I have a c5 with a few upgrades. My hu is a Pioneer DEH-P4800MP. I have a PAC so I could add an amp/sub while retaining the front Bose speakers(tight budget). My amp is an old school Fosgate Punch 4040DSM. I have a 12" P2 in a subthump box. I had this all installed at a shop that is not convienent for me to return to, so I'm trying to troubleshoot and fix this problem myself.

The amp is sending a constant signal to the sub causing it to produce a low humming. This occurs along with the music being played and also occurs without any other input such as on the aux input setting w/o any aux equipment hooked up. Most of you probably know this is a 4 channel amp, I get this problem when bridging the front channel to power the sub. If I bridge the rear channel I get a higher pitched noise but the same problem. If I only use the right or left side of either channel the noise is much quieter but still present.

I've been researching this site and it seems like the system's grounds are a common problem. I can trace the ground wire from the amp to the pass door then I lose it due to my fear of removing/breaking the plastic trim.

Does this sound like a ground issue and I need to start removing panels? Or is my amp bad and needs to be replaced(I don't have a spare amp to troubleshoot with).

Don't know if this helps but - the noise level is constant and unaffected by the hu volume control. Also, the sub is the only speaker receiving this ghost signal.

I'm pretty new at this stuff and would appreciate being pointed in the right direction! Thanks in advance

 

it does sound like a bad ground. the ground wire shouldnt be very long and straight from the amp to a point on the chassis. i would trace it to where they connected it. you may need to move it.

 

one other thing i forgot to mention. try disconnecting the inputs from the amp and see if it still hums. that way you can see if it's noise being added by the pac or the amp.

 

When I remove the inputs there is no hum.
Is there a common spot on the passenger side that installers use for the ground? I see all the wires going behind the panel that houses the rear speaker. Forward of that when I pull back the carpet behind the pass seat I can find all wires except for the ground. I would guess installers that do a lot of vette work(as mine does) would have a routine spot for the ground. Trying to avoid any extra tear down of the interior.
Thanks again

 

try hooking up an ipod or osmething like that directly to the amp via the rca cables and see what happens if you get noise or not. I suspect you have a blown ground on your pioneer radio which is a very common failure, even out of the box. The way to test this is behidn the radio connect a small wire from a screw (ground) on the radio and wrap it around the outter ring on the rca cable(s) running to the amp and see if the problem goes away. Let me know what happens

 

Before I start researching how to pull the deck to do this ground test, I have another question. The sound is fine through the front bose speakers, in fact it sounds pretty good just no bass as the amp is not connected right now. Is it possible for the hu to have a blown ground and still sound good through the front channel?

For the other test, the only headphone jack to rca cable I have is currently plugged into the back of the deck for the mp3 player. Can I test this with my home stereo's cd player?

 

You can use ur home cd player it prly wont be very loud but you can deff use it, it wont rule out the rca cable goin to the radio but odds are thats not the problem. Remeber the radio has to be on for the amp to actually turn on.

The bad ground would only effect whats hooked up to the rca output which would be the sub amp.

 

My pioneer had the ground go out. Why are they prone to that happening?

 

i guess ****ty build, the fix is to connect a wire from the ring on the rca to ground on the radio. they all are prone to it even the high end premiers. the only was to make sure it never happens is whenever you plug or unplug rca's unplug HU from wire harness

 

I'm surprised Pioneer doesn't fix that problem. When you pay a few hundred dollars for a HU, one would expect it to not have problems like that. Oh well.

 

Okay, I hooked up the cd player to the amp's rca inputs and the hum is still there, maybe even louder. Does this rule out the hu as a problem? I would think the problem would be either a bad ground or a bad amp.
If I were to run a new ground from the amp, where should I go with it? The amp is mounted on the back wall of the rear compartment. What size wire should I use, or can I test a new ground with any size? I'm sure I'll want a bigger size for a final fix, but to test can I use something smaller that I have laying around?

 

How are you doing this??? Are you running Rca's to the deck??? Are you running power wire and ground fromt he amp to the battery ( just the pos to the battery ) ground some where in the car.. I have done alot of installs in my time and from what i know.. IF ur running Rca's from the amp to the deck and a power lead. You need to make sure u run these on opposite sides of the car.. Say bring ur power wire along the drive side of the car and run ur rca's on the pass. side of the car.. This could be ur problem.. GOOD LUCK!!!

 

You can get away with 8 awg. power wire. Do not go any smaller then that.. Pull away ur carpet in the trunk area and find some metal.. Get some sand paper clean the paint away and self tap it there!!! I dont think ur amp would come on if ur ground wasnt good.

 

I didn't do the install, all the wires are on the pass side of the car. There is a power lead straight from the battery's power terminal, and there are rcas connecting the amp and deck. The ground from the amp runs to the front of the car, but I cannot find it forward of the panel that holds the rear pass speaker, I can find all other wires as they run down to the floorboard under the carpet behind the pass seat.

 

For what its worth, this setup was working good. Didn't want you to think this has been a problem from the start. That's why I think either a ground went bad or the amp went bad.

 

Who installed this????

This is a quick check... get another rca cord.. unplug from the deck and amp.. run and quick one on the opposite side of the car.. Also ur ground shouldnt be longer then 3 ft. But if all ur wires are together on one side. Id say thats an issue right there!!! Did this ever NOT hum???

 

Ahhhhhhhhhhh ok... If u know someone that has another amp.. any size.. hook it up and see what happens... I never heard of an amp going bad making humming noises.. bad ground maybe.. i would shorten ur ground wire personally. do u knwo what kinda rca's u used?? High end ones or cheap ones?? If they came from an audio shop they should be ok. maybe

 

not sure as to the brand of rcas, this install was done by a shop that is supposed to specialize in vette stereos and performance mods. Parking lot is usually full of vettes,vipers, ect. I've got to go to work, but I'll try the shorter ground wire later. Thanks for your time and help, I'll report back later!

 

Take it back to where u got it They should figure it out for you free of cost!!! IF all else fails!!!

 

I finally got a new, shorter ground wire hooked up, but it didn't solve the problem. I guess it's time to get a new amp. How about some suggestions around $200. All it needs to do is move the Fosgate P2 in the subthump box, won't be entering any competitions, just want a little extra bass.