Amp "backfeeding" head unit shuts off all speaker outs

[reapher]

Hello to everyone here!

I have a 2001 blazer w/ stock delco stereo w/o amp, and recently got an old amp(crutchfield 50x4 performance series, in 100x2 mode for sub) and (2x10" black phantom(cheapo shit??))sub box from a friend, I just don't have a great head unit yet so no pre-amp outs yet //content.invisioncic.com/y282845/emoticons/frown.gif.a3531fa0534503350665a1e957861287.gif Admittedly I don't know much about hooking stuff up other than RCA jacks //content.invisioncic.com/y282845/emoticons/rolleyes.gif.c1fef805e9d1464d377451cd5bc18bfb.gif I managed to get my amp and sub in the back of my blazer wired spliced into rear speakers and powered, fused, grounded, 200hz low pass filters on the way so I'd like to get this working properly! I'll have to wire the amp power control to a fuse that's only hot key on-engine on(??) but I got it working anyway.

The problem is that I lowered the gain so the amp would take speaker level ins and wouldn't have to fade all front, and since then I've been getting the problem of after a minute or so of playing music all the speakers go off, stereo still running afaik but when I turn the key off after this happens I can hear a "discharge" sounds like it's coming from the head unit or speakers. A friend told me that the amp is "backfeeding" or overloading the head unit and it's shutting itself off. This only happens when the spliced RCA cables from rear door speakers are attached to the amp in, whether or not it has power.

What could be my problem? Is it something to do with the gain? I'd say it was about 10% up to take speaker level. What is the function of the speaker return wire? If this is overloading the head unit or whatever, could I ground these to the body with the amp so the head unit is not affected? I really dont know what's going on, I plan to get a new head unit but I'd like to see if I can get this working in the mean time

Thanks for your time and responses!

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[reapher]

This actually happens at any gain level but after a minute or so all the speakers shut off and when in CD mode it will say "ERR" and then make a discharge sound when I turn the key off, any time the amp ins are spliced into the door speakers with or without power to the amp.

What would cause something like that to happen? The 12v right from the battery runs under the carpet near the spliced RCA cables and they are a fairly thin wire idk if that has anything to do with it? It's like the head unit is building up voltage, amperage idk like a capacitor and discharging when it powers off

I am def getting a new head unit though since I got $600 debt for the car payments removed thanks to birthday gift from dealer //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

So I have an amp and subs, FMODs being delivered but they may become unnecessary w/ good head unit. Need a new head unit with pre-outs and pref USB/MP3 front input and a new set of front speakers. Could I get this done w/ new equipment for around $200?