Stereo popping noises

Okay, after I replaced the entire sound system in my buick with a 12-speaker amazingly awesome sound system I designed myself, I took the original delco stereo and wired it up into a box to drive the sound system on my PC (Another self-designed system...) Problem is that it developed a popping noise every time I turn it on/off, press the "loud" button, or change stations on the radio itself. The problem started after repairing a incessant buzzing that was solved by grounding the stereo chassis to the pc chassis. No clue why it has a ground loop problem to begin with, no wires crossing anywhere they shouldn't, and all wires are sheilded inside the computer and the stereo enclosure.

I know that the popping is resulting from the amp, but how do I eliminate it? It bugs the crap out of me, and makes my sub enclosure (which doubles as my chair) wiggle.

some amps pop if you have a low ohm load on them

I took the stock speakers (I am NOT a packrat...) and hooked them up and it still pops. Stock speakers have 12 ohms or something like that whereas the speakers I'm driving are all 4 ohm.

Then I opened the stereo, and on the amp there were a buncha leaking and blown caps. I replaced all the amp caps, and one other cap on the tuner board and....

it still pops when changing stations, turning the "loud" feature on, and turning on/off the stereo.

I guess my next question is where is the relay that switches the amp on/off? At this point all the caps are not leaking so other than a relay I don't know of any other "source" that could cause the popping.

the popping is usually a ground problem. If you want to find where the auto turn-on stuff is, folow the wire/lead on the circuit board. The one in the deck is probably a small tranisistor rather than a relay.

I've located a "switching" voltage going into the amp from the control pcb. With the amp on, it shows 2.15v, and 30mv when the amp is off; however this doesn't change when pressing the "Loud" button. It appears as if the 2.15v signal goes into the amp chips, the signal from the loud button comes directly out of an IC marked Delco 205 and is grounded to activate the loud function. It appears as if this chip is controlling the input to the amp chips. The amp pcb doesn't have any transistors on it, only caps and ICs and a single pot. My dmm isn't picking up any spikes in voltage (but has a 2Hz refresh rate on the screen so it may just not show it).

I am assuming all of this is in the headunit. The loudness button is basically one of two things, either a fixed value EQ or and EQ that varies boost with input signal. Either of these functions could be accomlished by an IC. If I understand it right, the signal should go into the IC, be EQ'ed then go to the main amp chip. Have you tried different grounding schemes ? This is a typical problem when powering sound boards in a car stereo shop with a DC power supply. Try powering the car audio stuff with a car battery to see what happens.