My friend has a very similar setup to mine in his car and I offered to try and help troubleshoot his recent problem. It is kinda crazy cause when he turns the gain up on his 2 channel amp (which goes to the components) it causes the subwoofer to decrease in volume dramatically and vice versa. They are on separate RCA cables running from an Alpine CDA-9886. Running the amps individually they both run normally and the gains can be set normally. I also changed out his headunit with another one to check if it was something funky the head unit was doing but the problem is still there.
I guess my question is what could possibly cause the gain on one amp to reduce the volume of the other amp?
seems as if the current graw of the 2 channel is somehow drawing enough current to dramitically curve the output of the sub amp, post voltage readings of sub amp(at power terminals) before and after changing gain on 2 channel. long shot but wtf?