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In Reply to: RE: Cable effects same regardless of USB mode posted by Tony Lauck on November 30, 2009 at 13:33:30
The problem is ground noise coupling between boards (or "independant" sections on the same board). It is possible to setup the grounding schemes to minimize this, albeit not very easy. The easiest way to get around this is to use non electrical connections between sections such as optical, but these generate their own jitter.
I tried this a couple years ago with three boards running completely separate power supplies with grounding schemes designed to minimize ground coupling between boards BUT things like the length of the USB cable STILL affected the sound! It was true that the resulting sound was extremely good, but maybe because of that the USB input differences seemed even greater.
BTW this was a very expensive DAC to make it was close to $3K just in parts, not counting the case with multiple separate shielded compartments etc. Something is still leaking through even when we do our best to stomp it out. I've come to the conclusion that we still don't really know the root cause. The stuff I talked about was stuff we know about, but there has got to be something else going on.
John S.
Follow Ups:
nt
In general short cables sound better than long cables. Thats not an absolute, its possible to have a 4ft very good cable sound better than a cheap 3ft cable, but that cheap 3ft cable is probably going to sound better than any 15ft cable.
I once tried a 20ft cable (which is longer than the spec allows) and it sounded terrible.
The short is best does not hold true when you go to optical cables. In my setup the 30ft Optics cable, with the device driven by a good linear supply, and a short cable from the optical end to the DAC sounded better than any regular cable.
I even had good results with active extension cables with a short cable from the end of the active cable. Others have had very different results with this setup though.
John S.
I'm going to try 0 cable length on the Musiland 01US by soldering a Male A USB connector to a Male B USB connector - this should allow minimal length. If it proves better than a cable I'll put a male A connector on the pcb for an even shorter & more robust connection - just like the M2Tech HiFace!
Edits: 12/02/09
I have gone through a similar series of upgrades on my reclocker. My initial expectation was that the input cable would have not effect. Well it did. Then I discovered that I had to isolate the power, the ground and the input timing from the output circuits.
Shame you didn't check this out before putting the PaceCar on the market and letting customers (like me) find out that it didn't stand up to the claims being made of it.
I have said this many times here. One often need to find out the hard way, and then not trust reviews or vendor claims.
Yep, no argument there.
Thank you as well, Steve.
Thanks for your insightful, intuitively sharp posts, John. Much appreciated.
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