INSTANT alternator whine after replacing one amp!

Jammin06Ion

I know, there are probably a hundred posts somewhere in the forum about whine, but after reading a few, I figured I'd just post my own personal experience since others seem to be related to specific reasons for alternator whine from different sources.

I have pages and pages of notes on alternator whine, what causes it, how to pinpoint its source, and how to eliminate it. But since mine only came on suddenly, I figured I'd run it by the forum and get some opinions.

Okay, so I had absolutely NO whine at all UNTIL I removed my powered sub and installed my brand new Polk Audio PA-D1000.1 mono amp and Alpine Type-S 10" sub. Now all of a sudden I have major whine below about 2,000 RPM. The strange thing is that it's coming through the tweeters and front full-range door speakers, not the sub (because the sub won't reproduce those highs).

My alternator is a new 150-amp, and since I installed it, my voltage has always ran at 13.8 to 14.1 when the engine is running or I'm driving. I've never got it below 13.5 volts even with headlights on and stereo blasting and even the heater on. Everything is grounded properly with the same 4g cable sizes at the amps as the power cables.

Like I said, I never had this whine until yesterday when I pulled out my powered sub and installed this new Polk Audio amp in its place. I used the same power, ground, turn-on and RCA cables (very high quality twisted shielded cables from KnuKonceptz) because they were already there, ready to hook up. I barely needed to move any wires at all.

I can't think of what would have caused this whine instantly. My RCA cables (one 4-channel to the Eclipse 4-channel amp and one 2-channel to the Polk Audio mono amp) are run on one side of my console and routed under my back seat, then up behind the seat backs to the amps. My turn-on lead comes from a relay I mounted inside the dash, and that wire is run under my console on the other side. My battery is in the trunk (it's a Saturn Ion) so my amp power cables are short, and there is no chance of them crossing the RCA's.

I'm just stumped here. I've dealt with alternator whine before, but never had it just suddenly start after replacing one amp. The only "good" thing about this is I don't hear it when I turn up the volume a little, only if the volume is down or it's between songs.

I would HATE to find out it was something wrong with the brand new Polk Audio amp! But I have to start somewhere.

SeleniumFalcon

I'm not sure what caused the sudden increase in alternator whine, but usually a capacitor is installed on the alternator's 12 volt terminal connected to ground.

Jammin06Ion

I'll try that. Not sure if there was already one there or if this is something I need to put in myself. If I have to do it, I need to figure out what size.

SeleniumFalcon

Another good idea is to run the amplifier's ground connection all the way to the battery's negative terminal (I know that could involve a lengthy connection if the amplifier is in the trunk) using a fairly high gauge wire. Using the car's chassis as a grounding point creates a less than ideal ground.

gmcman

How is the new amp secured compared to the last amp? I assume on the same mounting surface, but what about a mounting screw that could be into the chassis creating 2 grounding points.

I don't know how yours is mounted, but maybe that could cause an issue?

Jammin06Ion

SeleniumFalcon wrote: »

Another good idea is to run the amplifier's ground connection all the way to the battery's negative terminal (I know that could involve a lengthy connection if the amplifier is in the trunk) using a fairly high gauge wire. Using the car's chassis as a grounding point creates a less than ideal ground.

My battery is in the trunk in the spare tire well, so it's only maybe 4 feet away if that.

Jammin06Ion

gmcman wrote: »

How is the new amp secured compared to the last amp? I assume on the same mounting surface, but what about a mounting screw that could be into the chassis creating 2 grounding points.

I don't know how yours is mounted, but maybe that could cause an issue?

In the exact same place, on the back of the rear fold-down seat. But YES, that could have happened. I didn't put it exactly in the same holes since this amp is so much smaller, but on the same rear seat. For spacers, I used plastic spacer rings from a tv wall mount because they don't show up like the small wooden blocks I used before.

Jammin06Ion

Good point though! I never thought of that! If one of my screws hit a piece of metal inside the seat, I guess it could generate through the hinge and create an issue. But the ground wire from the amp is going to a ground under the spare tire cover in the trunk about 2 feet away.

pitdogg2

It is possible to have two different ground potentials. That in itself will cause a humm. All grounds need to end at the same place and ground plane.

gp4jesus

You definitely have ground potential SOMEWHERE?

Which side did you run amp’s RCAs?

Can you turn on the system leaving the sub amp off but otherwise connected. Try that w/the sub amp’s RCAs
1. connected
2. if still noisy, disconnect one RCA; try again
3. if still noisy, disconnect the other RCA; try again
4. if still noisy, connect the first RCA, disconnect the other RCA; try again
5. Now w/ both RCAs unplugged powering up the sub.

Back in the 80s, w/very few exceptions, power down the drivers side, signal down the passenger usually resulted in a noise free system. I recently viewed a Steve Meade (SMD) YT video where he grounded the car’s (Honda) alternator w/cable about 2-3 times the thickness of the vehicle’s battery ground as a preventative measure - noise free system.

Hope this helps.