Longest USB cable length to DAC for audio?

[Speedskater]

As in any digital interconnect situation, as you lengthen the cable you get on a slippery slope with intermittent drop-outs and a little longer the interconnect stops working entirely.

But it's system dependent. output stage, cable model, cable length and input stage are all important.

And as with all digital interconnect systems, audio quality stays the same until the drop-outs cause error correction system problems.