Just making sure I get it: you're suggesting using RPi #1 to try and capture the table's USB out with CamillaDSP, and routing that out of another one of that RPi's USB ports, and then using RPi #2 to see if it can "capture" the sound from RPi #1's output ? Or do you mean that within RPi #1 I could use stuff like REW to check whether I am successful in capturing the turntable's USB out and routing it out of the Pi ? Sorry I am at ease with tweaking around with the RPi but pretty new to audio stuff.You should be able to check it with something like REW or Audacity on the RPi. When I first started experimenting with this stuff I used REW to see if I could capture sound from my desired input device. If you can do that you are golden.