Surpression nightmare.

[andy 0]

Having problems with my stereo, it worked fine before but now I've installed components and an amp I'm getting horrendous electrical noise breaking through. When I disconnect the RCAs from the head unit the noise disappears, so I thought the head unit was to blame, swapped that....same thing happens. Put a surpressor in the power feeds to the head unit and it's still there, disconnected the alternator today, still there. Looking at ht leads now I suppose, is this really likely to be the cause?

[coolrado 0]

try running new grounds to the head unit and amp and make sure they are connected to very clean paint free metal

[NG 0]

U need a better ground !!

[smarkham 0]

Could also be down to the alternator needing a re build

[andy 0]

Could also be down to the alternator needing a re build

 

Ran the engine without the alternator connected mate, noise the same, so alternator eliminated for now.

[smarkham 0]

Yeah its always worth checking. It could be a bad earth on something else though its not always down to the amp or stereo earth. Maay be worth checking the plug leads

[andy 0]

Right, a happy man now! Just put a heavy guage cable earth cable from the head unit cage down to the earth stud in the passenger footwell, 95% of the noise has gone. Will wire it all in properly tomorrow. Can anyone tell me why (technically) a bad earth should cause noise pickup?

[Supercharged 2]

Have you also run the RCA's well away from the power going to the amps..?

[andy 0]

Yes, RCAs are well away. Trying to tidy all the wiring up today but having problems again. When I touch a known good earth to the outside cage of the headunit the noise mostly disappears. However when I connect the good earth to the actual multiway plug earth, the noise is just as bad as ever. Its not normal to earth the case of the stereo is it, surely that's done internally? Could dodgy HT leads still be the problem? Maybe I'm just shielding the headunit when I ground the case. aaaaagh!

[andy 0]

Help please chaps, could HT leads cause interference on my stereo...?

[Supercharged 2]

I think the leads have 5K Ohm resistors built into them? - maybe worth testing...

[andy 0]

Will try that, are the resistors there to provide supression or is the resistance a necessary characteristic of an HT lead? I'm, thinking the only thing that can possibly be causing interference with the alternator disconnected must be the HT. Thing is the car runs absolutely perfectly and I'm therefore reluctant to replace the leads (at great cost!) if they are not providing the interference!

[andy 0]

Replaced the ht leads, problem still there, what else could cause this intereference. I've tried two different amps, two different head units, two sets of phono leads, new set of ht leads, alternator disconnected and its still buzzing away. I have only connected the amp in the front passenger footwell, not in its final position as yet. Need to get it working properly there before I start adding several metres of cable into the equation. This really is getting ridiculous!

[andycowuk 0]

are you able to check the potential difference between your head unit ground and your stereo ground? See if you have a groud loop. This can cause a hum as you r audio equipment have two different reference points.

[andy 0]

I can check that tomorrow, but I'd be surprised if there's any PD now as I've earthed the HU to the same earth point as the amp, a big stud in the passenger footwell.

[andycowuk 0]

i didnt realise they had a common earth, so thats probably not gonna reveal much.

[andycowuk 0]

I have been playing with my car over the weekend, I noticed that on the live feed to the ignition coil there is a decoupling capacitor. The connections were really bad, so I sorted it..... i never had any trouble with noise suppression, and I dont know if the vr6 has this part, but its worth a look.

[andy 0]

Cheers for all your help everyone. I have finally sorted it... :-) I substituted a mates amp and all was well, not a squeak of noise. Have bought a two channel Alpine amp today and have just wired it up now to test it and it sounds great. To be honest the amp I was using was of the distinctly cheap variety, I was never going to use it long term, just thought it would do to get things rolling! Learnt a lesson there...buy cheap...buy twice :-)