I have a 2003 SR5 with non-JBL radio

I am running a factory head unit to factory speakers with a 35 RMS per channel amp. I am using speaker level input. I had tried using a LOC, but that resulted in alternator whine.

I have the gains at min and there is a small hiss. IF I turn them up it gets worse.

With the car off, accessories on, radio off I hear the hiss and it seems to pulsate. In the same scenario, if I turn the radio on it gets louder and I can not hear the pulsating.

With music playing, I can hear a slight hiss if I pay close attention. When the music stops, I can hear the hiss tail off.

I tried muting plugs with the amp and with those in and the gains maxed out, the hiss was minimal (I could live with it).

Any tips on how to proceed?

 

sounds like is what you described it as, alternator interferance

they make several cheap products to get rid of that. go to your local stereo shop and tell them, or go to www.crutchfield.com they ahve some good stuff, but are kinda overpriced

here's a link

http://www.crutchfield.com/cgi-bin/S...=0&cc=01&avf=N

 

Sounds like a ground problem to me. Have you tried hooking up everything to an extra ground wire that runs all the way up to the batt minus?
And maybe a ground loop filter just before the amp can be a good idea. I've had similar problems and was able to solve them with a 10 buck filter from a car audio store.
I know that this 'hiss" can drive someone crazy.
Good luck!

 

The hiss does not vary with speed. Does that rule out alt. interference?

 

If it happens with the engine not running, you can rule out the alternator.
But it can be another electric interference. Maybe something is switched on or a remote door lock module or whatever. These things sometimes interfere with each other. And that is why it is sometimes very hard to find.
If have had this once with my Hilux diesel and no electrics (everything worked 'maually'). Only a battery, a stereo with amp and thats it. But still nobody was able to solve the f..g problem.
I even hooked up an HP oscilloscope and tested every situation and wire. Still zippo. So I sold it and got me a 4R.

 

Does the fact that with muting plugs in the noise was minimal elimnate the ground and power connections to the amp, or is this a bad assumption?

 

It probably dampened it so it will not be as noticable. But that is also an indication for a ground loop or signal loop. Provide a good mass to all the stuff, use at least the same diameter as your supply wire. If you only use the body or chassis as a ground, than that is likely the source of your problem.