After much trial and tribulation, perhaps to be detailed later, my system is installed in my 06 coupe. I now have alternator whine - high pitched, increases in frequency along with engine RPM, fixed volume.

Amplifier power and ground cables run along the far right side of the car. The amp is grounded on the bolt beside the passenger seat. Speaker cable for the front right runs along the right side of the transmission hump, underneath the parking break, then underheath the dash into the door. Amp remote lead runs straight down the top of the hump. RCA cables run along the left side of the hump. Speaker cable for the front left runs along the far left of the car. Rear speaker cables run straight back, then turn toward the center to the amp location. So, the power and signal cables should be far enough apart that the signal cables aren't picking up interference.

When I unplug the RCA cables from the amp, the noise stops. Looks like I have a ground loop. I moved the head unit ground from the wiring harness to a grounded bolt behind the console, and the noise is still there.

My options at this point appear to be

A) Move the head unit ground to the same site as the amp ground.

B) Use ground loop isolators on the RCA cables.

Would isolators have any negative effect on sound quality?

Edit: I should add that I tried unplugging everything else from the back of the head unit (antenna, aux input, etc.) and that had no effect on the whine. It's definitely coming through the RCAs.

 

have you tried grounding negative side of rca cables to the chassis of the head unit?

 

I haven't tried that, but I will after work. If grounding the RCA to the head unit chassis silences the whine, how do I fix it permanently? If it doesn't help, what's the next step?

 

That is how you fix it permanently.

The GLI's would also work. IMO you can't tell when they're installed, but some claim they can hear a difference.

 

I ended up using ground loop isolators in my setup and the noise is completely gone. I did notice a slight drop in sound level and turning the gain up on the amps a bit got it back to sounding normal. Also the instructions say to put them on the RCA's behind the HU. I didn't feel like pulling the console apart again so I first tried putting them at the amp end of the RCA's and it worked fine.

 

curious what amp? is it a pdx by chance

 

Yes, as a matter of fact, it is a PDX5. I grounded the front and rear RCAs to screws on the back of the head unit, and the whine is gone. Thanks, guys!

Is there something specific to the PDX I can do to further reduce noise?

 

no but i sware of all the amps i install (which is alot) i have nothing but issues with PDX amps and whine especially in fiberglass cars

 

The PDX5 was my first choice, but I initially went with an Infinity Kappa Five because of the price difference. After 14 hours of work on Saturday, taking things apart, putting down BXT and Ensolite, running cable, reassembling, I was ready to start the system. I got 3 seconds of music from the Kappa before it started exploding. The amp itself was popping, crackling, and smoking, and a godawful whine was coming from the speakers. I shut off the head unit and accessory power, but the amp kept exploding until I pulled the inline fuse next to the battery.

The inline fuse (80 amp, just like the manual for the Kappa specified) was a little warm, but intact. Neither of the two 40 amp fuses in the Kappa tripped. I checked amp power and ground with a multimeter and got 12.14V at 0 Ohm. The wiring is fine, the amp is just defective. I found a local shop open on Sunday and picked up the PDX5, which works fine without changing the wiring.

Now that I have the alternator whine licked, the system sounds awesome. The head unit is a Pioneer FH-P8000BT, which I actually find a little disappointing since the crossover and EQ settings aren't nearly as extensive as on my 5 year old DEH-P720. The doors have Polk MM 6501 components, and MM 521 coaxials are in the back. Subs are 2 MM 1040s. The speakers are really bright with the PDX (even with the 6501 x-overs set to -3 for the tweeters), but tamed with EQ on the head unit. The bass hits HARD, and everything between has excellent detail.

I went for a drive with the top off after grounding the RCAs, and I couldn't stop grinning

 

Just an FYI, the whine is generally caused when you put the power on the same side of the car as the RCA cables.

Power cable should go down the side where the battery is, the RCA cables go on the opposite side of the car.

I had the whine on my first two installs, then i talked to an audio installer guy and while he went into a lot of detail, the above is essentially what it boiled down too.

He also told me to make sure that when i ground to the car, that i make sure to ground to an unpainted part of the chasis(scrape paint if necessary).

 

Although the RCAs running alongside the power can often(usually) add some noise to the system, a ground loop is a ground loop. Grounding all components to a common ground is usually the best way to ensure no noise. After many (many) years of installing, I only ever used ground loop isolators twice that I can remember. One if those was a weird install with 6 amps, 2 source units, a stalk mount and trunk mount EQ, and misc electronic crossovers.

I just finished up the instal in my C6. Thought I could get away with connecting the HU to the stock harness, since all the rest of the wiring (and wires) were perfect. Sure enough, the whine was there. Grounding the RCAs didn't help. But the moment I ran the HU ground to my ground bar, it's completely gone.

 

I hope I'm not jacking the thread, but this is another alternator whine issue. I just installed a Sony XNV-770BT in my '11 GS and had a bad alternator whine. I'm using an OS2C to the stock harness and speakers. I installed GLI's and used a different ground from the stock harness and got rid of most of it except for a very low level whine from the rear speakers. I also grounded the RCA's. When I switch on OnStar the whine is really bad. Any thoughts on why I'm still getting a low level whine on the rear speakers and why OnStar is so much worse?

At what point should I look at a filter between the alternator and the battery and what kind should I get if I go that route?

Thanks.

 

Before you do anything at the alternator, try using one of THESE between the oem car harness and the constant supply to the radio.