Computer Audio Asylum

Music servers and other computer based digital audio technologies.

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RE: How can USB performance impact audio quality?

Posted by Tony Lauck on June 12, 2011 at 13:26:02:
The noise rides along with the bits on the USB cable and the circuitry in the DAC doesn't do an adequate job of cleaning this off. The noise can ride on the signal wires in the form of amplitude and phase variations or it can travel as common mode noise. In addition, even if logic circuitry receiving the USB signal completely cleans the signal this receiver circuitry creates its own digital noise which may couple through proximity, power or ground into downstream analog circuitry (which includes the clock running the DAC). As if that's not enough, the noise can couple out power wiring into downstream amplifiers.

None of this is logically necessary in the sense that some amount of noise is logically necessary with an analog tape machine, but it's still there. More effort has been spent on marketing hype than on the necessary hard core mixed signal engineering.

Of course, I've only listed the "known unknowns". It may be that there are "unknown unknowns" as well. The problem is tough because people can hear things that aren't easily measured, but they don't hear them consistently and so listening isn't by itself sufficient to solve the problem once and for all.