Are all asynchronous USB inputs similar?

I would expect that different asynchronous USB interfaces will generally differ significantly in terms of how much noise and jitter (timing fluctuation) ends up being present on the clock (the timing signal) that is provided to the D/A converter chip itself. That in turn can be expected to have significant sonic consequences.

Even if the electrical designs of two asynchronous USB interfaces were identical (and in general they won't be), just differences in mechanical layout, signal routing, grounding, power distribution, etc., would be likely to result in significantly different amounts of jitter.

Regards,
-- Al

Al is correct. Each design is different. Its not just jitter either. The output driver impedance matching and voltage is critical too.

Steve N.
Empirical Audio

The one thing that they all have in common is the poor sound quality. USB is for connecting your printer, not your DAC. If you notice the new era of servers, they have abandoned USB due to its poor sound quality. It was originally used as people just did not want to open their computers, so, since USB is like a belly button (everybody has one), thats what they used. It was a convenience thing and never meant for high end applications. This just snow balled with the manufacturers (it was easy and CHEAP)as they all embraced the interface. You can now see how the new designs are not using USB due to a myriad of reasons, one being the natively horrible jitter factor. You need to spend alot of money just to (try) to tame USB jitter.