Installed amp, but getting engine noise...

[Six6siX]

I fitted a 4 channel amp in the boot the other day, powering front components and just some rear coaxials at the moment.

I've run the power cable and remote lead down one side of the car and RCA leads down the other side and used a ground point in the boot on the chassis, but for some reason I'm getting engine noise (ie increases and decreases with revs) - inteference like - when the amp is on. Its only audible at lowish volumes, and can't really be heard when driving normally, but is still annoying.

The sound comes from both front and rear speakers.

Any ideas what it could be / what can I do to troubleshoot?

Ta

 

[Six6siX]

is it decent cable?

The power and ground cable are both 8 AWG and the ground from the amp is less than 0.5m away. RCA cables are shielded as far as I know and the speaker cables are decent.

Were there any other cables on the side that you ran the RCA cables down? Might be picking up interference from another power cable of some sort.

Thats a good point, never thought of that - I'll have a look.

If it's a whining noise, it's alternator whine/ground loop.

Usually caused by audio components being grounded in multiple places - ie head unit up front of car, then the RCA leads go to the amp which is grounded at the rear - causing two ground points and voltage differential between them.

Check your grounds are all OK and as short as possible. Try adding an extra ground wire from the head unit casing to the chassis. If not, try a wire between head unit case and case of amp.

It is a sorta whining noise that increases and decreases with revs, yeah. I'll check all grounds and try different points, thanks.

 

[Six6siX]

Update on the situation, finally had the time to do something!

I got hold of a new headunit - impulse buy (w00t) (only has 1 pair of pre-outs tho - old head unit had 2 pairs) and connected the new one up using the existing wiring and amp to power just the front components. Guess what - no whine!

Waiting on a set of Y-splitters to feed the rear channel of the amp and I can see for sure if its cured. At this moment its looking like the headunit pre-outs were damaged.

When installing, I connected the RCA's last, but it was a 2nd hand unit in the first place so may have been inherited damage that never surfaced till now...

Will update again when fully connected, cheers for the help people

 

[Six6siX]

Well, I connected up the rear speakers and there is no humming at all. Problem solved. Must have been the headunit