DaveR wrote:
I'm not assuming your first two points.
This is a fact: USB data is self clocking. Every bit of data contains the clock required to clock it into the receiving buffer. The USB clock does not have to be terribly accurate or precise by design.
Because of that fact, USB clock synchronization does work perfectly. USB did not invent Manchester coding, it's just taking advantage of it.
Gordon Rankin, who basically invented asynchronous USB, claims there are other sources of jitter, and that implementation makes a difference.
Asynchronous USB data transfer however doesn’t automatically guarantee perfect sound. J. Gordon Ranking informed me of the following: “Many of the less expensive units do not use a fixed oscillator and instead use a frequency synthesizer and therefore have worse jitter than a dedicated fixed oscillator. Many companies don’t even know how to power fixed oscillators. If you go to say Crystek and ask for a really good oscillator and then power it with a 3 terminal regulator the results will be less than staggering. For high end you need a discrete regulator with ultra low noise to establish a really good low jitter Master Clock.”Scroll through the product peddling in this article to read some of his comments:
http://www.digitalaudioreview.net/2016/ ... ty-varies/