The PM-10's INPUT 1 and INPUT 2 jacks sum any stereo input to mono. However an audio device's balanced TRS (tip-ring-sleeve) output is not a stereo signal but a balanced mono signal. Here's the difference:
When connecting a balanced mono output jack to a stereo input jack that sums, the result will be that the balanced mono audio signal is cancelled out--the tip-positive and the ring-negative sum together.
There are two options to resolve this:
- Use a TS unbalanced cable instead of TRS.
- If the audio device has a headphone output, use a TRS cable to connect this jack to INPUT 1 or 2 of the PM-10.