$500 USB cable

Jim Aud of Purist Audio Design

When thinking about a digital signal over USB, it can seem natural to think of it as a straightforward expression of 1's and 0's. However, it is more nuanced than that. Below a certain voltage, the signal says: "this is a 0." Above a certain voltage, it says "this is a 1." So, a 1 may be a 3.2 volt signal, and a 0 might be a 2.9. Since data transfer happens fast and often, it doesn't take much to skew a 1 to a 0, or a 0 to a 1. The digital signal isn't this series of neatly packaged squares, all labeled 1 or 0. They are in the ballpark, but they aren't completely uniform.

Any opinions on these statements from Jim Aud - Purist Audio Design ? 




  

Very informative post Al. Thanks.
Trying to better understand what you are saying in a couple of areas.
   
When you say USB communicates data via a differential pair of signals, and specifically regarding noise.

And noise that is present on both signals (i.e., common mode noise) will be ignored under any reasonable circumstances, when that determination is made.

I don’t doubt that USB cables can make a difference in many applications, mainly as a result of coupling or radiation of noise into D/A converter circuitry or even analog circuitry further downstream.

So do you mean that noise can be introduced into D/A circuits, only by un-reasonable (not normal?) circumstances?

If yes, can you give examples of this ?

thanks Chris

Thanks Al

Have heard/read the "0 - 1" process explained numerous times, but not as good as you did. Interesting what one can read in the audio online glossies. The article that statement came from was only a year old.

I did a lot of research before I bought the DAC I use. As an old school computer guy, the fact that it advertised USB design, with performance that equalled S/PDIF was a big selling feature to me. It has lived up to its claim.

Been part of the IT industry my whole adult life. Still remember using the IBM 360-370, Amdahl, Tandem etc... mainframes and all those reel tapes. :^)

Cheers Chris