Help! Alternator Whine

I'm not sure where to go with this anymore, I have a single 10" Alpine sub with a cheap amp and that works great. For mids and highs i'm using 6.5" Polk audio components, I used to have them amp, but assumed my amp was fried when it shorted out and had a crazy amount of alternator whine. I just bought an Eclipse EA4000 amp and it too has a CRAZY amount of alternator whine. When just running off of the headunit i do not get any whine at all, why am I getting it with amps ? They are properly grounded, I've recently replaced the alternator, new battery ends and the RCAs are run along the opposing side of the Jeep from the power wire. I tried switched the front and rear RCAs hoping it was maybe a bad RCA wire but no dice. I'm not sure where else to go with this. I really need help, or suggestions.

It is called a ground loop. This is caused by the difference in potential between grounds ( ie: you have a bad ground somewhere). Try locating all the grounds from all stereo equipment into one spot. If this doesn't work or you just don't want to do the labor go to the nearest audio store and ask for a GLI (ground loop isolator), should cost between $15 and $40 according to quality. This installs onto the RCA cable of the offending amplifier. If your amplifier is really cheap the ground loop is probably inside the amplifier.

I located the ground for the headunit and both amps to one common point and it fixed nothing. I also bought 2 ground loop isolators and it changed nothing when hooked up to the 4 channel and when hooked up to the sub amp it cuts 90% of the subs volume out.

Check your grounds - make sure the contact patches are clean. Check all of the grounds you can find - the mains (chassis and engine,) the engine-to-chassis ground, the various signal/sensor grounds in the engine bay (should be at/near the dipstick tube mounting bracket and the driver's side fender liner,) and even the rear lighting ground (behind the driver's side trim liner.)

Clean the patches down to bare metal and apply corrosion inhibitor. Clean the lugs. Replace the screws (if dirty.)

Look for an RFI cap that goes on the back of your alternator - between the output stud and the case. This also helps to fill in the ripples in output voltage (which is what you're hearing as a "whine,") to stabilise the output. These were common in the 1970's and early 1980's as original equipment, in order to keep alternator whine from interfering with early electronic controls (before rectifiers improved, and noise deadeners were installed into controller inputs - or the circuits got better able to not consider the noise as part of the signal.)

I've also found it helpful from time to time to "choke" speaker leads - get a powdered iron toroid core (looks like an iron doughnut,) and wrap 3-6 turns of speaker wire around it just before it gets to the speaker. You'll have to experiment a bit to get it spot-on, but I've done this to eliminate 60Hz AC hum (in household applications) and alternator ripple hum (in automotive.) You just have to play about with it, since each application is a bit different.

I've checked all the grounds, i've even connected the grounds of the amps and headunit RIGHT to the battery. I'm starting to suspect a bad Headunit or amp. However, since the volume of the radio doesn't affect the volume of the whine, but rather the gain on the amp does. But wait, I had a friend run an rca from the back of his radio to the input on my amp and there was no noise at all, maybe the headunit is to blame ?

stop what your doing buy all this non sense.

1. Are your rca cables separate from your power wire? If there not, then separate them.
2. I had the whine until I grounded the rca's from the head unit its self.


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

THANK YOU! I'm going to give that a shot today. The power wire is run on the passenger side, and my RCAs are on the drivers side, along with the Remote wire and a power wire for my AUX reverse lights. I think I'll move those over to the passenger side at the same time.

That fixed everything, thank you man.