Alternator Whine?

[Blackout67]

Have an amp that I've used in three separate vehichles now so I know it isnt the amp or atleast Im 99 percent sure. First was my truck, then my girls Camry, then my Jeep, then back in the truck. Both times I've used this amp in the truck it has a very loud and noticeable high pitched whining coming thru the subwoofer but not the door speakers. I can see and feel the cone moving. It gets higher pitched and louder when I rev the engine (doesnt do it at all when just the accessories are on even tho the amp is indicating that it has power) and dies down with revs so Im pretty sure its either picking up engine noise or alternator noise. The sound does is not affected by the volume of the HU or the the gain level, unlesss the gain is turned all the way off, then it stops. Didnt do this in my Jeep or the Camry.

Ground is to the body and very secure and its reading a steady 14.5 V even while playing music so im sure its not a voltage or ground issue, like I thought it was the first time I had the amp as it usually said around 13.6 when I first had it in there and the ground was not very tight and I was too lazy to fix it.

Looking for suggestions, dont want to run a ground all the way back to the battery if I dont have to, thats the most common solution I see and it doesnt always work anyway. and I've heard that there are ground loop isolators that will (maybe) fix the issue but I really dont think that it is anything to do with the ground.
My power wire is not touching my RCAs and I dont think that 4 gauge CCA will carry enough current to leak thru the thick *** insulation on the wire anyways.
Amp is a JP8 monoblock, truck is a 05 GMC Sierra with I believe the 130 amp alternator that came with the 4.3s

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[Doxquzme Premium Member]

Wire insulation does nothing on wire unless it is of the shielding type. You mention that it does not come through the door speakers which I assume you mentioned to indicate that the other amp(?) that powers the doors is not picking the noise up from the HU or other parts, right?

Assuming this is not replicated when the car is on AC so you are picking alt noise and that usually comes through the HU (ruled out)the transport of the signal (RCA's or LOC) to the amp or from the amp to the speakers as in the subs wiring (unlikely)..

 

[Blackout67]

Wire insulation does nothing on wire unless it is of the shielding type. You mention that it does not come through the door speakers which I assume you mentioned to indicate that the other amp(?) that powers the doors is not picking the noise up from the HU or other parts, right?

Assuming this is not replicated when the car is on AC so you are picking alt noise and that usually comes through the HU (ruled out)the transport of the signal (RCA's or LOC) to the amp or from the amp to the speakers as in the subs wiring (unlikely)..

Sorry should've mentioned, I don't use a DSP or LOC. RCAs straight from the aftermarket HU to the amp. Door speakers are still on HU power, happens when the AC is on and off

 

[audiobaun 5,000+ posts]

What radio do you have? Make and model#? Did you place RCAS on the Sub amp and or radio while in operation?

 

[audiobaun 5,000+ posts]

You can ground then rear battery by running a ground wire same size as power wire and bolt it to the axle to save wire and have a pretty much bullet proof grounding location, cleaned and using good terminals.

 

[Blackout67]

What radio do you have? Make and model#? Did you place RCAS on the Sub amp and or radio while in operation?

Pioneer DMH100BT and no, the battery was disconnected both times I installed the amp in the truck. Wouldnt I have to to drill into the floor of the truck to do that? Anyways it's a single cab long bed so the amp is actually closer to the front battery (I don't have a rear one) than it would be to the rear axle.

You think it could be a ground issue? Like I said the ground location was sanded down and cleaned and the ground wire lug is very snug and flat to the surface from what I can see. It's also reading a solid 14.4 volts, if the ground was bad it'd wouldn't be getting full voltage. That's the issue I'm having in my Jeep with my JP13 I just put in there

 

[Kickstand Premium Member]

How tight is your HU packed in there
Any chance the RCA's are pushed against anything or bent in anyway?

 

[Blackout67]

How tight is your HU packed in there
Any chance the RCA's are pushed against anything or bent in anyway?

I don't believe so. I'll have to take a look when I get home. I've had that HU pulled a couple times.

I just remembered tho there is a wire that is supposed to be wired to the parking brake (it's stupid the only thing that happens when it isn't connected is once all the slots are full in the Bluetooth pairing menu, you have to ground out that wire to be able to delete and add a new phone.

Then again this did not happen at all with the SFB600 I just had taken out the other day in the same truck

 

[maylar 10+ year member]

You shouldn't be hearing alternator whine through a sub. Is your LP filter turned on?