Amp problem: 10 of volume


I bi amp Aloia 150.I amps. I noticed a just audible crackling noise off and on for a day then hardly any sound at all. I checked all fuses and they tested good. I get sound but only about 10% of the volume compared to the other amp. After troubleshooting it is definitely the amp. Any ideas?
128x128snook2
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Not likely these are the fuses or output stage of the amp. Most likely it can be an input(driving) stage.
There can be (not sure if that's the case) shunting of an input driving stage and feeding the output stage with the small signal.
A professional tech can trace this problem pretty quickly.