I had the same issues with a BAT preamp. Bad output capacitor...not sure if this is what's happending to you. same symptoms.
Popping when source is switched or muted HUH????
What might be causing this? I am using a Rotel Pro, it is running through a cheap monster 2000 powercond. I am using Innersound EROS MKII active crossover vertical bi-amp, I get this popping sound in every mode switch, using mute, cable channel changes, even on digital bypass (muti channel) internal bypass of everything except volume, so it is either electrical or in the processor...please any ideas? thanks Chad