adturb

Hello,

I'm having a bit of a problem with my 51 WRX's standard head unit (no pre-outs!!!). I have taken the front speaker outputs to the high input of a 4 channel amp. The amp then feeds the front speakers and a 10" sub.

When the engine is running, as the revs increase, so does the pitch of the whine. So far i have tried to re-run the power cable, re-run the remote wire and head unit ground as a twisted pair (suggested by a mate that i cut the normal earth on the headunit and earth it at the amp instead- did help a bit), but it's still there.
If i use the RCA inputs on the amp (from an ipod) there isn't a problem.
Any suggestions on how to remove this interferance without replacing the headunit?! I'm starting to seriously consider fitting a forester adaptor plate and my old headunit, or buying a £200 Hong Kong DVD special to fit.

Cheers

chiark

Sounds like a ground loop...

Four thoughts (in a semblance of order):
- ground the amp better to a better point on the chassis (scoobs have some points on the chassis which aren't terribly well connected electrically)
- Uprate your engine ground cable, and battery ground cable.
- see if you can find a ground loop isolator for high level inputs - not sure if such a thing exists.
- use a speaker to RCA level converter (this might not help! - depends on what is causing the noise)

scoobyman95

put the shorest posable ground on the amp if that don't work put filters on the rca cables

scoobyman95

also you have to make sure the power cables are not ran near the rca cables if so that is your problem