I've just added another amp to my system and now i'm getting a hissing sound though the speakers. My system is:

Headunit - JVC KDSX995
Front - Infinity 6500cs Splits
Rear - Infinity 9603i 6x9s
Amp - Infinity 7540a 4 channel
Sub - MTX Thunder 5512
Sub Amp - Jaycar Response Monoblock

Now with the wiring i'm running 4awg with an ANL fuse to an Aerpro Fused Distro Block. Im then running 6awg to both the amps and 6awg earth.

The rca and the power leads run down opposite sides of the car.

It is not engine nosie as its not running.

What could be causing this hissing sound?

I've just added another amp to my system and now i'm getting a hissing sound though the speakers. My system is:

Headunit - JVC KDSX995
Front - Infinity 6500cs Splits
Rear - Infinity 9603i 6x9s
Amp - Infinity 7540a 4 channel
Sub - MTX Thunder 5512
Sub Amp - Jaycar Response Monoblock

Now with the wiring i'm running 4awg with an ANL fuse to an Aerpro Fused Distro Block. Im then running 6awg to both the amps and 6awg earth.

The rca and the power leads run down opposite sides of the car.

It is not engine nosie as its not running.

What could be causing this hissing sound?

what did u change? did u just add the jaycar monoblock amp? what else did u change?

off the top of my head...upgrade both the 6gauge ground cables...where are the amps grounded?

mine used to have a hissing sound when the key was turned over twice.

1- off
2- only stereo turns on, speed alert comes on too
3- ACC i think it is (air con will works)

in position 3 i used to get a hissing noise.

I added the jaycar amp to run the sub. When i originally had installed the guy grounded it underneath the back seat with a screw. So i moved it to 2 seprate ground points on the behind the back rest on the rear seat using some exsiting bolts there, with the paint sanded back.

The hissing sound occurs in any off the key positions but stops when the volume is turned off. When i turn it to 1 it starts again. The 6awg power is only about 20-30cm long for the power and about 30-40cm for the ground.

After playing around with it, it is only coming out off the 6x9s. So when i unplug the rca lead for the 6x9s it stops, i plug it back up and it starts again.

Just sounds to me like you havn't grounded it properly.
Each amp should have a different ground point and make sure that you test the spot you are grounding it with a multimeter to make sure it's grounded 100%.

Is there any reason why it is only coming through the back speakers and not the front when its running off the same amp?

After playing around with it, it is only coming out off the 6x9s. So when i unplug the rca lead for the 6x9s it stops, i plug it back up and it starts again.
Either you havent ground it properly or and this is what happened to mine.

One or both of your RCA's have shorted the earth inside your headunit. (Both RCA's are earthed in the headunit)

I did this with my Pioneer. Took it in and they resoldered the earths.

is you're RCA running close to you're power cable?
I had the same problem, moved the power wire and loomed the power cable and problem solvered

yeh, take a look at ur cable positions.

its all just a process of elimination.

rip out the front RCAs and plug them into the rear RCA plugs, so it plays out of the 6x9s in the rear. if it is hissing, then it could probably be headunit, RCA, AMP or speaker. If it doesn't, then its from the headunit/rca cables.

go and get a 3.5mm to RCA cable, and play some tunes out of a CD walkman or somthing, plug it into ur amp. if that still hisses, then its ur amps/speakers

if it doesn't then its ur headunit and or rca cables.

The rca and the power leads run down opposite sides of the car.

Its not that and i thought that only occured when the engine was running


One or both of your RCA's have shorted the earth inside your headunit. (Both RCA's are earthed in the headunit)

2 of the RCA's are new. How would this have happened?

I have just redone the grounds to 2 seperate bolts on the metal part between the boot and the cabin. I check that there was no paint on there and it is clearly a better ground considering the original installer didnt even bother to clear the paint before he grounded it with a self tapping screw

Its not that and i thought that only occured when the engine was running



2 of the RCA's are new. How would this have happened?

I have just redone the grounds to 2 seperate bolts on the metal part between the boot and the cabin. I check that there was no paint on there and it is clearly a better ground considering the original installer didnt even bother to clear the paint before he grounded it with a self tapping screw

i think bain was talking about dry joints inside the headunit. it happens when the amp tries to ground itself through the rca cables and this blows the rca soldering because they're not made to handle such a high amperage.

trial and error- eliminate possible sources to find where its coming from ;)

go and get a 3.5mm to RCA cable, and play some tunes out of a CD walkman or somthing, plug it into ur amp. if that still hisses, then its ur amps/speakers

Ok i tried this and there was no hissing.


rip out the front RCAs and plug them into the rear RCA plugs, so it plays out of the 6x9s in the rear. if it is hissing, then it could probably be headunit, RCA, AMP or speaker. If it doesn't, then its from the headunit/rca cables.

Then i tried this.

Now i started at the amp. I turned the sub off. Its not the sub :) . Then i swaped the front and rear rca. It came through the front. So i think it could be the rear rca(the lead is less than a week old). pluged it back up and moved to the headunit.

Swap the front and rear rcas. Still coming through the rear? hmm... Pulled both rca leads out and this hissing was the worst its been with no connection from the head unit to the amps. Put it back to normal and still coming through the back.

I'm getting confused now :confused:

Check rear rca lead. Pull it out and re run it away from CPU, away from power lines etc.

Also make sure it doesnt run near the power lines as they enter the amp itself and make sure it doesnt run alongside the amp.

You have established that it is in the rear rca as the noise switches to the front when u change the cable.

So it is either the rear rca or the head units rear rca tracks.

Had a mate come around and found out it was the cable for my neon that was causing it. Don't know why it has started now cos i have had it running down the same side of the car for the last few months. Oh well its fixed now. Thanks for all the help.

a bit off topic but happened to my friend. some c**nt hit his car with a trolley and disturbed the driving light. when he turned them on it melted the insulation off the wire and it was glowing. thought sh*t and turned them off at the switch and the right one was still on (left one was hit by trolley and not working it grounded somehow). so we disconnnedted the FUSED relay (the fuse did not blow?? :nuts: ) and the right light was still on. htf did it still light up when it had no possitive but only ground? :nuts: had us so confused.

the moral of the story be careful if u see a trolly next to your car. if my mate started driving he would have been fu**ked. so much smoke hehehe