Originally Posted by SlashtaCross
The pulsing stops when I flip the switch on the amp that says "subsonic". When it's off the speakers pulsate slowly and when it's on they stop. Someone pointed out that my RCAs are incorrectly installed. Both on the amp and on the receiver. On the amp they should be wired to the LINE IN instead of LINE OUT and as for the receiver end I have been told to get a "1 RCA male to 2 RCA female y splitter adapter" and run my RCAs into 1 sub preout. I ran my subs directly to the receiver and they're still working thankfully. The question is could I have damaged my receiver by plugging in the rcas to both sub pre outs? Could I have messed up my amp with the rcas running from line out instead of line in?
Being hooked to line out instead of line in on the car amp would definitely be a problem, sorry I didn't notice it. As for 2 RCAs to both sub-outs vs 1 and a Y-splitter, there's absolutely no difference... this is old advice from back when most AVRs had a single sub-out and sometimes on mono sub-amps with stereo inputs, hooking one RCA to a single input might not have a high enough voltage to trigger the amp's auto-on circuitry. On modern lower-end receivers with dual sub pre-outs, it's just splitting the same signal, so a single cable with Y-splitter is pretty much doing the same thing electronically.
Is it possible that running the RCAs wrong messes something up? Possibly, but highly unlikely, especially on the AVR. If you have a 3.5mm to RCA adapter laying around, maybe try connecting a pair of headphones to the sub-outs, raise the AVR's crossover to 200hz, and see if you hear anything in the headphones with music playing, that should confirm the sub-out is fine. If it is, then hooking the same 3.5mm-to-RCA adapter to the line-in inputs on the car amp with a source (like your phone if it has a headphone jack) and listening for playback should then narrow it down to the car amp or power supply.
The fact that the subsonic filter eliminates the pulsing seems to point some low-frequency harmonic, possibly from the power supply failing or possibly from the amp. Now that the input cables are correct, are you getting playback with or without the subsonic filter on? Getting an exchange for the power supply from Amazon should be easy enough, so if replacing that doesn't fix it, the car amp probably kicked the bucket... at which point, just return the power supply for a refund and source a plate-amp or pro-audio amp.