations Mani ...

Peter

 65 
 on: July 20, 2014, 12:51:58 pm 
Started by PeterSt - Last post by manisandher
And another point while I remember it...

I also tried the mobo USB port vs. the Silverstone card. The Silverstone card was much better than the mobo... but only with its bracket still attached.

So in summary, the best sound I achieved was this:

- SS card with its bracket attached (i.e. non-isolated)
- 5m 'standard' USB cable

Both these findings were total shocks for me and the exact opposite of what I expected (so no placebo here).

Oh and in case it matters, I have never touched the black cable within the NOS1(a) itself.

Mani.

 66 
 on: July 20, 2014, 12:43:57 pm 
Started by PeterSt - Last post by manisandher
... I was told a week or so back...

I came to the conclusion that USB cables now matter greatly (with the NOS1a) about 3 weeks ago. I wasn't even looking for differences but just stumbled upon them. I was experimenting with where I could place my PC and NOS1a, and had pretty much resigned myself to having them both sitting exactly between my speakers in my main room. I then decided that it would be better to have the PC in the corner of the room, which would require a 3m (or so) USB cable. I got out my (very) expensive 3.5m USB cable, plugged it it and immediately thought WTF?... this sounds way worse than the 'standard' 1m cable I had been using!

I then went through a bunch of USB cables (all cheap printer cables) of various lengths, and they all seemed to have a slightly different sound. Unfortunately, with the way things were situated, I couldn't try a 0.5m length - maybe Paul (Scroobius) can share his findings with short lengths when he tries one. But what I did try was a long 5m USB cable. And you know what? It sounded way better than any other cable I had tried. So with my setup, there isn't a clear inverse correlation between length and SQ. If I had to hypothesize, I'd say, generally, the shorter the USB cable, the better... BUT...

... Very long USB cables (getting to the edge of the USB spec) may sound even better. I know they are very different animals, but I've found exactly the same thing with spdif/AES3 cables. The longer (~5m) cables sound better than shorter ones. For these types of digital cables, the practice actually matches the theory - they are terminated (or should be) so RF reflections come into play. As for whether the same theory would apply to USB cables, I have no idea.

Oh and BTW, I get absolutely zero USB errors showing in the USB Control Panel with the 5m USB cable.

I think Peter's advice of trying a few 'standard' (i.e. non-audiophile, non-expensive) USB cables of different lengths is bang on. So my strong recommendation is to buy a bunch of 'standard' cables from 0.5m to 5m lengths and give them a go. I mean, why not? The outlay should be no more than 20 Euros max, right?

Mani.

 67 
 on: July 20, 2014, 12:35:06 pm 
Started by PeterSt - Last post by PeterSt
Hey Alain,

Paul can speak for himself, but it never was a subject. So we can also twist this into : we never asked Paul to let it stay or to remove it. So whatever it does or does not, it should not influence the upgrade itself.

Regards,
Peter

 68 
 on: July 20, 2014, 12:20:50 pm 
Started by PeterSt - Last post by AlainGr
Hi Paul,

You asked Peter not to remove the Dexa clock from the NOS1 while being upgraded to the NOS1a ?

Alain

 69 
 on: July 20, 2014, 10:10:19 am 
Started by PeterSt - Last post by Scroobius
Oh Dear I thought I was finished with tweaking. So maybe Dexa clocks on the USB interface will still make a difference? I removed the Dexa from the PC (while my NOS was being upgraded) so later today I will put it back and see what happens (the 24MHz USB Dexa remains in my NOS1a).

Also I still have my super short 25cm USB cable which for various reasons was removed but I shall put that back in today and report back with findings.

How can I explain to Ros that this is more important than gardening?

Paul

 70 
 on: July 20, 2014, 09:39:37 am 
Started by PeterSt - Last post by PeterSt
HA !
And why not. The middle switch is free ...

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