Yet another stereo grounding issue

I have read the threads on ww.com about grounding your stereo equipment to the battery, but my situation seems a little different:
I have two batteries (one deep cycle for the stereo when i'm beached, and one cranking battery for starting) hooked up to a perko switch for the starter/alternator. The accessories/stereo/etc power and ground wires are all hooked up directly to the deep cycle battery. The problem is, when the engine is running and the perko is set to battery 1 (the cranking battery) I get little to no hum in the speakers. However, when I switch to bank 2 or "all" to charge my deep cycle, I get a loud hum which I presume is a grounding issue.

Why would this happen? I have the deep cycle ground wire running to the cranking battery which is what perko recommends, I just don't understand how the humming is only isolated to one battery...

Please help, I'm getting so frustrated!

Refer to the pics below and use them as a guide to rewire your head unit to the amp power lugs. These are a few examples of common stereo installs, and there are a couple of iterations of stereo power switching.

Wiring the head unit to the amp as shown has proved to be the best way to prevent noise in an audio system.









What is your charge voltage when the motor is running? If you have ever switched your Perko switch to OFF or past OFF with the motor running, you could have blown a voltage regulator diode. That can make nasty noise, and will cause other problems as well.
Phil
Kicker

Phil, thanks for the diagrams.... What is the issue with grounding to the batts? I have three amps and three capacitors that are all grounded to the batts and don't seem to have any issues. The only odd thing I see is when we plug in the on-board charger all the capacitors stay lit....

I've run the switch past off a while ago.... what noise would it make and are you talking about the charge diod in the alternator?

(Message edited by aaudii5150 on July 15, 2009)

Brett-

Amps should be grounded to the batteries. We advocate moving the radio / headunit power...

Moving the head unit power from the batteries to the biggest amp puts its power and ground at exactly the same voltage potential as the amps, eliminating ground plane voltage differences that allows hum.

Phil
Kicker

Phil thanks again.... I did edit my post and added one more question..... When you get time....

Thanks Phil, that first diagram looks like it fits the bill. Will make the change next time I'm up!

Brett-

As I understand it, a couple of things can go bad in a charging system. You can end up with way too high a charging voltage for one; that happened to me in an automobile several years ago... Talk about bright headlamps!!! Until they burned out one night... voltage was pushing 20.

If you blow a rectifier diode, you introduce AC into your electrical system. This will be a while or buzz that goes up and down with engine RPM.

Take that with a slight grain of salt. Someone else may very well be able to better and more fully explain the exact how's and why's on the voltage regulator failure. I may have not explained something above with regards to the details of the regulator totally correct. The basic cause thought is the same; if things weird start happening after accidentally switching past OFF with your battery switch, go to the voltage regulator as your probable source of problems.

Phil
Kicker.

Phil, I think we're in the clear.... I was having major voltage issues, pulled the alternator and had it bench tested, passed. Ended up replacing 4 out of 5 batt, new on-board charger and everything has been OK.

While I was working through this issue I was told all kinds of stuff(main reason I pulled the alternator and had it tested). Just trying to get the straight scoop from someone who might know what they're talking about.

Thanks again