alternater noise

bballa · February 8, 2005

After installing new front and rear speakers and a four channel amp in my 2001 silverado 1500 ex cab I am getting some alternater noise (whine). Not to bad but noticeable during quiet passages. Anyone else experience this. Anyone have a fix for this. Thanks, Rich

mburnam · February 9, 2005

Lots of things can cause alternator whine. Make certain to ground the head unit well; do not rely on the ground wire in the factory harness. Puting ground-loop isolators between the head and the amp may help too. If using RCA cables, buy high quality, and make sure to run them seperate from any power wires.

One quick test...unplug the input to the amp. Does the whine go away? If so, problem must be input side (from head unit to amp). If whine still there, problem could be in amp or in output. Very often, passive crossovers (like the kind used in component speaker sets) can cause whine, depending upon where there are mounted in the vehicle.

bballa · February 9, 2005

Thanks for the great info! My system before this latest " upgrade" had zero alternater whine. It consisted of a pioneer in dash unit(DEH-P77DH) a MTX mono sub amp, 2 10" cdt subs, infinity 2 way plate speakers in the rear, factory in the front. No noise, pretty good sound. Replaced the fronts with Crystal audio components and wired in a 4 ch MTX amp to power the front and rear speakers. I wired the 4 guage power wire to the red battery accessory box, not directly to the battery terminal. Could this be the cause? I need to buy one of those posts that allow for a wire to be attatched. Both amps run off the same 4 guage,I have them split at a power distribution box, same with the ground. The deck is grounded by using the factory plug, not its own separate ground. No whine before when using the decks internal amp, just now

Halen5150 · February 10, 2005

Wait, are you saying that you wired your amp's power through the fuse box? You really need a direct cable to your battery with a fused connection no more than 18" from the battery itself. Hope this helps.

mburnam · February 10, 2005

Alternator whine can be a bear to track down. I'm assuming you are using all 3 sets of preamp outputs on your head unit? So many articles that you read about eliminating alternator noise really insist upon high-quality RCA cables. And it couldn't hurt to run a dedicated ground wire to your head unit. Any difference in potential between the amps and the HU can cause whine.

You said that you didn't have any whine before the 4-ch amp install. But even if the sub-woofer amp install did induce whine in your system, you wouldn't be able to hear it because the woofer can't produce sounds at that high of frequency.

I can't see how wiring your 4 awg power wire to the accessory terminal could hurt anything. We are talking about the red accessory access terminal under the hood where the alternator wire is attached to the main battery cable, right? That's where my amp wire is hooked up. It sound to me like your power distribution to your amps (distribution block with seperate wires running to each amp) is sound.

A search for "car audio alternator whine" on google turned up several articles on this topic. Maybe that would help. Best of luck.

bballa · February 10, 2005

Mburnam, thanks for your replies! My power cable is connected as you described and I dont think it is the problem. My interconnects are top quality MTX with "twisted pair technology" and shielding so I don't think they are at fault. All three pairs are run on the right side of the truck. The power cable is run on the left side(drivers side). I am going to drill a hole in the back for a new ground bolt and ground the amps and deck there and hope that takes care of the problem. Thanks again, Rich

bballa · February 10, 2005

It worked! : The new ground for both amps and the deck did the trick. I had first used an existing bolt from the jack mount. Sanded down to bare metal and used a washer and nut (not the one that holds down the jack bracket). The ground was tight and seemed to work fine with the one sub amp, but not when I added the 4 ch amp. I was just reluctant to drill any holes in my truck. I found out that it is necessary if you want a good ground. Thanks again, Rich