Need HELP with alt whine

[zigzagflux]

That would certainly work, as would transformer coupling, nice for breaking ground loops.

If one is interested in using amplifiers in their car (and you have two of them), there is no excuse for NOT having a head unit with true preouts.

If the head unit doesn't have them, junk it and buy a $100 head unit that does. It will sound better in the long run.

[pityocamptes]

Ok. Thanks. I got rid of the lines and am only using the preamp out put. It still makes the noise no matter if I have the HU on or the EQ on. Both units make the noise regardless. Any other thoughts? Thanks.

[I Am An Idiot]

Originally posted by Perry Babin
Measure the resistance from the shield ground of the head unit's RCA jacks to the case of the head unit. The resistance should be near zero ohms. Do this with no RCAs plugged into the jacks.

I read that you checked the EQ, but have you checked the RCA jacks of the radio? Remember as Perry stated earlier unplug the cables from the radio before checking this.

[zigzagflux]

Exactly.

Fundamentally, it comes down to isolating where the noise is entering the system. You start out with only the amplifiers connected. If no noise, add in the EQ. Then add in the HU. At some point, you will get the noise.

Then it comes down to how that noise is entering. It could be insufficient grounding of each component; could be a broken shield in the cables; could be a defective component, etc.

Edit: if you can run the amplifiers alone with no input, and have a quiet signal to your speakers, you confirm it is not the alternator's fault, it can be filtered out by a decent power supply design.

[pityocamptes]

Edit: if you can run the amplifiers alone with no input, and have a quiet signal to your speakers, you confirm it is not the alternator's fault, it can be filtered out by a decent power supply design.

I unplugged the inputs and I do not get a noise at the speakers from the amp. Not sure where to go from here. Thanks.

[zigzagflux]

Okay, now plug the EQ RCA into the amp and listen. Do not connect the head unit. Note any noise.

Then, plug the head unit RCA into the EQ and listen. EQ is still plugged into the amp, of course. Note any noise.

[I Am An Idiot]

Originally posted by Perry Babin
Measure the resistance from the shield ground of the head unit's RCA jacks to the case of the head unit. The resistance should be near zero ohms. Do this with no RCAs plugged into the jacks.

Should I change my screenname to I am Invisible?

[ppia600]

Originally posted by I Am An Idiot



Should I change my screenname to I am Invisible?

Haha, almost the same thing happened to me in another thread.

http://www.diyaudio.com/forums/showt...hreadid=107715

Hey pityocamptes, is your location oregano,onion,tomato or cilantro,cebolla,tomate?

[1moreamp]

Engine noise is made under the hood, not by the stereo. there are super grounding kits for your engine compartment that solve the problem at its roots under the hood.

If that fails Jensen still sells the best audio transformers out of the LA basin, about $140.00 a stereo set, but flat response and studio grade product.

The Grounding kit for your engine is a lot cheaper. It consists of a huge corrosion proof negative battery terminal, several feet of 2 gauge or larger grounding cable, and 3 or 4 gold plated lugs that you use to terminate the connection ends with.

Seems that if you run several 2 gauge conductors, one from the Alternator body, one from the engine block, and one from the distributor securing bolt, and one final cable to the firewall. All come back and terminate on the super negative terminal on the battery that this kills engine noise at its source, and may solve your issues without the transformer wiring headache your going through inside your cab of your truck.

Your stereo is a victim of the noise your truck is generating under the hood. I would tend to fix under the hood before pulling your hair out on the stereo. MHO, I hope you find this useful...

[ppia600]

If he's worried about sufficient ground source from the alternator to the car's body/frame/chassis, the only thing needed is a thicker ground strap(s) from the engine block to the car's body/frame/chassis. I'd really like to see you measure the resistance difference between a relatively small piece of copper strap to the resistance of the super thick engine block. So you're saying the piece of wire has less resistance? There may be a voltage difference between the block and the firewall, but there is none (that you can measure) between the alternator chassis and the end of the block where the stock strap is bolted.

I don't have the "engine grounding kit" you speak of but I do have two thick grounding cables going from the engine block to the car's body and the battery. They aren't to take care of the magical voltage fluctuations some people claim occur on the engine block. I just installed them to get the current from the block to the car's body easier. More current for the starter and for my amps. I never had engine noise issues before installing the wires either way, even with the flimsy stock ground strap.