Help with Sound Gremlins

Guys & Gals, I need some serious help...

Here is the story: My system has had terrible alternator whine since it was installed by the shop... it actually seemed to get worse as of late to the point I couldn't stand it anymore... if there is that much whine I better have a supercharger! Anyways, I decided to upgrade and fix the system once and for all.

I pulled the entire interior of the truck, installed 2 layers of Fatmat Xtreme, upgraded to 2 AWG power cable (down driver's side) with a 125A ANL fuse in the engine bay and a AGX(i think) at the distro block on the box in the back. I replaced el-cheapo RCAs with Monster MPC I404s (I know many people hate Monster and think they are overpriced, but I got a good price on them and they are tripple shielded). I upgraded the grounds to 4GA from the amps to a distro block and 2 AWG from the block to a bolt behind the rear-driver's side seat and a short jump to the seat bolt. They were sanded down beforehand.

I buttoned everything back up and the alternator whine is GONE! Way to go me... but now there is a constant high frequency tone in the system that is unbearable! I can't stand to have the stereo on. It is not there with the 1st click of the key, 2nd click it comes on, truck running it is there! Also, with the volume at 0 I can still hear it (it is completely volume/source independent and still makes it with the RCAs undone at the HU). Also volume at 0 there is leakage into the rear speakers of the source (think this is gain related?).

I ran some OLD radioshack gold RCAs down the middle of the truck over the seats and it sounds good; there is no whine and no white noise in the line. The 404s are on the passenger side. There is some major EMI/RFI getting into my signal. It seems to make AM radio noises as you move the cable a bit (old school style as you run the dial through the AM band but not that pronounced.). I pulled the 404 out of the track and the signal got much cleaner, but the noise is still there at unacceptable levels. It gets MUCH worse if I touch the cable to the seat belt reel on the rear-passenger side (painful levels). I tried running a temporary ground from the amps to a few spots with no change in the noise.

HU: Kenwood DNX5120
Speakers: Focal Polyglass 165 CVX + 165VBs
Subs: RE Audio SX
Amp: Treo Engineering SSX 40.4

Please help!

 

When you ran the RCA and the power cables did you run them on opposite sides of the truck or on the same side? From my experiences, most of the time the whine is just electric interference coming in thru the RCA cables.

 

power is driver's side, RCAs are passenger side. they never cross/touch

 

Sounds like you may have ran a screw thru the RCA cable or somehow shorted it to the chassis. Good luck finding it. If you have a single RCA cable, you could find out which one is shorted by subbing it in for each left & right for each channel.

 

Keep your RCA's plugged in at the HU and unplug them from the amp. Then turn on the system. Does it still make the sound? That will tell you if Stu is right about a short in the RCA's somewhere on their way back to the amp.



If the noise is still there at the amp then you might have a different problem. It's way more complicated so try out that first test I listed and if you still have the noise then we'll talk about action two.

 

unplugged them at the amp and it 80% cleared, but was definitely still there. I checked again, the level of noise increases dramatically when the RCA gets close to that seat belt reel.
I tried unplugging them at the amp one at a time too. Noticed the the left side of the truck is better than the right... and that the right rear seems to be causing most of the noise.

This is my second set of RCAs. Isn't it unlikely that I got a bad cable from M*nster? I am trying ot avoid completely pulling the cables and laying them across the seats if I can since that involves pulling interior panels... again .

 

K, so with your extra RCA cable, unplug the right-rear RCA from both the HU & the amp & replace with just one color (the red connectors) of the extra cables. If that fixes it, you have a "leak" or you're shorting to chassis. with that right-rear cable. Inspect it & you may get away with wrapping some electrical tape around it. I'd replace it totally, if'n it was me.

 

ok. I will give it a go after I get my dinner off of the stove. I will let you know soon. Thanks for the help so far.

 

There should be no issue with the RCA's being on the opposite side of the vehicle. Physics nor my life experiences support noise being caused by the power wire inducing noise into the signal. If moving them fixes the issue, then the issue was with something else that corrected during your moving of wires.

Anyway, I agree that you should try turning the system on with the RCAs disconnected to see if the noises are induced through the source or through the amps. If it is from the HU, a faulty ground may be the cause. I'd avoid using the stock grounding wire and connect to something a bit more substantial behind the dash.

 

tried having just the right rear ch disconnected from the HU and amp... noise was much more pronounced. I am ready to rip the whole system out of the truck and burn it to the ground.

 

Listen to Sooner. It is likely your ground wire, and possibly behind the HU. Did you check that your connections on your wire harness are all soldered and shielded well?

 

Afirm. The grounds behind the HU are good. I just re -soldered them all last night.

 

Is your amp grounded to the seat belt bolt?

 

grounded serially 1st to a bolt in the floor of the truck my the rear-left body mount and 2nd to a seat belt bolt.

 

Have you used a volt meter to confirm your grounds are solid? You are getting electrical interference in your signal but I promise it has nothing to do with running lines parallel (like sooner said). That is a myth.

Is it possible your RCA wires were damaged during install and the ground is feeding back into that signal?

 

I will take the voltmeter to my grounds tomorrow after work and check them all again. I will also see about returning the 404s and getting a new set of cables. I'm done for the night...

 

This wont matter since he tested it without any RCA's plugged in. That test was to see if the signal was being sent from the headunit. Since it made the noise even while the RCA's were unplugged it's likely something else.

This sounds like a problem. Why on earth do you have more than one ground? I think you have a ground loop. Ground both items to the exact same bolt.

 

Yep, re-read through it. While I'd still suggest grounding the HU to something more substantial than the factory harness, this is more preventative than anything else. Besides, it would fit in well with your power/ground wire over kill.

From some of the other descriptions, it does seem like it is a faulty RCA. My guess would be that it was somehow pinched when the trim panels were put back on or something wore through / chewed through the shielding. While this may be a PITA, pop those trim pieces and inspect.

A good source for new RCA's is www.knukonceptz.com He sells good quality stuff at a fairly reasonable price. Cheesy name, but great wiring and cable products for car or home without a rediculous price tag.

 

They are only a couple of inches apart and I wanted to make sure that I had a good mechanical ground and electrical ground. Both were sanded 1st. I read that the seat belt bolts didn't work well. I will check to see if there is a resistance/potential between them.

Overkill... that is a good name for my truck. Is that steel crosstube in the dash a good source if it is drilled and tapped for a screw?

I ripped it apart last night and pulled the RCAs. They are definately a contributing factor. I will repace those and already contacted the store I bought them from for an RMA.... fingers crossed. That was expensive.

Thanks for the link. Those look like good products with terrible names. Prices are cheap too.

Hopefully tonight when I am rechecking all of the grounds I find a gremlin and with the new cables can put this to rest. I have so much $ tied up in a system that I can't stand to have on!

Thanks for all of the help everyone. I will post more tonight when I get home.

 

I have used knukonceptz wiring for home and car for 10 years and not had an issue with anything. The one time I had an order messed up, he left out a distrobution block and some fuses, he overnighted them to me and sent me some extra speaker wire for the delay. He has always been pretty good guy.