this is a big maybe since i am not a electrical expert...
since you have so much equipment running on a 4 guage, i think they might be struggling for power....does the power wire get really hot after its been running after a while?
from what i can remember those arent class D amps, A/B amps draw a lot of power. i have a 4gauge running my 600.4 and another 4 gauge that i used for my sub amp.
also, how is the amp positioned? make sure those fins on the amps are mounted correctly to get the best air flow...thats not the cause of the noise im thinking, but just something to check.
also is the amp rack made of metal? or is it touching the compressor or allowing the amp to ground out to the chassis?
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