Amplifier buzzing

After installing an amplifier I am getting a buzzing through the speakers. It is related to engine revs, doesn't increase with volume, but thankfully it cannot only be heard when the music is not on and the car is stationary.

I have been very careful not to route the RCA cables (triple shileded) near the battery power lead and although the speaker cables are occasionally within a couple of inches of the amp power cable (unavoidable due to the power connections and the speaker connections being on the same side of the amp), moving them even closer makes no differenece at all. Any one got any ideas?

Thanks

Two forms of screening gentlemen, one is anti-static, the other is anti-magnetic.

You have screened cables, hopefully you are not using the screen as a signal cable.

You can try connecting the screen at one end, and leaving the other end disconnected, then try connecting the screen at both ends, if the first way didn't solve your problem.

As always it is much better to solve the interference at source if you can, rather than trying to exclude it from a device.

Check your normal alternator etc, and don't forget the fuel pump, as most people do !

Electrical noise in a car is an absolute pain to get rid off.

I tried all of the standard Alternator / Fuel Pump / Earthing stuff etc etc, and eventually bought one of these.

http://www.m-99.co.uk/Car_Audio/Noise_Suppressors/noise_supp ressors.html

I bought the NS21 and it got rid of all of the noise. I was a bit reluctant to put one in, as I'm a bit of an audio freak and thought it would destroy the sound quality, but all it did was remove the noise!

It's been in two cars now, and has worked in both

Two second job to install - just plugs in-line with the Line cables, and I put mine at the amplifier end.

I played around for the previous four cars before this one (a E36 328, an E30 M3, a Peugeot 406, and an Audi A4) and couldn't get rid of all of the noise whatever I did (328 had 12 seperate amplification channels!)

Best £20 i've ever spent on car audio .

I found that the proximity of the head unit to the dashboard dimmer has a bearing on induced noises.

The dimmer must produce some RFI which can affect the stereo, try altering the dimmer control to see if it alters.

I'm seriously considering a balanced pre-amp at the head unit, as I can run this down the car and pipe it directly into the balanced input on my Rockford Fosgate EPX2.

Running balanced (like microphone cables) will eliminate the bulk of induced interference, and the higher level output by the balanced pre amp will help further, as you don't need as much gain at the receiving end.

Andy

Well, I've been doing a bit of investigating and found that the buzzing increases and decreases with the gain control. Does this give any clues as to what exactly is causing it? At least this means until I sort the problem I can minimise the noise.

I tried fitting a suppresor, to the live out from the alternator, basically a capacitor (250micro farrad) wired between the live out and ground. The fitting instructions said to connect it to the wire that is only live when the engine is running. Now since there are only two wires, a thick one which is live all the time and a thin one which isn't, I connected it to the thin one. It has made no difference at all. Should I have connected it to the thick wire?  The thin one seems too thin to carry any kind of current, does anyone know what it does? Also I couldn't find an earth connection for the alternator. Oh for a wiring diagram!!

If the noise is increased with Gain, then it is being introduced before that stage in the amplification - i.e at the pre-amp stage.  This would suggest that the noise is being introduced by the line inputs.

All of the information I've read on this in the past suggests that you should never earth directly to the battery.

Well, I can't imagine how the RCA cables are picking up any interference since theyt are rounted on the opposite side of the car to the power cables, infact the are run alongside the standard speaker cables. I will check them out anyway. Oddly enough the only speaker which isn't affected as much is the front right? Can't think why this would happen, both front maybe, but only one!?

I will try playing around with the amplifier earth.

I'm not sure I want to start removing wires again. It took me ages to get them in and I have the cuts and grazes to prove it. Lifting the carpet is a pain especailly since I haven't been able to work out how to disconnect the accelerator pedal from the floor.

TBH now I have set the gain to 'Nom' the interference is a lot better so I'm in no rush. It have spent enough time messing around with the car for the time being and I could do with a break.