Noise Coming Through Sound System

[PianoPlayer07]

Hi everyone,

So here's my situation. The past few weeks I have been adding on to my car stereo system. I've got a 1995 Jeep Grand Cherokee Limited with a Pioneer DEH-P3900MP head unit which I already had installed several years ago. What I added on was a Pioneer TS-W254R sub, a Boss AR2000M amp which powers the sub, a Boss R1004 amp which powers the door speakers, a SSL SX210 crossover, and a Absolute PD-150G power distribution block. I also used the Scosche 680W 8-Gauge wiring kit which should tell you what my main power and RCA cables are.

The problem is there is a whining sound that is coming through the system which I assume is alternator noise. I have searched through several threads and tried all of the usual tricks and made sure all of my T's were crossed and I's were dotted. My power cable is running from the positive terminal on my battery, through the fire wall and down the left side of the vehicle under the door trim to the back seats where the amps and stuff are. The RCA cables run from the head unit down the right side of the vehicle under the door trim and to the back seats. All power is run via the distribution block, I'm using the stock remote turn off wire which I assume shouldn't matter, and everything is grounded to the floor metal via their own cable. The head unit is grounded up front via another wire that runs down to the floor.

I've started at the amp trying to trace the source of the noise. I can unplug the RCA cables and the noise will disappear. I can take the main feed and plug it into the amp and it will make the noise. However, if I plug the crossover into the amp and don't plug the main feed into the crossover, there is no noise. I can also take my iPod and plug it directly into either the crossover or the amp and there is no noise, just a clear music signal. So I'm almost positive it's nothing back in that area. I think it must be something to do with the head unit. I can unplug the RCA cables from it and the noise will go away. I have also ruled out any noise being inserted through the RCA cables by plugging another set directly from the unit to the amp and the noise still exists. I've also ran a ground from the radio back to the ground post of the amps and the noise was actually worse than in the current ground spot. I've tried several grounding points and this one seems to be the best. I've even tried running a power wire directly from the head unit to the battery post with no luck.

I even tried grounded the RCA outputs by wrapping unshielded wire around the terminals and connecting the ends to a screw on the unit. Even wrapped bare wire around the outside edges of the cables themselves and grounded them with no luck. Didn't affect the noise at all.

Something that should be noted is that there was a stock ground wire that the head unit was hooked up to. The noise was MUCH louder when it was hooked up to this vs. the new ground wire that I ran. I can stick this same ground wire to the head unit and it will make the noise louder. I don't really understand this. Also the noise never changes when you adjust the volume on the unit. Things such as opening a door and making the dome lights come on, as well as turning the head lights on will cause a pop to come through the speakers as well.

I've attached a short MP3 of what the noise sounds like if that helps any. Please note that even though it is low quality due to how much I had to compress it to be able to upload it, all of the noise you hear is coming out of my speakers. Notice that it will change speed as the engine is revved up. To me it also sounds like there is two different frequencies. One a little lower that changes pitch when revving up the engine and one a little higher that always stays the same.

I feel like I've tried almost everything with no luck. Any suggestions? I'd like to avoid a filter if at all possible, but if that is my only option which one do I need? Also, buying a new head unit is out of the question as I've blown so much money on this already.

Sorry for such a long post but I'd appreciate any help at this point. Thanks!

Alternator Whine.zip

Click to read more...

 

[PianoPlayer07]

Anybody? I'm sitting here with a useless system right now. Please help.

 

[double 07 10+ year member]

Seems like I read somewhere that Pioneer head units have a fuse inside them for the RCAs that is prone to failing and allowing them to make this noise.....I would look for that inside deck.......It seems that almost every time one of these noise threads shows up its a Pioneer head unit being used!!!........good luck and I hope you figure it out

 

[PianoPlayer07]

Just an update:

Had a chance this morning to take the hu out of the front console and wired it up outside the vehicle and totally eliminated any factory harness warning. The hu was sitting on a table outside and I ran the power wire, turn off wire, and ground directly to the amp feeding my door speakers. I then used a short set of RCA cables hooked directly to that amp. What this also did was again, eliminate everything stock and allow everything in the chain to come to one power source and one ground source that I know is reliable.

The results were that the high pitched tone that had been coming through wasn't there anymore. However, the alternator sound was still coming through like it had been. I also tried wrapping unshielded wire around the outside of the RCA outputs again in an attempt to ground those but no difference was made.

My next move I think will be to hook the hu, one amp, and an external speaker up to another car's battery and fire up the engine. If the alternator noise is still there then I'll know it's for sure the hu. If it's not, then it will at least rule out equipment. I'm also going to try just soldering the pico fuse since that will for sure eliminate that issue. I have a suspicion that is the main culprit at this point.

I just want to re-illiterate once again that I have went through the chain and narrowed the problem down to the hu. I've hooked an iPod up and everything and the system operates fine using that. I've already tried most of the simple stuff, so please be sure to take a thorough look at my post before suggesting something I've already tried several times.

Thanks again.

 

[knightsdaze 10+ year member]

Pioneer head units are notorious for poor rca ground. There is a thread in here somewhere wher a guy shows very crudely, but effectively how to fix this problem. It worked like a charm for me on my DEH-P7200. Simply weave a few strands of 22 gauge wire, figure 8 style around the H.U. rca's and then ground them on a screw on the back of your H.U.'s chassis. when you push the cables on they pinch them in place.. like i said it's kind of a crude fix, but if your problem is poor rca H.U ground, this will do the trick.

 

[jasonAz 10+ year member]

Upgrade your power and ground wires to at least 4 awg. Did you try grounding everything(deck, crossover, amps) to the same ground? Is your ground a good ground on sheet metal(not a bolt). Do what knightsdaze said!

 

[BumpinBabe 10+ year member]

I ended up having to disconnect my second amp and my 6X9s because of this very issue. Are the RCA outputs you're using embedded in the head unit, or do they leave the back of the head unit as two wires with female parts on the end? It was only my second set that caused any noise interference, not the first set that is built in to the deck.

 

[PianoPlayer07]

Bought a new deck and installed it this morning. Guess what...STILL HAS NOISE!!! I had a friend who has worked with electronics for many years to check the grounds. The ground for the amps in the back was perfect as well as the new ground that I ran for the hu in front. Oddly enough the stock ground wire that I was using at the hu had a little voltage coming through it and would fluctuate when say you opened a door or something. He also checked the pico fuse in my other hu and it was fine. We tried several things including hooking the ground up to the negative battery post which actually made the problem worse. We also tried eliminating everything used in the stock wiring harness by hooking power, ground, and turn off all in the back. Nothing was coming from the stock wiring except the speaker wires which goes to the doors. The noise still came through.

Here's the kicker. We also tried hooking everything up outside by using the hu, one amp, and an external set of speakers. We just ran power and ground directly off of the battery posts. No noise using this method.

After buying a new unit and still having the problem I am at a loss of ideas at this point. Maybe noise is being inserted through the speaker wires? If this was the case why has it never done it up until this point?

Please help!

 

[PianoPlayer07]

I've had a few say I've got the input gains on the amp set up wrong. Regarding input gains on the amps, they can be all the way down with the gain on the radio about 3/4 of the way turned up and the noise is still audible enough to bother you. Believe me, I know the importance of gain structure since I am a musician and am around all kinds of audio equipment all the time.

I did pick up a power filter and put it on both the constant and accessory power feeds (They only had one, will pick up another when available) and the alternator noise was removed to the point to where you would really have to be listening for it to notice. Just to verify, do I need one for the turn on wire as well or just the two power feeds? Anyways that should take care of that problem. It did NOT however affect the high pitched tone that comes through. If you'll remember I said it will not come through when I have all connections on the radio hooked up where the amps are as well as running everything off of the battery. It only happens when the unit is hooked up front in the console. What I did to find the source was I unhooked everything from the hu except the RCA cables running to the amps and the ground wire. No power connections were connected. The hu was obviously turned off since no power was connected. This high pitched tone was coming through. I could disconnect the ground wire and all noise would disappear. The noise would return by hooking the ground back up. That leads me to believe the source of this sound is through the ground wire. Even though the ground point seemed to check out as being alright and I'm using a heavier gauge wire, it must be picking up interference along the wire run somehow. I'll try grounding the hu somewhere in the back where the amps are grounded.

I hope this is a good sign, working towards a noise free system. Does my above thinking seem to be correct? Or do I need to do something different? Again, this is certainly not a gain structure issue. I'm very familiar with how to set all of that up.

 

[jasonAz 10+ year member]

the audio clip, sounds like its just a constant whine, not an alternator whine. If all the grounds are good and to a solid piece of sheet metal, not a bolt then how close are you to a fuel pump? Does the whine happen when the key is in the on position and the car is NOT running as well as when the car is running?