cy7878

I installed an Alpine PDX amp to the stock CR210 radio. Periodically I get a whine that was unbearable. It doesn't change pitch with the engine RPM, but does change pitch if I moved the radio around its cage. At the advice of Crutchfield prep (who thought I was installing a Blaupunkt unit that I bought from them which did the same whining thing but only louder), I cut the negative wire off the factory hardness. I was going to route the wire to the trunk ground point where my amp is grounded. But also at his advice, I tried to see if the radio would power on even without the neg wire and it actually did! The prep told me there was a chance that the radio will get enough power off the antenna to turn on. If not, I can always run the negative all the way back to the trunk.

Since I'm powering the speakers off the amp, not having its own negative power feed actually wasn't a problem. And now my electrical whine is gone.

Has anyone else done this? I'm curious.

black ice

Wierd. Never done that myself.

dave

civerson4

You should be fine. The radio is stilled "grounded" through the antenna rand/or radio cage.

J.B.H.

Couple things that should solve the problem.
1) Run the ground from the radio to the amplifier grounding point. (Looks like you have the covered)
2) Use UNSHIELDED RCA Cable from the radio to the amp...NOT SHEILDED Cables....they make high quality UNSHIELDED Cables...(I know, I know...ancient chinese secret)

travanx

why unshielded?

cy7878

What I didn't realize before about running the ground point to the amp was that still entails cutting the hardness wire inorder to rid the first ground loop. As I tried with clips using another wire I still got the whine, but what I was doing was just creating another loop.

Had I known this problem can be solved, I would not have cut the wire. Instead just pop the pin out of the hardness, which will aloow me to reinstall the pin. Now, if I have to take the amp out, I would have to connect another wire to patch the one I cut.

J.B.H.

I don't remember...but it works... (wow, if that isnt a technical answer, I dont know what is..hahah)

IamSMC

Does this sound like the reason?
http://www.mediacollege.com/forum/showthread.php?t=1388

J.B.H.

Sounds about right...I would actually use Audison or other high quality unsheilded cables...and...running a wire from the ground on the radio to the ground on the amp...should take care of the probem...
Basically run the ground the way you run the amp control wire...

J.B.H.

I will actually be hooking up my new stereo setup this weekend
Kenwood Excelon KDC x-993
Audison Srx4
Hertz HSK 125's

kjr914

Sounds like you have a ground loop...
http://en.wikipedia.org/wiki/Ground_loop_(electricity)
Grounding the radio back to the battery (or solid ground at the amp) removes the common ground wire between the noise generator and the noise receiver (in this case, your stereo receiver).

cy7878

You are right. I had a ground loop. Just cutting the neg wire off the hardness without doing anything else rid the noise. Now I think now my radio is getting a negative ground from the antenna because I have not connected anything in place of the wire that I cut.

That's the funny thing. I didn't think this can work when I heard it. But I figure I had nothing to lose by trying. The worse that can happen is the radio won't turn on because there is no negative going to the radio. In which case I can just proceed with plan to run the ground wire back to the trunk.

JBrown

This is an old ground loop trick I have been using for years. Put a small piece of wire on the outer terminal of the rca. Tape it in place . Then put the rca back in the radio. I used a barrel conector just to show you how to do it. Then ground the other side of the wire to the chasis of the radio. That will get rid of 99% of any noise.

travanx

So the idea is to ground the radio only to the amp? I have my radio grounded to the stock wire and also to the amp and get some whine sometime.

J.B.H.

Using unshielded cables accomplishes the same effect.