Hello,
I have a USB audio interface (3D Sound Audio Interface see below) plugged into a raspberry pi. When I have it selected for audio input (port audio seems to be the only one that works) along with audio output via the speaker on the GPIO pins I get crackling as if PD can't handle the processing of audio input while outputting on raspberry pi. NOTE: if I turn off audio input the output sounds perfect.

Anyone else encounter this issue?

FYI, I hooked up a nice little speaker to make the Raspberry Pi more portable via the I2S Amp on connected and powered by the GPIO pins (see this link for details