I’d be going back to that service guy and politely ask WTF??? It was working before he got it and doesn’t work fine when you got it back. Pretty damn simple math there, and I’d be right pissed off if I was you.
Weird crackling from speakers when preamp connected
I've got an MC275 hooked up to a VTL 2.5 preamp, when I reconnected it after some maintenance, whenever I turn the preamp on then the amp, once they both warm up, the crackling starts.
I hooked up the amp to my DAC and had no issues with crackling, swapped tubes, interconnects and power cord, different inputs/outputs, same crackling issue when using preamp but no issue when connected to the DAC as a preamp.
Sonus Faber Olymica !, MC275 Amp, VTL 2.5 preamp, Auralic Vega DAC, nordost interconnects/speaker cables, panamax power conditioner.
My last step is to see if I can either borrow a tube preamp or buy a cheap one to test it.
Any suggestions are welcome as I'm running out of ideas.