I've had alternator whine in my system ever since it was installed, and I've just ignored it until now.

Alpine 9857 Head Unit - Plugged into the back of it is:

1) 2 Sets of RCAs - Going to Audiobahn 4ch amp which powers the mids, RCA pass thru on that to the 2ch Subwoofer Amp
2) Full Speed iPod connection
3) Sirius Radio - SC1 Antenna --> Sirius Tuner --> KCA-SC100 adapter box --> Alpine HU
4) Radio Antenna
5) Main Wiring Harness

Mids: 5.25 components in the front, with crossovers, can't remember the brand at the moment. 6.5 Pioneers in the back. 12" Infinity Perfect subwoofer.

So the first thing I do is disconnect RCAs going to the amps, alternator whine still there. I plug them back in. Then I check the speaker wires on the Audiobahn for a short to ground (to both sets of mids), and what do you know each speaker wire (+ and -) is basically shorted to ground (6-8 ohms or less). Disconnect the RCAs and the speaker wires are fine. Check the RCAs coming from the HU, and the shielding on each RCA wire is shorted to ground.

So I pull out the head unit, disconnect everything. From here on out, everything I'm doing is trying to do is to try and see what causes the RCA jacks to short to ground. When I plug in the main wiring harness, the jacks are fine, but here's where it gets weird. Whenever I plug in ANY accessory, on its own, into the head unit (Sirius, iPod, radio antenna) the RCA jacks are shorted to ground. I check the shielding of the radio antenna and of course it's shorted to ground, but the whine is still present with the antenna disconnected so that's not it. In fact I *think* the whine was still there to some degree with just the wiring harness and RCAs connected (but I can verity this if its crucial). Its just flipping weird...especially for the iPod. The iPod cable isn't connected to anything except the iPod, so I don't see how it makes the RCA jacks go to ground. I also unplugged everything going into the HU, and checked for whine and there was none (I guess that can happen with power/signal crosses).

The head unit is grounded well, I've changed the HU ground location 2 times trying to fix this but to no avail.

Any ideas on what I need to check here? I'm out of ideas at the moment.

If I decide to be a quitter where should I take this to have someone look at it? If one of you guys is up for the challenge let me know. I can come to you, and I have $ if you can fix it.

3/11/2008 8:18:56 AM

sounds as if you've got an internal short somewhere. if the ipod is only connected to the HU, and plugging it in causes the preouts to drop to ground (and it does the same with all the other accessories), it's something inside the HU.

also - do the terminals on the harness work OK with accessories connected? does it just do it on the preout to the 4ch amp?

3/11/2008 8:28:33 AM

Quote :

"sounds as if you've got an internal short somewhere. if the ipod is only connected to the HU, and plugging it in causes the RCAs to drop to ground (and it does the same with all the other accessories), it's something inside the H"

grr that thing it pretty new, but of course i bought it off eBay so warranty=null

Quote :

"are the components driven by the 4ch amp or the HU's internal amp via the harness? do the terminals on the harness work OK with accessories connected?"

I'm not using the internal amp at all. (In fact I think I can turn it off, though I doubt that will fix anything.) All mids are driven by the Audiobahn. Terminals on the harness? You mean the speaker wires on the main harness (that i'm not using), or some of the other wires. What do you mean do they "work?" Are you asking if they short to ground when I hook up accessories?

3/11/2008 8:31:44 AM

too many words, but this worked in my case:


powering the ipod from my armrest ciggy lighter was the cause of my ground loop, so i stuck a GLI between the line out of the ipod and the line in of the stereo. It's not ideal since a GLI kinda messes with your sound, but it worked for me.

if you've already determined it's not the ipod, then i would suggest rerouting your rca/harness cables. In my car there are 'black boxes' (airbag sensors and the likes) that cause massive interference. They're all cleverly located right underneath the factory stereo. So I had to route my harness in from the side to get rid of whine.

[Edited on March 11, 2008 at 8:37 AM. Reason : d]

3/11/2008 8:35:55 AM

so you're driving the crossovers on the components from the audiobahn amp as well as the 6.5s in the back?

sorry if i sound retarded, i didn't get much sleep last night and it's early

if you hook up a spare speaker to one of the speaker terminals in the main harness, is the wine still there w/ accessories plugged in?

i.e. is it only coming out of the preouts

^the cable he's got powers the ipod via the HU

^good suggestion... try just running a new set of RCAs straight from the preouts to the inputs on the 4ch amp and don't hide the wire... see if it goes away (although if it's a true ground loop, i don't think this would be the cause)

3/11/2008 8:36:00 AM

also, at least on the sirius box, make sure you're grabbing its power from the same lead as the HU. might even be worth bolting down 1 negative terminal and getting a distro block to run all the negative leads to stuff.

you could also try grounding the barrel of one of the preouts to some metal on the head unit - a lead could have gotten cut internally or something.

[Edited on March 11, 2008 at 8:47 AM. Reason : you should go find a decent multimeter]

3/11/2008 8:47:32 AM

oh one other important note.

I can only hear the whine coming from the front left tweeter (mounted to the left of the windshield). I've checked the wiring for the front left components thinking it was crossed with a power wire or something, but me trying to reroute it had no effect...the whine was still there. any way the corssover could be causing this? I haven't looked at it yet, what would I look for?

Quote :

"also, at least on the sirius box, make sure you're grabbing its power from the same lead as the HU"

I'm pretty sure I am (same ground too), but I'll check.

Quote :

"so you're driving the crossovers on the components from the audiobahn amp as well as the 6.5s in the back?"

yep. not using the alpine internal amp at all.

Quote :

"if you hook up a spare speaker to one of the speaker terminals in the main harness, is the wine still there w/ accessories plugged in? i.e. is it only coming out of the preouts"

i spose i can try this (with the only one thats really making any noise)

Quote :

"you should go find a decent multimeter"

No worries there, I've got a fluke true-rms

3/11/2008 8:52:00 AM

so you only get the whine from the left front tweeter when an accessory is plugged in?

strange indeed... disregard everything i've said, i thought it was on everything coming out of the preouts.

try hooking the amp out straight to the mid (bypassing the crossover) and see if the whine shows up then... if not, then you know it's either the crossover or the tweeter (most likely the crossover). (actually, on second thought, this won't do shit... components don't have 2-way mids, duh)

try swapping the L/R amp outs to the crossovers and see if it shows up in the other pair of components

just work your way backwards until you don't hear the whine.

3/11/2008 8:56:40 AM

if you are only getting the whine from the front left tweeter, switch the left and right rca inputs on the amp running the front speakers. If it still comes out of the front left then it is a problem with the amp or speaker wire to that speaker. If it moves over to the right hand side then it is a problem with the RCA's or headunit.

If it stays with the front left, put your rca's back the way they are supposed to be and switch the left and right speaker OUTPUT on the amp. If it stays on the left, it is your speaker wires or crossover. If it moves to the right, then it is a bad chanel on the amp.

3/11/2008 12:02:15 PM

^that's pretty much what i just said.

3/11/2008 1:51:24 PM

what awg is your amp ground wire??

do the two amps share a common ground or are they separated??

stupid question: is your power wire from battery to amps separated from speaker wire and RCA's?? Imho, this shouldn't matter if you use quality-shielded cable, but its just something to rule out....

3/12/2008 5:38:39 PM

^^^^,^^^

thanks for the input guys, I'll take another whack at it soon

Quote :

"what awg is your amp ground wire??"

I think I have a 4 gauge coming into a distro block, then 8 gauge going to each amp (2 total), then 8 gauge ground wires coming off of each amp.

Quote :

"do the two amps share a common ground or are they separated??"

I'm not sure if they are grounded at the same place, but I assume so

Quote :

"stupid question: is your power wire from battery to amps separated from speaker wire and RCA's?? Imho, this shouldn't matter if you use quality-shielded cable, but its just something to rule out...."

I'm pretty sure the 4ga wire going to the amps is run on the opposite side of the car from the signal wires, but i'll check

3/18/2008 9:49:22 AM