How to remove engine noise from my subwoofer

[sewlow]

What size of ground wire for the amp are you using? It should be as large or larger than the power wire.
I like to run the ground from my amps straight back to the battery. That way, there's no second guessing the integrity of the circuit.

 

[twithers]

The ground wire to the amp is thick, but not nearly as thick as the power wire. I have one of those Monster cables that are about as thick as your thumb.

I thought that if I disconnected the rca's from the HU and the noise stopped, that would rule out the rca's, and everything with the amp. Leaving only the HU itself and it's wiring.

Is that not accurate?

 

[df2x4]

Possibly, but not necessarily. I've seen some amps that will sort of self-mute if no input signal is detected. Not sure if anyone still does this, as far as I can recall it was some sort of gimmick to lower noise floors and boost S/N ratios with performance equipment back in the day.

I'd say you're on the right track, but like Al said I'd make sure you're running the same size ground wire as the power wire on that amp. (And do what I said and ground it properly!) My gut says it's probably something with the head unit.

 

[michael hurd]

http://www.walmart.com/ip/Scosche-ES034-GROUND-LOOP-ISOLATOR/896355

Several companies make ground loop isolators.

Some amplifiers have very poor feedback schemes, I first saw this back when I was 18-19 with an inexpensive JBL amp. With the gain turned up too high it would cause issues. Adding a ground loop isolator healed the issue.

Of note, I had tried a small Soundstream amplifier in the same truck that had issues with the JBL subwoofer amp, and no issue.

 

[df2x4]

Interesting, I've used ground loop isolators before but only to correct distortion on an input source due to dirty (cheap AC inverter) power. Never thought of trying one before an amp...

If that does work it would bug the hell out of me, I'd be replacing that amp.

 

[21Actual]

I agree with the general consensus of poor grounding, or a fault in the head unit. If that all checks out and your at a loss, consider the use of some ferrite cores on the power to the amp, and the RCA cables.

 

[dannymcd]

Like everyone else I'd start with the grounds, I'd also try moving your RCA cables if they run right next to the positive cable, if there's poor shielding in the RCA cable it will all distortion from the cars electrical system. the ground loop isolators add an additional ground protection to the shielding of the rca cable, further protecting the signal from distortion, these come in handy if your pre-amp signal is 2-3v vs 5v.