i've spent the last week or so trying to get rid of a hiss/white noise/static that plays at all times (acc position, engine on, head unit off, ipod on pause, xm music). i can hear it even at volume set at 0 and at louder volumes it just gets masked. i don't have that completely crisp and clear sound i was looking for. it doesn't change with rpms and there is no whine.

amp is jl xd500/3 that i bought used and was supposedly in great working condition

it's especially annoying when there are pauses in music or the vocals are nearly quiet because there is the hiss/static/white noise.

it's not the head unit or the rca inputs because the noise is still there (although quieter) even with no inputs connected.

the hiss does go away with lower gains but there is still a hum in my sub from the static even at the lowest amp gain on that channel (running sub signal post oem amp). i'm trying to get full power out of my components while minimizing the hiss.

i've also tried using a line driver and a ground loop isolator with no success. i've tried two different grounding points, both with paint scraped off.

should i try hooking up another amp to see if it goes away? i'm considering ordering a new xd500/3, check to see if it works and then return it if not, but wanted to see what other ideas there might be since that's a hassle. should i leave my gains low and just accept the lower hiss?

 

anyone have any tips?

 

Trying a different amp would be a great way

 

i have a new amp arriving on monday with a full return policy in case it behaves the same.

i also contacted JL and they gave me a test method to try out tonight to see if it is in fact the amp. they told me to short 4 RCA plugs and put them all into the inputs and then run a remote wire from the power slot to the remote wire.

this will close the loop and tell me if the noise is coming from the amp or not

 

If the hiss goes away with lower input sensitivity then I think you have your culprit. The JL manual has a procedure for setting the input sensitivity levels.

If you are getting hum on the subwoofer, have you disabled the Adaptive Noise Canceling circuitry?

I would disconnect the sub and go through the input sensitivity setting procedures. What input impedance are your speakers? Lower impedance speakers will be more sensitive and need lower input sensitivity on your amp. Once you have the L&R outputs to your liking then work on the sub. Check the ANC. If the ANC is disabled check the input wiring to the amp.

Good Luck

 

 

Thanks for the response back, i came across a lot of your posts during my research and appreciate your knowledge.

input sensitivity: my cd player is broken so i can't run a disc with a constant sine wave, so i can't hook up my multimeter and read the voltages. i tried hooking up my ipod with a sine wave but the voltage reading was strongly influenced by the ipod volume and it wasn't set correctly once i went back to FM/XM. my ipod volume was on max, and when i went to a different source the bass was non existent. if my cd player worked, i would do the gains per the instructions and know it's right.

instead, i had to take it to a local audio place and they just tuned it by ear. i currently have the gain lower than what they set it at to reduce the hiss some but it's still there and i'm at about 40% gain.

ANC: i disabled the rear mic before installation. when i started having hiss issues, i took out the main control unit under the center channel and it had no effect on the hiss, so i put the unit back.

impedance: my FL/FR speakers and tweeters are 2 ohms. they are grabbing signal pre-stock amp. the sub is wired to 2 ohms and the signal takes post-stock amp and the gain is turned all the way to the minimum.

per JL customer service, tonight i ran 4 shorted inputs into the amp and grabbed the remote turn on directly from the battery, and the noise just about disappeared, considerable decrease.

i emailed them back my results tonight but am not sure where to go from here. the test told me it's most likely not the amp, so i'm back to square 1 haha.

could the location of my passive crossovers under my passenger seat (electronics under there for seat movement and seat heaters) have some effect on the static/hiss/white noise?

 

So with the shorting plug in place the hiss is reduced. The shorting plug is just grounding the input and in effect isolating the amp and speakers. How are you interfacing your iPod? Through the aux input or directly into the amp? What happens when you play music from your iPod? Just adjust the iPod volume with music to have a level about what you use with the radio. Keep that iPod volume level and set the input sensitivity.

If that still doesn't work, describe how you are running the audio signals into the amp. Are these the HU pre-amp inputs or are you using the stock amp speaker level outputs? Another good test would be to play your iPod directly into the amp inputs, use a 1/8" to RCA adaptor cable. If this is clean then the focus would be on the amp input cable.

 

I see you added some info.

Try setting up the system first just using the front L/R inputs. Take out the sub input and set the XD500 input to the two channel mode and set the LP and HP to 80 hz. This will simplify the setup.

The crossovers are using the high level amp outputs, their location shouldn't matter. Hiss is almost always related to amp input sensitivity settings.

 

thanks for the feedback!

FL/FR: HU pre-amp
sub: i installed connections for both pre amp and post amp, but currently running them post amp

the ipod is hooked up through an isimple. i even tried removing the isimple cable in the trunk and no effect on the hiss. there is more hiss with the ipod but i just realized it's still at the max volume setting and the guy set my amp using the xm songs (so it has higher gain when using the ipod).

good idea, i'll try messing with the ipod volume to match the xm level and try to set it with the DMM. i'll look for that adapter you mentioned.

i've tried running the setup in 2 channel mode and my crossovers are already set at 80 hz. the noise is still there.


i'll mess with the ipod this weekend and try to get it to match up with the HU

 

so i have more info now and wanted to see if there are any thoughts or suggestions on what to do. i recently got a new (used) oem head unit with a working CD so i was able to set the gains for my sub using a DMM and a proper test tone through my CD players

however i can't set my front components (2 channels) to the correct gain for a 4 ohm load because of the hiss.

the hiss is still there even when not reaching the pre determined voltages. i can take the RCA inputs out of the amp and the hiss is still there. i've tried a brand new amp and the hiss is still there.

could this be a ground issue? right now my ground wire under my driver's seat is 24" and i was thinking of cutting it down to 12"?

i currently use all stainless steel hardware to bolt the ring terminal to sanded, bare metal under the drivers seat. anything else i could do?

the sound overall is great (got new image dynamics components) but there is a noticeable hiss when there is a pause or quiet part in the music

 

Buddy your ground is fine, I would double check the grounds under the hood, if anything ground your block to the a better grounding points of your car, and reground your battery, its a small 8G wire that holds everything from battery to ground point. I have used 0G for mine.

damn dude, i know you been working on this for a while, did you take it to shop like you said you would? I don't have a problem with mine and running 3 massive amps in my car, but again, i'm not using stock radio...

 

I do not have the hiss, but I have upgraded the overall grounding of the car. see my thread.

https://acurazine.com/forums/photogr...nstall-606115/