Just finished building a new sub enclosure, and got my system back up and running, with a new amp. Only to find I am now suffering interference, which I think is coming from the alternator, its certainly related to engine speed. Any quick fix solutions? Anyone else experienced this ?

Check all your grounds! Make sure they are clean.. you may have to fit a supressor to stop it, if it is alternator whine... sorry too early for me to think about all the things to do, try doing a search for alternator whine..

David

Who's the amp manufacturer? Some have slight peculiarities to ways of getting rid of whine.

Its an Infinity 6 channel amp, driving fronts, rears and subs.

have you run the power and signal cables down the same side of the car? If so at least separate the rca and power cables. If amping the front speakers, these ahould ideally be run down the middle, but if not they should be run with the rca cables and not the power.

Also make sure the power runs down the same side of the car as the battery is located on and does not cross the engine bay past teh alternator.

Infinities normally have very good internal noise supression from the power, so I think Adam's suggestion's probably right.
The thing to do is disconnect all signal inputs and then try again (with the engine). If there's still a noise, it's coming from the power. If there's no noise, it's coming from the input signals. Probably. The cables should then be routed as Adam suggested - away from power!
If there's rev-related noise with no signal connected, check the earth. You've probably already done this, but it seems to me it's always where I go wrong! Earth cable should be at least the same size as the power cable, as short as possible but less than 1m is probably OK especially if there's a good earth point directly to the chassis.
Isn't there a guide somewhere on this? I'm sure I've seen one before - can't remember where though :D

http://www.mobileaudio.com/rac-faq/

David

Thanks for the help guys, all useful suggestions. I have run the RCA cables down the middle, with the power down the same side as battery (nearside). The speaker cables run up there respective sides, so one does run near the power cable. I guess pull apart and more carefully fit back together, and test as I go. Its definitely engine speed related. When I did the first tests I didn't notice, because its only audible between songs ;)

As far as I remember it's actually possible to pick up noise from the transmission with the cables running next to it. Seemed pretty remote chance to me at the time! I have power down the left, RCA up & downs on the right (a bit squished - 4 pairs!) and the speakers on their respecive sides. I get no interference at all from it - well, I can hear the hard-drive spinning if it's up very loud with nothing playing, but that shouldn't be a problem...

I was reading on here about adding extra earthing straps due to the factory ones being a bit on the sh1te side.
As I had a bunch of cable left over I tried it. The result has been a smoother running car, better engine sound and an annoying buzz on the left channel of the ICE disappeared.

Basic description ... found fuller one on i-club, but cant remember where.
Run from the battery a series of extra earth cables (75amp +), and go to the following points. Each earth point on the front struts, a selection of fuel rail retaining bots on the inlet manifold ( i used 3) and to the bolt that holds the alternator and air con together (not an adjusting one).
On top of this you could also take a point into the car and earth all of you ICE to that common point.

This may have only produced good results because I had a badly earthed car ... who knows, cable is cheap though.

[Edited by Nigel Bowles - 11/25/2001 9:22:16 AM]