High Pitch Background Noise

[sierra4x4 10+ year member]

I just installed my first audio system, with the help of a friend with a few years experience with car audio. This is my setup (in a 2004 GMC Sierra):

-Pioneer Premier P690UB HU

-ZedAudio Gladius powering Rainbow SLC 265 Components

-ZedAudio Minilith powering TC 10 OEM Sub

Now I am getting a constant high pitch tone from the tweeters. It reminds me of the occasional tone you hear from a TV or computer, but with a little more of a static buzz to it. The noise never changes volume or pitch, and is present when the ignition is in ACC. So that rules out Alternator Whine.

Even if it is a myth, I kept good distance between all the signal wires and the power wires. And my amps and HU are all grounded to the same point, so I think that rules out a ground loop. I sanded down to clean, shiny, bare metal for the ground.

I have read all about the infamous Pioneer grounding problem, and I have tried the solution. I coiled wire around the "barrels" of the preouts and grounded them to the "chassis" of the HU. That didn't help.

The noise goes away when I unplug the RCAs from the back of the Gladius. So I think the problem is upstream from the amp. That only leaves about 20ft of RCA and the HU. Is it possible I have a bad HU, or is there something I am missing? Everything sound great, but whenever there is a quiet point in the music, I can;t help but be annoyed by the buzz. Any suggestions would be greatly appreciated.

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[mlstrass 5,000+ posts]

Have you tried swapping the RCA yet?

 

[AwaySooner 10+ year member]

I have similar problem with my Gladius, why don't you try this. If your headunit has HPF, use it. Then set the Gladius to Normal Mode and Filter to Flat, or set the Mode to DIRECT to by pass the HPF. See if you still getting noise? If you have Burr Brown upgrade, DIRECT would be fine and still has the opamp in the circuitry. I confirmed that with Steve.

 

[sierra4x4 10+ year member]

Thanks for the replies guys.

-To mlstrass: do you mean running different RCAs from the headunit to the amp?

-To AwaySooner: now that you mention it, a wierd thing did happen with changing the amp settings. When I first fired up the system with just the components running(I hadn't wired up the sub yet, though I did have the minilith ready to go), I heard the buzz in the tweeters.

I started fooling with the amp settings and was able to eliminate the noise by doing exactly what you said. It went away when the Gladius was in "normal" with the filter on "Flat" and it also went away with mode on "Direct." That was during my test runs. After getting everything hooked up and running, the buzz came back. I thought the sub might have had something to do with it, but I still hear it even with the sub outputs turned off at the HU.

 

[synikalt 10+ year member]

You know what...the same thing happen to me sierra4x. I was re-running wires more separated from eachother becuase the power and rcas were a tad bit too close..then i turn on the amp for my front stage to tune it agian, and i messed with settings to "FLAT-Lp-HP" i went straight to flat and others to HP just and playing with gains yet i never heard distortion..and i tuned itt o ear how i liked it..then i turn car off..and was setting my amp for sub woofer on..then i get LOUD ENGINE whine..and it took me 5 hours to try to correct the problem..still got it..and infact my amp just stays in "CLIP-Protect"...i still have to correct this problem. idk if i may have blew it

 

[AwaySooner 10+ year member]

The sub-output on HU turn to off does not eliminating the sub-amp from the system. Can you just removethe sub amp fuse all together? Or use a muting plugs to the sub-amp. They do fuse separately right?

Sometimes the gain is just too high, try reset the gain with the HU SLA set to highest (I don't listen to radio, my CD Changer is +2, HU CD player +3 and XM is +4) and turn the volume higher, my pioneer unit AVIC-D3 doesn't distort even up to 35/40. This way you can turn down the gain on the amps.

 

[sierra4x4 10+ year member]

The gains are already below 50% on both the gladius and the minilith, but I will try adjusting the SLA and resetting the gains.

 

[sierra4x4 10+ year member]

Resetting the gains didn't get me anywhere.

I thought that grounding everything to the same spot was the next best thing to grounding to the battery for avoiding ground loops. But, could grounding the HU to the same place as the amps be creating feedback that would result in the noise?

 

[AwaySooner 10+ year member]

Did you run a very long ground wire from the HU just for the sake of having the same ground point as the amp? No harm trying just ground the HU at a good spot behind the dash and keep it short.

 

[sierra4x4 10+ year member]

Thanks for the suggestions AwaySooner. I guess the ground wire is probably around 10-12ft long (18 gauge I think). I am about to start pulling things apart though, and I will try that.

BTW, does anybody know if this constant high tone could damage the tweeters?

 

[goodstuff 10+ year member]

Try grounding the deck as suggested above, just be sure you are grounding to metal and not plastic inside the dash....but you seem to have a solid understanding of making a good ground.

 

[SRim23 5,000+ posts]

try some of these. i hear grounding rca's to the HU has helped many

http://www.caraudio.com/forum/showthread.php?t=198477

 

[AK SloPok 10+ year member]

How are you amps grounded? I have an 05 Silverado and it was a pain to get a good ground. May try running a large dia cable directly to the frame if you are grounding to the body.

 

[sierra4x4 10+ year member]

Right now my amps are grounded to the same spot: a bolt through the body about 2 inches away from one of the bench seat bolts. They are each grounded with 8 gauge wire, with no more than a foot of length. The radio ground is on the same bolt, on top of the other two wires.

 

[sierra4x4 10+ year member]

Wow, I feel retarded. I swapped the RCAs, and presto, no noise. I was running shielded Knukonceptz RCAs from the HU to the Gladius(for the components). I switched them with the twisted RCAs I had running from the HU to the Minilith(for the sub). After that 5-minute procedure: no noise and everything runs fine. I guess I should have tried mlstrass's suggestion earlier, but I thought the shielding would be enough. I didn't think "fancy" cables would make much of a difference for anything outside of the competition circuit, but I am definitely a believer now.