Whenever I turn the car on/off with the stereo on, the stock subwoofer gives a small pop... Whenever I turn the stereo on/off, the subs I put in give a huge sonic boom kind of pop...definitely sounds harmful. Any particular reason why? Could it be because my remote wire isn't really on the remote for the stereo (just a 12V wire from the fuse box that goes live when the ignition is on).

Also, I'm getting a lot of engine noise in the system...ran the power wire along the driver side and pulled the audio off of the signal line to the stock amp...so I don't think the signal wires are being tainted by the power. Ground wire for the amp is good...already tested the voltage on it. Any ideas?

 

For the popping sound....check that the amp is actually turning on and off. If it is, you may need use of a relay on the remote line.

For the whining sound, where did you run your RCA cables, and what BRAND and MODEL were they? If your ground is good, RCA cables are the next thing to check.

 

Yeah, the amp definitely turns on/off...but not with the radio, since it's not a remote wire.

As I said above, I didn't run any RCA wires. I tapped into the stock amp's signal and ran a wire back.

 

Ahhh....so hook up the amp to turn on and off with the radio

 

Can't do that...the remote power wire doesn't have enough juice to kick on the relay inside the amp...even with the stock amp unplugged.

 

Also use shielded cables ANYTIME you tap into line level signal wires. These are high impedance, low level lines that are very suspectable to picking up engine noise and crosstalk, etc. When tapping into SPEAKER level wires DO NOT use shielded cables, USE A TWISTED PAIR of wires. This is a low impedance, high level signal that is not very suseptable to picking up engine noise and crosstalk, etc.

An amplifier speaker line output does NOT want to see the added capacitance of a shielded cable. It causes a phase shift to the perceived impedance of the load as seen by the final output stage of the amplifier. This phase/impedance swing can cause the gain/phase margin of the final amp to fall below its safe design parameters and self destruct. A professional amplifier would have a gain/phase margin of 45 degrees. Some cheaper amps only design a gain/phase margin of 30 degrees into their output circuitry. When the margin falls below 15 degrees it can become very unstable. Depending upon the unity gain cutoff frequency of the amp, the negative feedback loop actually becomes a positive feedback loop which causes the amplifier to self oscillate and self destruct...

SO, as proper engineering practice, DON'T use shielded cables on speaker line outputs. This is ESPECIALLY important the longer the run is. But, DO USE shielded cable on line level wiring runs.
Make sense?

I know, I know... I was going to limit my responses to one paragraph How about one page?

 

As StreetEffectz sezs... If you don't have enough juice (voltage) left on your remote line to turn on and off the add-on amp, then your only choice would be to use an additional relay.

Not knowing what kind of circuit (open collector transistor or relay) that the stock head unit remote uses, I wouldn't simply add a larger wire to feed directly back to the new amp. I would install an easy to get 12VOLT 30amp automotive relay. Use the stock radio remote to turn the coil of this relay on and off. Run some "BEEFY" gauge wire back to your new amp remote turn on/off circuit from the contacts of this added relay and you should be fine.