Plea For Help: Engine Whine In 4ch Amp

[tboyko]

I installed a four channel amp to power my speakers and have been getting an absolutely horrible amount of engine/car noise through my speakers, even when the engine isn't running. I have already done quite a bit of research and troubleshooting, but cannot resolve my issue. Here is my setup.

-Alpine 9825 HU with 4v Pre-Outs. I'm using existing volvo power and ground wiring.

-4AWG power wire from battery to trunk. The routing of the power wire is from the battery, up and across the back of the engine compartment, through the passenger side firewall, and along the passenger side of the car to the trunk. The ground wiring is mounted to a bolt I found underneath the passenger side trunk mat. I'm using the included 60A fuse.

-Stinger hyper series twisted interconnects (FR, FL, RR, RL) are run along driver side, along with remote wire and Stinger pro series speaker wire for front two speakers.

-Speakers are infinity kappa components up front, and infinity kappa 5x7 on the rear deck.

-MTX 404 50Wx4 RMS 4 channel amp in rear

I first checked all my connections when I got noise. Nothing was wrong. The noise doesn't change volume except when I adjust the gain knobs on the amp.

I ended up taking the advice of someone on this forum and hooked up my ipod directly to my amp through the RCA connection. No noise. Connected my ipod to the end of my interconnect cables (right next to my head unit. No noise. I also made one of the test plug type things where you short the ground and the signal on an rca connection and check for noise by connecting that to your amp. still no noise. Because of this I believed that it had to do with my head unit. I rewired the ground cable, both directly to the negative terminal of my battery and then later to the mount point of my ground in my trunk, but this made no difference. So I assumed that something was up with my head unit. I returned it and got a new one...but this didn't fix anything whatsoever.

I talked to someone at a local parts shop and they suggested I try putting in a relatively small capacitor inline with my ground wire on each RCA cable...possibly eliminating a problem in DC or AC offset between the HU and the amp. I did this, but it made no difference.

It's been suggested to me that it might not be a good idea to have my power cable running across the upper edge of my engine compartment and that I should just route it along the drivers side and move my other cables to the passenger side. I might have to do this if nothing else turns up to work.

does anyone have ANY suggestions for me? I feel like I have tried just about everything. (oh, I tried different mounting points for my amp ground as well). Thanks for any help!

Taylor

[tboyko]

UPDATE

I decided I might as well switch my power to driver side and signals to passenger side, since it's the only thing I hadn't tried that people recommended. Well, two hours later, no change. I honestly can't figure out what could be wrong. Please guys, any ideas?

[Bing_0]

so wait, you are saying when you use the headunit as the signal source there is horrible noise, but when you swtich the signal source to your ipod via the same rca cables, there is no noise?

if thats the case, then it should be pretty simple: swap in a new headunit and see if you have a freind with a aftermarket head, swap it in, if not, go to circuit city, get one, swap it in, test it, and if it makes no difference, return it.

but if i am understanding you correctly, that the only time there is no noise is when you take the headunit off line and plug in isntead the ipod, then the source of the problem most likely is the headunit.

b

[The Reverend]

He said that he returned it and bought a new one though.

[tboyko]

thanks for tthe advice bing, but yeah, I already tried that unfortunately. I'm thinking that it is some sort of grounding problem between the amp and tthe headunit (since the ipod isn't grounded, there is no problem when I use it). I was also told today that some head units have compatibility issues with certain amps, and that that could be the problem. I'm going to try running new power and ground cables directly from the battery tomorrow and see if for some reason i'm picking up noise through the existing volvo power wiring for the headunit...i get noise as soon as any electrical components of the car are powered on, such as headlights etc, changing from reverse to drive, alternator noise, general buzzing. I figured it was worth a try at least. What else is there to try though?

I talked to someone from MTX today and they suggested running a ground cable from my amp to my negative terminal of my battery instead of using the car frame, sounds sort of extreme. Any other ideas? I appreciate the help guys.

[bogelo]

I was also told today that some head units have compatibility issues with certain amps, and that that could be the problem.

There is no such thing as incompatibility, IMHO. Use a good RCA cables (twisted-pair) such as: monster cable, PG, streetwires, etc. It is good, as long as they are twisted.

Don't run your power cables and ground cables along with the RCA cables. Power cables must be far away from the RCA cables. You should run your power cables on the left side (near door), all your RCA cables & speaker cables on the center side (center console all the way back).

Get a clean ground, make sure that you're not tapping from other component' ground.

Since your IPOD is not connected to the car ground (do you use battery or cigarette lighter?), it is likely not to make ground-loop noise.

Do you install your amp yourself? Trust me, usually it's the RCA cables problem interfering with power cables. Look for any intersection between your RCA cables and power cables. If you don't have twisted pair, only an intersection with the power cables can cause noise.

[Bing_0]

oh my bad...

sounds like a ground loop issue...but the you said you rewired the headunit right?

have you tried a ground loop isolator? pick one up at radioshack and plug it into the rca before the amp, i have used it before and in some occasions, made a big difference.

b

[tboyko]

Finally, the problem has been solved!

Before I said I had rewired the ground and power, but I never rewired the ignition switch. Turns out that noise was in the ground, power, and ignition switch, so if any particular one was connected, I was getting horrible sound. I rewired everything and it's great now, but I just have my ignition wire from my HU hooked up to the power that I rewired. Is there any way to rewire the ignition, but still not have to worry about noise?

[Bing_0]

this is kinda unusual, did you use a harness?

b

[tboyko]

I spoke too soon. Seems once I got everything put back together, I have horrible horrible noise once again. I'm not sure if I was failing to test for no noise properly with the new lines or if they started picking up noise as well once i got them all in place, but i'm extremely frustrated. I'm going to retry running lines outside the car like before and see if that resolves my problem.

[Bing_0]

i assume you have tried a ground loop isolator and used a harness?

b

[tboyko]

Bing,

I actually didn't use a harness because the shop I bought stuff from gave me the whole "your volvo has an amp that is going to mess everything up" story even though it doesn't. I basically spliced from the volvo cabling directly to the HU harness.

I haven't really tried an isolator because I've heard they degrade audio performace, and that is the last thing I want to do when I've already invested money in nice equipment. Someone told me to make a little device that might be similar to an isolator (it basically places a .1 mF capacitor inline with the ground on the RCAs) but it made no difference as far as I could tell.

I tried rewiring the power and ground again yesterday and I was getting noise once again. It seems that I must have not tested properly when I did this before and essentially tricked myself into thinking that I had found the problem :/ .

Something interesting though is that I tried hooking my ipod up to the end of the RCAs again last night. Though as I said before I got no noise from it, when I put the ipod down on the seat instead of holding it, there was a definite buzz, though it was much quieter then when the HU is hooked up. I guess the ipod grounds out through me when I am holding it so it doesn't buzz? I'm going to try to hook up directly to the amp today and see if i can make that buzz as well. Any ideas guys?

[Bing_0]

those people that say ground loop isolators hurt audio play back are in some snese like those people who claim they can feel a 1hp gain or loss...

i have used it in installs and so have other quality installers around hte country, and even the radio shack one works fine if you are concnerned with sound quality that much, there are audiophile quality isolators around like ones built by navone engineering...

but i would say your problem lies in the hardwiring of your headunit, causing a ground loop somehwere...

why not give an isolator a try and see for yourself? if ti doesnt work, return it

b

[tboyko]

Hmm, maybe I should try that then, just hit up a radioshack.

How do you think the hardwiring of my headunit is messed up? I can tell you what I have connected right now....

the blue power antenna line is connected to my blue HU line

the antenna is connected through the antenna connector

the red/black volvo power line is connected to my yellow HU power line

the yellow/purple? ignition wire to red HU ignition wire

black ground to black ground

RCAs to rear

cd changer to 1/8th inch adapter plugged in....

I have disconnected all but power, ignition, ground, and one rca to test for noise and i get the same problem. also, as i said before, i have run new ground and power but this made no difference.

[tboyko]

Another quick question... is a ground loop isolator going to fix my whole problem? I do have a constant hum that comes from somewhere in the engine and the headlights and other components, but i also have the alternator whine and clicking when I shift to reverse and whatnot. Will a ground loop isolator take care of all of this?

I'm basically having a hard time figuring out what is causing the noise. If it is a ground loop feedback problem, why am I getting noises other than just a consistent buzzing? My understanding is that what happens is that two audio devices have different grounding potentials (on their actual power lines) so because of this difference, a current flows down the grounding wire of my RCA cables to try to compensate. So wouldn't this just cause a consistent buzz and not pick up headlight noise and everything else?

I'm beginning to hate analog....