Drudis

I noticed a high pitched whine recently that is apparently so common in these cars. It occurs when the volume is above 0 - via all input sources, even during use of the HFL function. I did some digging on here and found many, many similar issues, but they all seemed to have subtle differences - and none that I could find mentioned the noise being present through all sources - radio, tape, xm, HFL. I do have some aftermarket equipment:

iSimple Gateway ishd571
Kenwood 8105d (2)
Audiobahn aw1200q (2)

The noise started a couple years after installation. When the noise first started, it was only present during the use of iSimple - then when I replaced my first failed (iSimple phone connection) cable, the noise was gone. Now it's back through all stereo sources. Is this more likely to be coming from the HU ground? Factory amp ground? iSimple ground? How can I check these?

I checked my aftermarket amps' groundwire, and it appeared to be fine.

kTunedHFPNYC

iTrader: (1)

Where are you grounding the kenwoods and audiobahns?
Are you using an LOC?
Can you unplug 12V from the iSimple and see if it goes away, sicne yu think its the iSimple.

To check grounds, you would check resistance from what I understand.
And you want it to be <0.5ohm, from what I understand, but I don't know much about using my handy dandy digital multimeter (DMM).

I used to have the KAC-8105D too, and it wasn't the cleanest power.
Have you tried adjusting gains a little lower, all across the board?
Post some pictures of your grounds, from the battery, to all your amps.
Preferably, all amps should be grounded in one place, if possible, or at least, same lateral piece of sheet metal.

Alternator whine is a high-pitched whine that changes with RPM input.
So when you drive does the loudness/frequency of the whine change?
If it doesn't then it's not alternator whine.
You might mean a hiss, I have a hiss too

Drudis

The Kenwood amps are grounded on the trunk lid (same ground for both - on the driver side). I am using an LOC - it's coming from the factory sub wire. I'll check the iSimple wiring - hopefully it will be simple to pinpoint (i.e. red +, black -). I'll try to get some pics while I'm at it.

Gains aren't likely to solve the issue since they have been at the same level the whole time. I'll check the iSimple wiring and RCAs first.

It's definitely alternator whine - it changes in pitch with acceleration. I've also noticed that it seems a tad bit worse in really cold weather.

I just had the alternator and battery checked, both are fine - so that's not the issue.

Squashy

So you have an amp in this car? How many? I get hiss through the exact isimple you have but only on aux source when units unplugged. If your getting alternator whine it can be for a few reasons.

1. If amplified the quality of the amps used
2. If amplified where the power wire was ran in comparisosm to where the rca(single cables) are ran if they are both running down the same side of the car it will easily pick up that interference.
3. Direct current flows from ground to positive so when possible you want a stronger fauge ground than power, amd as someone mentioned what do your ground locations look like send pics.

Id advise you. to follow ktunes advice disconnect isimple completely see if theres a change. Alternator whine is hard to troubleshoot and or eliminate due to cheaper amps arent built as well and can naturally have it. If your power amd rcsa are ran on same side run the rcas along the opposite side.

You can always try ground loop isolators, or better line out convertors, theres a lot of parts in your system and 1 or all of them can be contributing to it.

Let me know any other questions

QuickTL07

Kenwoods are knows for bad grounds, you need to have a solid ground, i cant stress that enough of any car audio build, that wire that goes from battery to the body of the car is to small to began with!
Have you isolated your power wire that goes all the way to the trunk.. there is so much shit that could go down with ground noise... from alternator wine, to other crap....
Also it could be bad RCA, or something in these lines.... there is to many possibilities that could go wrong or are bad at the same time.