post #646 of 646
I just updated the PPA website at with a small section on wiring considerations:

Signal ground is input ground, not output ground. Output ground is the output of the ground channel. It exists solely to drive headphones. It is not a true ground. Do not connect signal ground to output ground. This defeats the purpose of differential output and may cause amplifier instability. Do not use the headphone output as a line level output as this may short signal ground to output ground. Use signal ground instead of output ground for line level outputs.

Do not connect V+ or V- to the case. This may cause damage to the amp or other components.

Connect the case and pot housing to signal ground. This will shield the amp from hum and noise.

Do not connect AC ground to signal ground or the case. This may cause ground loop problems.