Electrical interference on Audio install
 

To set the scene:
Alpine HU, 4 channel amp in boot.
Amp powers door speakers and 2 newly installed roll bar speakers.
RCA connections from HU to Amp.

Problem:
When running just the door speakers from the Amp, everything is fine. When I plug in the rear RCA's to the amp and power the rear speakers I get the "alternator" noise but from all 4 speakers.

What I've found so far;
The problem is not the speaker wires. I've had just the fronts connected and then tried moving the RCA over to the rear socket on the Amp and just powering the rear speakers and they're fine. That rules out the front RCA lead, the speaker wires, the front output of the HU and both inputs on the amp.

What I'm going to try next;
1: If I use the known working RCA lead and take the output from the rear output on the HU, that will rule out the HU as a cause.
2: If I disconnect the front RCA and just use the rear RCA (Trying it in both outputs from the HU) that will tell me if it's that RCA that needs relocating.
3: If that doesn't reproduce the problem then I investgate the possibility of an earth loop so I will run an earth from the HU to the same earthing point as the amp uses.

Is there anything I'm missing? Aside from the rear RCA picking up noise or earth problems, what else could it be?

Ta

i have same issue on mine.
i've come to the conclusion it's going to cost me an alternator.

i tried alot of things to get rid of the whine on my install; even a supressor which did naff all (£15 well spent:().


alot =
bypass my installed RCA cable
bypass installed amp wiring kit (cables over roof direct from battery to amp)
lots of work to chassis grounding
extra alternator grounding cables
extra battery grounding cables
soldered RCA ground to each other & then onto HU ground (i heard rumours of Pioneer units and a blow ground RCA trace causing alt. whine)


my RCA cables run down center tunnel, 12v power for amp down right side of car, amp ground to the rear brace bar bolt (or a shock bolt; i cant remember).

i gave up in the end. never did solve the issue. luckily the whine isnt that bad for me; it only noticeable on quiet parts of tracks.

Well, I spent the day chasing my tail and coming up with nothing.

Then some evening searching threw up this...
http://www.audiogroupforum.com/csfor...ead.php?t=9157

Ordered a set of these, fingers crossed.
http://www.google.co.uk/search?sourc...0be71e987e5a8d

Hope that sorts it .... electrical interference is the work of the devil. I did reply on the other DIY thread - but have always run seperate amps for front and rear speakers / sub ..... if the problem is something RF designed in, that sucks!

I've tried everything. It's when that 2nd set of RCA's get connected that the problem appears which is why that thread seems to stack up.

If the leads don't work then I'll eBay my 4 channel amp and get 2 x 2 channels instead.

Although to be honest, the noise is only noticeable between tracks. It's just the fact that it's there at all that's driving me mad.

However on the plus side, I've re-routed the RCA's, tidied up all the HU wiring, learned loads from the wiring diagrams in the service manual (and think I know where to look to fix my qube dash not dimming with the controls). I've also tidied up the install of my modfry dash mount/iPhone holder and leads while everything was apart.

Tomorrow it's the brakes and a good clean.

Just a thought - do you definitely need to use the F/R fade?

If you use one set of RCAs and a splitter (or set the amp to the appropriate settings) you can run all 4 speakers from just 2 RCAs. Worst case you can "set and forget" the Front and rear gains on the amp.

Which model amp is it?

Yes because unless you run RTA or something ... how often does anyone really fiddle with balance / fader settings?

Good call Simon!

Try two of these or similar

http://www.maplin.co.uk/phono-2-plug...et-cable-29191

It's a fair point but given how far I've gone now, I want to know the cause and fix it.

I know I'll probably never mess with it once it's in and set but it'll always play on my mind and drive me bonkers if I don't do it right.

Thanks for the suggestion though.

Interesting...Twisting the 2 sets of existing RCA's together along their length certainly seems to reduce the noise. Unfortunately I can only do it in areas I can access so I have high hopes for this new cable.