Radio noise aftermarket HU install
 

Installed a Alpine ilx-w650 HU in my 2009 Z06. While the vehicle is running there is a high pitched whine if the volume is at 1 or higher. It doesnt get louder if the volume is increased. It also goes away if the volume is at 0 or if the car is in accessory mode (radio on but engine off) I tried searching the forum but couldn't find the exact symptoms. Anybody have this issue and resolved it? Thanks

It's almost certainly a ground issue. I had never had one in previous stereos I've installed, but had a BAD alternator whine when I finished the Vette install. I went back and added a 4 gauge wire to tie the chassis ground for the amps back to the battery and regrounded the head unit, my shift light, and my valentine bluetooth unit. It's much better, but I still think there is a slight whine I need to track down.

Yep. Alternator whine. This is caused by a speaker or signal wire being too close to a power wire, or a bad (too small) ground.

Check that your RCA plugs are plugged in all the way. I just finished an install and experienced this. RCA plug came partially unplugged. If connections are ok and you still have noise, disconnect the rca plugs from the amp and with car running, see if you have whine. If so it is the amp ground. I would bet it is amp related if it does not increase and deceease with the volume control.

Thanks for the responses fellas. I ended up installing a ground loop isolator and that took care of 95% of the noise with no noticeable difference in volume. Had to get my car back together. Ill chase the other 5% later.

I finally fixed the exact same issue this past weekend in my 07 Z06. After working through all the troubleshooting steps it turned out to be the HU ground, which was odd because I never noticed it before I added an amp and replaced all the speakers (maybe the factory amp masked it?). Since the amp is grounded to the factory location behind the passenger seat and didn't introduce any noise, I ended up running a separate ground for the HU to the factory location behind the drivers seat. Now there's 0 noise in the system.

Hope this helps.

Good job!

Thanks Mecha. I should have some time to open everything back up this weekend. Hopefully can get it to 0 noise as well.

Never use ground loop isolators, they don't fix the problem, they just mask it. Take the time to trouble shoot the problem, and fix it right

Madsonp I hear ya about making the problem. I just didnt have the time to chase the grounds when installing the radio. I needed to get the car back together at the time and that whining noise wouldve drove me crazy. Ill have some time this weekend to get it figured out. Thanks for the input

I have faith in you brother. :thumbs:

No luck tracking the whine today. Heres everything I tried.

Disconnected HU ground. No change
Removed ground behind passenger seat and removed all paint.
Ran ground from HU to seat location. NC
Ran ground from factory amp to seat location. NC
Ran ground from HU to neg. battery. Increased noise
Reinstalled the factory HU sound is gone.

Should I be using the low or high level inputs. Currently using the rca inputs.

Im using a Pac rp4 gm11 that was recommended. It doesnt retain onstar but I didnt care. Should I have went with the rp5 instead? Could that be the source of the noise?

You guys have any other ideas?

I agree that it's better to avoid the ground loops in the first place, but I disagree about the ground loop isolators. They do break the loops and prevent ground loop currents from flowing.

As illustrated in the diagram below, a ground loop could be formed when a headunit and an amp are grounded to the car chassis at different points (for example, A and B). If the difference of potential between those 2 points is enough, a ground loop current will flow through the interconnect's shielding, using the car chassis to close its circuit.

https://cimg6.ibsrv.net/gimg/www.cor...20f695fd04.jpg

A ground loop isolator effectively breaks this loop, and no ground loop current will flow:

https://cimg7.ibsrv.net/gimg/www.cor...18bbdcd7a6.jpg

That being said, a transformer generally introduces some distortion in frequency response. An isolator designed specifically for the relevant frequency range must be used, and it should be magnetically shielded, in addition to have a Faraday shield between its windings. Quality is important here, but this shouldn't be a problem with a Jensen Iso-Max for example:

https://cimg5.ibsrv.net/gimg/www.cor...43309c0cf0.jpg


As you just did, single-point grounding of all devices, as close as possible to the amp (the device that draws the higher current), using proper gauge wires is the recommended way to do this, although you reported no change.


This just increased the difference of potential between the ground points, which made things worse as expected.


Sometimes a given combination of cabling and equipment interaction can cause ground loops to occur in one scenario but not another.

Perhaps the noise is being induced, that's why it's important to use high quality, full shielding cables, and avoid running them near/along power wires.

Another possibility is that the noise might be coming from the alternator through the power feed. You could try inserting a 1mH/10A inductor right before the power feed enters the headunit to block the noise. If needed you can do the same in the amp, using a 1mH @ double the current the amp is rated.


I always use low level connections whenever possible.

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