Could you, perhaps, elaborate some more on all of this?

I'm sure it seems very straightforward to you, but I'm still unclear as to what you are trying to describe to us.

Thus far, it sounds like you only ever hear static from your empeg, regardless of the audio source chosen (MP3, AUX, FM, AM). Right?

In which case, something's gone awry with the DSP mixer in the empeg itself. I don't see this having anything to do with the tuner.

Cheers