Alternator whine

bokdaddy

Hey guys, I installed a pair of mm651's in my rear doors a couple weeks ago and everything was working great. All of a sudden I'm getting some nasty alternator whine.

I re-grounded the amp in a different spot... still whining.

I pulled out the RCA's and ran them outside of the car to get them as far away from the power as possible.... still whining.

I unplugged the RCA's from the head unit.... still whining.

I tried grounding the preouts on the head unit in case it would work like it does for Pioneer head units (mine's a Kenwood).... still whining.

I plugged my ipod directly into the input on the amp for the rear speakers... still whining... from all four speakers... what the heck...

There is no whine when there is nothing plugged into the inputs on the amp, but there is a slight hiss. Nothing noticeable without putting your ear right up to the speakers.


What else can I try? And why did this come on suddenly? The amp has been in the car for a few months and there was no problem until a few days after the last time I added something to the system. (The mm651s)

decal

I had the same thing happen to me about a month ago. I regrounded the amp to fresh bare metal and it stopped. If your RCA cable is unshielded, try swapping it out for one that is. It's also possible that your amp and new speakers don't like one another. Don't laugh, it happens more than you'd think. In my home system, my ProJect turntable and the phono section in my amp don't jive at all, hum city. It works fine with my outboard phono-pre and other TT's thru the amps phono work fine. Go figure. Good luck and let's hope the amp isn't damaged.

bokdaddy

Thanks for the tips but regrounding didn't work and the cables are in fact shielded... plus, as I said when I plugged my ipod directly into the amp I was still getting the whine. So it couldn't be the RCAs or the head unit.

Vital

bokdaddy wrote: »

Thanks for the tips but regrounding didn't work and the cables are in fact shielded... plus, as I said when I plugged my ipod directly into the amp I was still getting the whine. So it couldn't be the RCAs or the head unit.

Try different amp.

bokdaddy

Vital wrote: »

Try different amp.

If the amp was bad wouldn't it still be whining when there was nothing plugged into the amps inputs?

exalted512

not if it was the inputs. I'm leaning towards bad amp., unless both your grounds suck.
-Codys

Drenis

Try a different amp. If the problem stops, that was your issue.

Joe08867

I am think the amp is having issues on the input side.

EBAN44

Have your tried moving your crossovers? There is a chance they are sitting on something putting off noise and picking it up. I'm in the same boat as you are, but have yet to move them since they are tucked under my dash and probably just going to run new wire to make them active if I'm going to take off the dash again.

bokdaddy

EBAN44 wrote: »

Have your tried moving your crossovers? There is a chance they are sitting on something putting off noise and picking it up. I'm in the same boat as you are, but have yet to move them since they are tucked under my dash and probably just going to run new wire to make them active if I'm going to take off the dash again.

Hadn't even considered that. I'll try it today. Hope that's it! This is driving me crazy. And I don't have another amp to test.

bokdaddy

Well... moved the crossovers this past weekend, no change. So I set out to get an amp from a friend. I ended up borrowing an Alpine PDX-4.100. Which by the way, as far as the wiring process goes has got to be the most annoying amp I have ever seen. But I digress...

I hooked up my friend's amp and the good news is my amp isn't the problem.

The bad news is my amp... isn't the problem.

The Alpine was putting out the same noise that my RF Punch P400-4 was putting out.

Now a little more info:

I have two amps hooked up in my car. A RF Punch P300-1, and a RF Punch P400-4. I switched my speaker wire over to the P300-1 and checked my rear speakers. No whine. Switched back to the P400-4. Whine again. I have tried different grounding points in the car which made no difference. I am using distribution blocks for both the power and the ground. 4 gauge in, 8 gauge out to the amps. Doesn't seem like it's the power wiring gauge or they should both be whining. And to be sure I did ground the P400-4 on it's own to no avail. The RCAs for the front are run on the left side of the car with the power and the RCAs for the rear are run on the right side alone (And the whine didn't begin until after I installed the rear speakers, so it couldn't be noise from the power cables reaching the front's RCAs). All four speakers are putting out the whine. And as I said, I pulled out the RCAs and ran them far from the power on the outside of the car and still no change. And also, once again, I plugged my iPod directly into the amp and still had the whine.

Now I'm whining haha.

What's next guys? I'm completely at a loss here.



Thanks,

James

decal

Take it to a professional.

bokdaddy

decal wrote: »

Take it to a professional.

Not to sound rude, but if I had the money to pay someone an undetermined amount of cash just to diagnose it I already would have. I'm asking for help because I've spent all this money on four mm series speakers and an amp and just can't afford more expenses at this time. So if anyone has any other suggestions I'd greatly appreciate it.

Vital

Re-run those RCAs away from power cables. Even if you had no issues with it before it still could be the cause as with time things move/shift a bit. That bit of a shift could be exactly what you are looking for now...well, trying to get rid of lol.

One time I was losing my mind over an alt noise out of a blue after months of my install was after I played around with my sub. A week of bugging out and constant trying to figure i "why" I did - because my subs speaker wire was moved by closer to power wire by literally 2 inches. THAT was the cause of my whine. I move speaker wire 2'' to the right - no noise, 2'' to the left (towards the power wire) - NOISE.

KaosTsoc

+1 ^ on his suggestion. Also what kind of Hu are you using? Stock or aftermarket? In some cases, if the HU voltage is too low, it can allow that hissing noise to bleed through. In other words the HU might not put out enough voltage to keep that hissing noise come coming through. Not always the case, but this was one of my issues. I had an aftermarket HU though, and its pre out were only like 2v max, normally it would be like .5V, or 1V, which was not enough power. It was allowing for that hiss to come through. The hissing got worse the faster I drove the vehicle, and would then kind of go away when I slowed down, but the noise was always present. Even if I had the HU on, but had the volume turned all the way down. When I turned of the radio, the noise went away do to no power.

I was able to fix this issue, by doing two things. 1. was what vital said above. Make sure my power, and speaker wires were not close to each other. If they do have to cross each other you want to cross at 90 degree angles instead of side by side. 2. was to get a HU that put at least 4V or more. This higher voltage allowed for my music to come through with better clarity, and had enough power to push out, and eliminate that hiss noise.

This may or may not be your issue, but since I have been reading this, and following it I figured I would put this out there, cause it sounds similar to what I was dealing with at one point. Hope it helps...

Thanks.

bokdaddy

Vital -

Thanks for your input it was actually your mention of your sub speaker wire that led to the fix. It was pretty random but without your quick mention I don't know if I would have figured it out. I had actually ignored the possibility of the speaker wire being the culprit for some reason. When I did the install I swapped in a wire I had been using for the surrounds in my home system and just assumed it was a good wire. I had completely forgotten about the problem I had 7 years ago when I was still in college and my speaker wires were chewed by the pet bunny one of my friends had. I ran the RCAs on the opposite side of the power wires and started disconnecting the speaker wires one by one to get them as far from the power wires as possible as well. When I disconnected the wire that was connected to the front left speaker it stopped. So I took the wire completely out and sure enough the wire was exposed in few spots. So I swapped in some fresh wire and bang - all fixed.

Kaos -

Thanks for the tip on the HU voltage. I'm using a Kenwood BT-845U and there is a slight hiss still but nothing that can be heard unless the car is off and you're really listening. It might be something I look into fixing down the road.

Thanks again guys. I can't express how valuable this forum has been to me on a number of occasions. I've been self-teaching myself about home theater and car audio for nine years now and wouldn't be able to get past my sticking points without this forum. Even when no one is able to come up with the exact answer I needed your advice always seems to lead me to a fix somehow.

With great appreciation as always,

James

Drenis

Sometimes its the littlest things.

codyc1ark

Very nice, congrats.

Vital

Glad you got it resolved!!

adurm

The hiss might be a little over gain on the amp. Try backing down the input gain if you can tolerate the decrease in volume.