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Wish I had a clue why - I can't think of any reason why being connected to 2 different amps (or connected by another set of RCA's) should have any impact....

d-

Have you tryed 1 set of RCAs with a Y to run to each off a single line out?

Not yet since I want to diagnose the underlying issue - I am completely positive that that will work, but I'm also positive I will lose my fader control :)

Y-cables it is until I can solve the issue!

d-

ok so you want 6 channels, and have only 4 channels out from the head unit.
my suggestion is that you pick up a Coustic XM-3 or similar electronic crossover.
it allows for F?R-L/R inputs, and gives you an additional pair of sub outputs, with full range of control for crossover points, and attenuation.
that's what you really want to be using in this situation

Hi Glasswolf,

I am trying to power 4 sets of components and a pair of subs. The 504 provides 50watts to each of the components and the 3002 provides 300 to each sub.

I have an electronic MTX crossover I could use, but I have crossovers built into the amps and therefore didn't leave a space in which to mount it. I probably could make room for it, but I don't really want to redo my setup since I just got it finished :) If I can't resolve this I'll be finding a space for it, trust me!

Having said all that, as I was troubleshooting again yesterday, I accidentally hooked up the RCA's to the sub amp while the power was hooked up but the ground and remote turn on were not. The power light turned on very dimly, which obviously means there is some direct connect to ground through the pass through rca's. I'm assuming this is not normal, but can you please confirm? Interestingly when I hooked up the RCA's from the head unit (I know, I shouldn't have, but I needed to troubleshoot) the amp did not ground through them, so now I'm thinking the issue is with the 504 passthrough circuit. Thoughts?

Thanks in advance - I appreciate you continuing to provide advice and help!

One last question - can you recommend an amp repair place that might still be capable of refurb'ing old MTX amps? I figure it can't hurt to have them generally checked out...

Doug

As an update, I installed a Ground Loop Isolator between the 2 amps. Since this resolved the issue, I'm guessing there must have been some type of feedback getting into the RCA's between the 2 amps.

d-

As an update, I installed a Ground Loop Isolator between the 2 amps. Since this resolved the issue, I'm guessing there must have been some type of feedback getting into the RCA's between the 2 amps.

d-

actually in unbalanced RCA lines, the outer part is a ground. the inner center pin is the positive/signal

Hi GlassWolf -

At least in theory the BMW outputs are supposed to be balanced RCA's, and I did notice that when I disconnected the negative leads that my signal got significantly quieter...

d-