Over the weekend I had a friend borrow one of my mixers and reported back that the pre-amps were broke on almost all the channels. I was not aware the board had any issues, it's always sounded & performed well for what it is - an Allen Heath GL2400-24.
He determined it was broke by inserting a SM57 into each channel, turning the gain completely up and noticing a slight signal blip on LED on the neighboring channels.
When listening to the output - it sounds overloaded and crackling? (no shit)
In 'normal' use of the board, gain/trim right round 15-20/unity. I've never had to push it to max, on anything. When operating at in this range, the board sounds fine.
Is this a proper technique of 'testing' a console?