KJ, if mute doesn't stop the noise, it has to be from that point on. Check each connection, and try cable substitutions. If the bridging is switch-selected, try (with the amp OFF!) flipping the switch back and forth a few times to clean the switch contacts.

Another thing to try is see if the noise happens with the amps' inputs disconnected, and with the input shorted. Also, one step at a time, swap a working channel or component or cable to the channel with the problem, to eliminate one thing at a time.

The last thing to check is the speaker itself, which includes the internal crossover components. To do this, temporarily swap speakers and see if the same speaker or another one makes the noise.

The idea is to narrow down the problem by seeing when you can make the noise move to another channel or speaker, thus pinpointing the noise source.

Larry
www.fineelectricco.com