Low level hum?

I think I should add something to stevdarts post just to make sure there is no confusion.  When he says to twist + and - around each other, he does not mean to strip the shielding off the wires and twist them together, leave the shielding on and kind of braid the wires.

Now, a question for stevdart.  I emailed Perry Babin, the guy that runs bcae1.com about this and he said that when the deck turns off, the speaker outputs from the onboard amp are left floating, meaning not electrically connected to anything which can allow the transformer in LOC to pick up noise.  How does that sound to you?

I would say that Perry Babin tops the list of people I enjoy learning from.  I'll remember that.

My experience with LOCs is limited, but I haven't heard any noise problems as you described.  I will use long lengths of twisted speaker wire to connect the LOC, and place it close to the amplifier.  The connecting RCAs are one foot or less in length.

You say that just turning the deck on, with no volume at all to mask the noise, stops the hum?

Hummmm.......

The LOC in question is not grounded to chassis, is it?  And is it one that is of high quality and has isolated circuity to prevent ground loop?  Whether it is capable of picking up noise when the connected deck is off or not, it is still connected to the amp via RCA cables and has to remain a suspect...as well as all grounding involved in the install.

yes, simply turning the deck on will stop the noise.  I'm starting to think I'm crazy cuz nobody else knows what I'm talking about.  The noise isn't alternator whine or any other kind of inducted noise it is as though a test tone cd was playing a low frequency track on repeat but it is very loud.  As soon as you turn on the deck it goes away.

The LOC I used when this happened last was a peripheral, before that I believe it was install edge. 

Perry's explanation is really making sense to me because it is the only possible cause I have heard yet that has to do with the radio turning on and off any other noise I would be able to hear under other conditions but with the deck on (revving engine with volume down to here alternator whine for example).

Oh, then I misunderstood what he said.  I read that to mean that the LOC could not pick up noise when the deck is off.  But now, by what you just said, I realize it is entirely the opposite, that it can pick up noise because the deck is off.

I had thought that the LOC could pick up noise either way...deck on or deck off...if something was not up to par with the setup.  But this sounds like a voltage mismatch hum, this sub frequency tone.  Such as when the amplifier gain is set too high for the deck's output signal.  First, test to see if the LOC is the culprit (or anything upstream) by removing the RCA inputs at the amp.  Some good troubleshooting has been given in this thread, and you should now work through a troubleshooting procedure to isolate the cause.

Yeah i dont really know how a transformer works or anything so I can't say why this is true but the next time I have a customer who wants to do this typ eof setup I will definitely put on my investigators hat and do some pokin around..  Thanks everybody for all your thoughts and ideas.

One last thought.  People ask me alot why I chose the career I have instead of doing something else that I guess is more meaningful.  This type of thing is why.  There are so many other things you can study and fields you can work in that have solid concrete answers to your questions that you can look up in a book very easily.  But it seems like so much of this industry is kind of up in the air and you really have to put in some time to really understand it instead of just sayin "hey there it is, it works, forget it".  Thats exciting.  Maybe im just a rambling idiot who puts too much thought into things, yeah im gonna go with that.