I had my 4 door speakers replaced with JL Audios and powered them with 2 separate amps (Pioneer and Kenwood) after bypassing the EQ. The installers were finally able to get rid of the alternator whine due to a bad ground but they can't get rid of the hiss when I have the volume turned down to almost nothing - it's rather annoying when the CD changer changes and all you hear is the loud hiss.. can anyone help solve this??

 

Will the hiss go away if you turn down the amps gains? If so, they may be set too high. As I have found the hard way, properly set gains should not hiss.

 

I have the gains set to minimum on both actually - I even had all new wiring put in throughout the car. Should I just chalk it off has one of the drawbacks of keeping the stock HU?

Perhaps since I have amps powering the 4 door speakers and the stock HU still powering the sub, could that be why there's still hiss?

 

Whoops, I assumed you changed the head unit. I cannot be much help with the stock unit as I changed my head unit. There are alot of people on here you kept it though.

 

Well I'd like to know from folks who kept the stock HU if they were able to eliminate HISS completely???

 

Same problem here. Are the gains on the input converter behind the radio turned down?

 

Yeah - the LOC gains were turned down as well - I mean the hiss isn't as blaring as it was when I had external tweets but in, that made it sound harsh and the hiss was awful. It's better - but as anal as I am about decent sound quality, I really don't like having any hiss at all.

I'm sure sometime down the line I'll give in and put in an Alpine HU but I really am trying to keep the stock look of the dash... (I even put in a wood dash trim kit)

 

Do you have a popping noise when you turn on/off the radio? Are the loc gains turned way down below 1/2 way?

 

I did have a popping noise but it was because of a bad ground - I've eliminated that along with the alternator whine. I don't believe the LOCs gains are lower than 1/2 though - will that affect hiss level?

 

Yes, that will cause some hiss as well. Try turning those down. I know it is a pain in the ass, but will help with eliminating the hiss. allthough it might not be perfect but that is the downfall of keeping the factory H/H.

 

I have no hiss w/ stock HU and external amps. I tapped the pre-EQ'd signal and ran it directly to my amps via an isoltion xfmr. The EQ is still connected and feeding the rear doors only.

From my experiences with this HU, you can get noise when,

1) Some amps will ground the signal before it is amplified. The stock HU signal is grounded also, thereby setting up a ground loop on your signal. Solution is to install a good isolation xfmr or LOC between HU and amps to break the ground loop. Or you could install a balanced line driver/system.
2) The HID ballasts put out a noise on the power system when the lights are on. I believe that noise could be coming thru on the remote wire. A simple power supply filter should remove most if not all of it.
3) Do not use those crimp-on taps/connectors to get your signal. You need to solder these joints. Crimp-ons should be outlawed. You put good money on RCA cables but then use 5 cent crimp-ons to pick a signal - just doesn't make sense.
4) If your RCA's are directional, recheck to make sure they both are pointing in the right direction per mfg.
Good luck

 

Are you saying to turn down the gains on the LOC? If anything you should turn the gains upto the MAX on the LOC's.

I too get a hiss when I turn the gain on the amp up. I tried two different LOC's and two different amps and the same thing happens.

I believe the problem is the radio which puts out a VERY VERY low power with the EQ bypassed. I'm guessing somewhere around 4-5 watts per channel RMS which causes the preamp level coming out of the LOC's to be knocked down alot. Maybe as low as .5V. Does anyone have an O-scope to measure the actual voltage coming out their LOC?