My Pittsburgh Outs arrived today and I did a BUNCH of tests on various power supplies and different ways of routing signal and I could not get the digital noise.
Although both yours and mine have REV7 written on the board there are at least 3 resistors that are not populated on yours but populated on mine and at least another 3 resistors with completely different values between your board and my board.
Also notice that your OUTS uses A50k pots (i.e. log pots) and my OUTS uses B50k pots (i.e. linear pots). So it could be that all the differences in the resistors are just due to the need to add tapering resistors to the linear pots to get a log response (which is the typical curve used for audio volume).
So results are inconclusive. Need more data.