Aftermarket stereo: wiring/grounding/noise

[drkblubeast]

Hey guys,
After installing my aftermarket stereo and wiring everything up, I get huge amounts of noise/alternator whine/etc. What I had questions about is my grounding... I bought a Metra wiring harness for factory amp integration (http://www.amazon.com/Metra-70-8113-Wiring-Harness-Integration/dp/B0007WRQQ2) to connect to my new HU.

However, the HU has two ground outputs - one is a black wire that goes to the battery (hooked this up to the black "ground" wire of the harness), and another one labeled "ground" with a metal ring terminal. I connected that second one to the "amplifier shield ground" of the harness (I believe it corresponds to pin 10 of the stock radio connector (http://crutchfield.custhelp.com/app/answers/detail/a_id/7456/kw/2002%20toyota%20celica)). After making this connection, I heard some noise when testing the radio (with key in the ACC position), and hooking up the same wire to a metal screw on the chassis seemed to make this noise go away. But now when I start the car I get awful alternator whine.

What did I do wrong? Would doing the wiring kit noise mod help?
Thanks for any help, and happy Sunday.

[chillan420]

are you using the radio to power the speakers? the factory amp? or aftermarket amp? do you have a pioneer headunit?

unless you have a premium stereo with factory amp. you have a ground loop issue. here is some noob info for the 50hz wine your hearing.

http://www.termpro.com/articles/noise.html

[drkblubeast]

No, it's not a Pioneer HU. It's from a company called Sumas. I'm not using this HU to power the speakers - it's the factory amp. The HU itself has two pre-amp outputs (L&R), so I used two RCA Y splitters to connect these outputs to the factory amp inputs.

I'll read that article to see if it helps, thanks.

I guess what I'm mostly unclear about is why my HU has two wires for ground... One of those I can tell goes to the black battery ground wire, but there's another one with a metal ring on it. Again, I connected that one to the "amplifier shield ground" of the harness and to a metal screw on the car...

[drkblubeast]

Some additional information: it seems that the wiring harness itself is introducing some noise. When I unplug the harness and start the car, there's no noise. If I plug in the wiring harness with RCA amp inputs disconnected (everything else like +12V, ACC, ground, etc is connected), there is some static, but it is not alternator whine. The noise does not change when I throttle the car. When I connect the harness amp inputs to my HU pre-amp outputs, the noise gets worse and the pitch gets higher as I throttle (alternator whine).

Any suggestions?

[chillan420]

one is signal ground, and other is chassis ground. the signal ground will be the noise one.

[drkblubeast]

Thanks. I also just found a post (http://www.newcelica.org/forums/showpost.php?p=2934194&postcount=63)that answers pretty much of my ground questions and the difference between the 3 different ground on the R4 connector.

From what I've been reading, the Schoche TA 03 wiring kit noise mod worked for someone who had a Metra harness, so I guess I'll give it a shot this week and see how it goes. Fingers crossed...

[drkblubeast]

Did the mod with 500 ohm resistors, got rid of 99% of the noise. Thanks for the help!