Whistle and rattle = unhappy Captain

[legoless]

The best earth point for the amp (if it under the rear seat is one of the rear seat belt anchors. You still have to clean the paint away though. I had same issues with mine and this cured it along with seting the correct gain setting on the amp I have a pioneer head unit with 5V pre outs. the namp was set to about 8V so I backed it off to 5 and all is now fine.
I also lurk on thetalk audio forums and here are a couple of useful pages ....

http://www.termpro.com/articles/noise.html

http://www.talkaudio.co.uk/vbb/showthread.php?p=1949352

[Captain Jack]

What a pain in the butt! I started off with running an earth wire (8 awg) from under the rear seat (ground point for the amp - also 8 awg) and tried connecting it to the alternator - no improvement. So, I connected it to the head unit chassis - some improvement. I thought, I'll cut the original ground wire from the head unit's harness and use the amp's one - this showed the best improvement but still buzzing a bit. By accident, the aerial connector disconnected itself from the HU - this halved the buzzing noise but could still be heard. I guess, I'll need to earth the aerial properly somehow. Any ideas?

I went to Halfords and bought this noise suppressor thingy, which was basically a 3 uF capacitor. The instructions on the back weren't especially clear, but suggested that I bolt the capacitor to a ground point and connect the brown wire to the alternator's +12v output - is that correct?? I don't want to blow anything up, so I didn't do it tonight (driving to Newquay tomorrow!)

Currently, I still have the ground loop isolator in place as there's still too much buzzing for my liking without it. Next is to fit the suppressor. If that doesn't work, I don't really know what else to try.

Funnily enough, the 2nd Kenwood subwoofer amp doesn't suffer from this buzzing noise (rear speakers), but I connected this to the power point of the original JBL amp. I can't connect the main one to it as the wiring is nowhere near big enough to handle the current - they'll melt!

I bet I'll end up ripping the HU out and putting a proper one in - but that's the last thing I want to do as they are fairly pricey for a decent Alpine (like the one I had in my first Pug).

Aaaaahhhhhhhh!!!!!

[legoless]

Any luck Capn?
I`m not clued up on capacitors :/
All you can do it check the earths as it seems to be the prime cause of radio noise esp as the amp connected to the original earth doesnt suffer

[Captain Jack]

No, I haven't had a chance to work on it since my last post. Will try connecting the main amp to original wiring temporarily and see if the problem is still there.

Got a few other suggestions to try from this thread and will come back to you then.

[Captain Jack]

OK, fitted a 3uF capacitor to the alternator yesterday and the whine has gotten much better once again, but still present without the ground loop isolators attached to the amps. Only happening now when sesitivity is turned all the way to the max though (0.2dB), so with every thing I do is improving matters!

I need to properly ground the aerial as well, as I know that it introduces more noise if it's attached - any idea how?

[mjb]

I need to properly ground the aerial as well, as I know that it introduces more noise if it's attached - any idea how?

I'd suggest stripping the plastic outer insulation from the coax, solder a wire to the coax shielding, then attach that to the body somewhere/somehow

[Captain Jack]

Strangely enough, there's already a tear in the outer sheath so I can see the shielding. Can I connect this to the same earth point as the amp and the HU?

[mjb]

I should imagine so