....so in the last month I had mounted an aftermarket amp in the trunk and a new head unit in the dash.
I had some engine noise that was noticeable only when the source was off and the fan setting was low and with the windows closed. To someone other than a p-car owner, this may sound like a turbo whiz but it irritated me to no end.
I then bought new power cable for the amp and routed the power cord all the way around the trunk to take the longest path away from the RCAs and yet get to the battery. I still have engine noise.
The only thing that I can think of but have a hard time believing to be true is the remote power lead to turn on the amp. This is a tiny gauge wire that passes from the head unit to the trunk along the same path as the RCAs. Could this tiny gauge wire still carry enough oomph to make engine noise?
The next thing that I think that it is but haven't worked on yet is the ground for the amp. Currently the amp is sharing the same post as the ground being used for one of the headlamps. I pulled back the carpet and there is was in front of me so I didn't bother tapping a new ground. It is very tightly pinned down but I didn't know if the amp needed its own independent ground or not.
The RCAs weren't cheap and are shielded. What else am I missing?
Anyone that knows our trunks will know that the location of the positive battery cable and the distance for passing RCAs into the cab of the car is at best, 3 feet apart. Am I still too close to the main power cable?

 

It has nothing to do with the remote cable. Try a different ground. Also, check your battery voltage, if the voltage is low it can cause a whine as well. Probably a gound issue though

Have you tried a gound loop block?

Christian

 

Um....what?
Since I don't know what a ground loop block is, I would venture a guess that the answer would be 'no'.
It sounds simple in its description but I have never heard the term before. please teach me something new.

 

from what i have been told ground loop is cause by different voltages at the grounding point. usually the groud at the amp is not as good as the ground at the source. you can check this by using a volt meter. easy fix is run the source ground to where the amp is ground or try a jumper lead from amp ground to source ground. oh the source = radio or head unit.

 

yeah, this is where aftermarket stereo installs get fun.. heh.
you first have to isolate where the whine is being introduced - head unit or amp.

Turn your car stereo on w/ engine running, listen for whine. unplug the RCA leads from the amp. Does the whine go away or stay? If it goes away, it is coming from the head unit. If it stays, it is coming from the amp.

If it is coming from the amp, try installing a large stiffening capacitor on the battery+ lead to the amp. also try changing your amp ground point. also try isolating the amp chassis from touching car metal.

If it is coming from the head unit, try these:
-unplug the antenna lead and see if the noise stops.
-try a different ground point for the head unit
-try installing noise filters on the power leads to the head unit
-try installing a ground-loop isolator on the RCA leads (get one at a car stereo shop)

let me know what you find.

 

I think that I have more to look at than I thought.
I have the amp mounted to the floor of the trunk by way of brackets that I made. I cut and folded aluminum into brackets and passed them through the carpet and mounted the amp to them. I may need to put isolators in there.
Checking the ground points seems easy enough to do and is quite a good tip for those doing their installs themselves.

 

It is all about the ground. As Porsch3 said, you gotta figure out where the whine is coming from. First, make sure your amp ground is solid, to the point of sanding the paint off and *securely* bolting it down. If that doesn't fix it, start looking at the RCA's. From what I've read, the cheap RCA's are actually better as there is less distance btwn the wires, resulting in less potential for interference. I agree it is somewhat anti-intuitive but that is what they say. Do a google on ground loop noise and see how to isolate the source.

I would avoid filters because all they are doing is masking the underlying problem.

 

I put an JL Audio amp in my cab a few months ago, and had a bad whine. I assumed it was either interference on the RCA cables, which were much longer than they needed to be and could act like an antenae, or a ground loop. I tried isolating the cables, and redid all the ground to a common ground where the battery was grounded. Still had a bad whine. Then I tried to adjust the input sensitivity of the amp ( I had bought it used on Ebay). It utnred out the previous owner of the amp had the input sensitivity turned almost all the way up. I readjusted the sensitivity per the JL instructions (lowerd the sensitivity all the way, then turned the head unit to 3/4 volume, then raised the sensitivity such that the volume was about as loud as I would ever listen to it, some waht a crude method but it worked), now no audible whine at all. You may want to try this, it worked great for me. If the sensitivity is too high it picks up even the slightest noise.

 

I had the whine really bad when I had the gain turned up high like you mention here. It's turned down to about half way but the whine is there.
I haven't been able to do anything per all the suggestions and probably won't until Saturday. Again, the whine is only heard when all the toys are off and the roof and windows are closed. I just shooting for perfection here. Some of you may not even hear the noise.

 

I don't allow any whining in my pcar... stereo, female, or otherwise

 

I'd like to jump in here if I could. I am getting a whine from the climate control blower. Could this be caused by my aftermarket amp/head unit and possibly solved the same way?

 

do yourself a favor and go to radio shack, walmart, or a best buy and buy yourself a ground loop isolator for about $15-20... plug it in to the rca that goes into your amp and the whine should disappear.. don't worry or frustrate yourself by trying to isolate the wiring this should do the trick. if you have a 4 channel amp you'll only need to buy 1.. plug it in and start the car, the whine should be gone. if it doesn't work return the product and then try to track down the wire. i've done three aftermarket radios in three different porsches and always got the whine, all solved with buying a ground loop isolator. let us know if that works...

 

opps forget it... looks like this was an OLD post...