Chasing an amplifier whine

[fastpakr]

I installed a 5 channel amp a couple of weeks ago in the Ranger and have had a background whine since then. My intent was to leave troubleshooting it for later because there are other things higher on the list to deal with. However, I ran into a curious symptom yesterday: at KOEO (engine off but ignition in the run position), the pitch of the whine is in direct correlation to throttle position. As I open the throttle, the pitch increases steadily to about 50% throttle, then remains steady above that.

Any thoughts on what would cause the TPS to feed back that way? This issue was not present (or at least not noticeable) without the amp. It definitely exists on two similar JVC radios I've tried. The amplifier has a 4 gauge ground to a bare metal connection about two feet away where it's bolted down where one of the jump seat bolts would normally be. Power is run by 4 gauge wire through a grommet on the firewall and connects to the factory distribution box on the drivers side. The radio is grounded using the factory ground wire in the dash radio harness.

 

[Ranger850]

I had a Punch 40 on 2 "12's that whined, after making sure the grounds were all good, I notices on of the RCA jacks had a minute amount of wiggle. if I played with it I could get it to stop. Had the amp tested - bad ground INSIDE the amp. I was supposed to send it to the manufacturer for a repair but the cost of that was more than I payed for the amp, so I just ran my subs off ome channel and got a new on for the Hi's & mid's. Eventually got rid of the Punch for an Alpine V12.

So I would check the amps channels. 5 channel amp? what brand and How many RMS watts? ( just curious )

 

[Curious Hound]

Happening with engine off? Weird. First thing I would do is run the amplifier ground directly from o the frame. Also, make sure speaker grounds go back to the equipment. Don’t use the body as a ground path for speakers.

 

[fastpakr]

Happening with engine off? Weird. First thing I would do is run the amplifier ground directly from o the frame. Also, make sure speaker grounds go back to the equipment. Don’t use the body as a ground path for speakers.

Yep, engine off. Do you just cut a hole in the floorboard and run it out through a grommet to the frame? I don't mind doing that, just hadn't anticipated that being necessary.

The main speakers are still on the factory wiring. I ran four speaker cables from the amp to the dash behind the radio, and put in an 8 pin connector on the radio harness so I could swap between the radio and amp as their signal source.

 

[fastpakr]

I had a Punch 40 on 2 "12's that whined, after making sure the grounds were all good, I notices on of the RCA jacks had a minute amount of wiggle. if I played with it I could get it to stop. Had the amp tested - bad ground INSIDE the amp. I was supposed to send it to the manufacturer for a repair but the cost of that was more than I payed for the amp, so I just ran my subs off ome channel and got a new on for the Hi's & mid's. Eventually got rid of the Punch for an Alpine V12.

So I would check the amps channels. 5 channel amp? what brand and How many RMS watts? ( just curious )

It's a cheapo - Soundstream PN5.640d. I think they rate it at 60x4 and 200x1 @ 4 ohms. It's feeding a set of 6.5" components up front and 6x9's in the back (I cut the factory holes out to fit those in, and using adapter plates up front for the 6.5's. Sub is a 12" RF 2 ohm SVC in an enclosure I grabbed from Crutchfield.

https://www.crutchfield.com/p_530PN5640D/Soundstream-Picasso-Nano-PN5-640D.html?tp=259
You can grab the amp on Amazon for about $140. It's tiny - small enough to easily fit under a seat. I've had one in my wife's Acura for about three years.

 

[91stranger]

I would get rid of the amp. Cheap products = cheap sound. How do you have the power wire sourced at? If you are getting power from a distribution box then that is where you might be getting interference. You can also get interference from the 12v outlets like for a car charger if you have a charger or something that you leave plugged in. I have a 1000 watt Memphis amp and a 12" kicker L7 and I don't get any weird noises unless I have a charger plugged in. I have my power coming from the actual battery post and the ground is just attached to one of the front seat bolts near the floor. Been like that for a few years now. DONT BUY CHEAP when it comes to sound. Don't be that guy trying to push 4 12's with a 500w walmart amp.

 

[fastpakr]

Cheap amplifier or not, that doesn't explain the TPS noise being in the mix.

I'll try running the power directly to the battery to see if that has an effect.

 

[Ranger850]

My amp wasn't an El Cheep-O, "Punch" by Rockford Fosgate is/was pretty reputable when I had it, just got worn out over time. I would still check the amp's rca jacks for interference. Or like @91stranger said, it could be feedback from a junction box. I would run power from the battery with a good fuse @ the battery, I only use "Monster" brand wires when I can, not the cheap wiring kits from WallyWorld. But then again I haven't installed any stereo equipment in a while. Everything my be different than it was 10 yrs ago. Monster cables may be available @ WallMark(?) I have a box of goodies waiting to be installed after I figure out what the hell I'm doing with the 4 bucket seats I have.

 

[91stranger]

Or you can just buy a noise filter for less than $20 and be done with it. Crutchfield has a good page about how to find/fix noise. here is the link https://www.crutchfield.com/S-P1dKB...car/noise_suppressors_installation_guide.html