I have just installed a JL Audio 500/1 Slash v2 along with a 13.5" W6, I grabed the signal from the preamp outs on the factory head unit, I used Twisted sheilded pair and hooked the wires up according to the only wiring diagram i could find, but i was for and 04, the colours werent the same, so i just chanced it with placement, seemed to work the sub sounds great and hits LOW just like i wanted, but for some reason now every time i have the amp on i get a high pitched hum only through the front speakers
(the lines i used for the signal to the amp) that changes pitch but not to anything like the engine or windows, then it will drop down in frequency and disipate to nothing, only to come back a minute later.

anyone have experience or know what this problem is... oh and yes i did not connect the sheild to the amp, i cut i back from the RCA plug, about half an inch.

 

I don’t know what you mean when you say you connected the shield to the amp. I assume that you connected the shield from the twisted pair cable to some point on the JL that you consider ground (hopefully it is not the RCA jack). First thing is, you don’t connect the shield on the twisted pair cable to the power amp. So disconnect it and see if the noise goes away.

Where did you connect the shield wire at the factory amp?

jeff

 

Does your car have NAVI by chance? I can hear the DVD player through the speakers. I was looking at tapping the harness and attemping to improve the ground on the unit.

 

I thank you for the info but in what i wrote above said, I did not connect the sheild to the amp or to the rca or anything on that end, its end is within the insulation of the wire about an inch from any connection on the amplifier end,,I know better than that.. and up front i connected the sheilds to the lines that serve as the sheilds(2 lines left and right) for the front speakers between the head unit and the amplifier...Now.. I'm positive at this point its the amplifier sending some sort of feedback along that line because the sound is not present when the amplifier is off, note that im still using the factory amp to power the mids and highs, this was not a amplifier bypass i just tapped into the preamp lines according to a wireing diagram i found for an 04tsx like i stated before, the colours never matched up but i just went by pin position in the wireing harness, i got the signal and it works, but does anyone think there was any changes in the amplifier used for the 04 compared to the 07?, maybee the shields were moved to a different pin position? i really have no clue, its the only thing that i can think of even though it doesnt make sense.

Oh, and the sound (humming) stays at a steady volume level it doesn't get louder when i turn the volume up...

And its not a navi sorry, its a non navi...

 

The pin out is the same so as long as you followed the pin #s you are good.
You can try two things; first see if the noise goes away when you unplug the RCAs from the new amp. Then try it with the RCAs plugged in and the new amp powered off. Just disconnect the amp turn on lead.

Let me no if the noise changes or goes away when you do this.

jeff

 

o.k. I tried what you asked and the noise was gone both ways...

 

Ok, then this won’t be easy to fix. If this was a Windows system you would get “the application has performed an illegal operation and must shut down” message. Basically you can’t connect your amps this way. I will have to do some research and possibly some testing to try to find the best way to do this.

If you can switch your sub amp to full range you should try to see if you get the hum out of the sub amp as well (use a full range speaker for the test). If you get the hum try unplugging the factory amp.

I’ll let you know if I come up with something easy.

jeff

 

Hey, I'am unable to switch my amplifier to fullrange because it does not have this function so i have no way of telling if the sound was effecting the sub as well, however i did my own trial and error today i tracked it down to be the signal wires, so i double checked to make sure that the shield was not touching or coming close to touching any connection on the amplifiers end, it was good the sound was still there, i started thinking it might be the wire it self, maybe it was a bad wire, after all the wire i used is off an old pair of xlr cables i had lying around. So i was ready to disconnect the wires and try new ones so i figured why not try one more thing, i cut the wires i was using for the shields from the front and tried the system one more time, The HUM is gone , now why is this not making any sense to me, the shield is to eliminate the interference not cause interference. I double checked the connections in the harness by number like you said before and everything was correct, any reason i have no noise now that i disconnected the shield, i know the humm is gone and i should be happy but its not making any sense to me and i would like to make sense of it...

 

Good troubleshooting!

The shield serves no purpose with a balanced audio feed except to supply a ground reference or ‘safety” when interconnecting mains powered equipment. By connecting one end to the shields on the factory harness and then leaving the other ends ‘floating” you can create an antenna of sorts. Since you have two different amps tied to the same output you have lost some of the noise rejection of the differential amps and it is possible that the extra noise the shield was picking up might (or did) sneak past the input stages of the factory amp. It’s fine to leave the shields off.

jeff

 

Hey jeff, if i cut the shields from your harness, would my hum and hiss go away too?

 

You need a modified harness. Shoot me a PM

jeff

 

Yeah, I was going to order it when I got back home to MD for the summer. ( I am in miami for school and I dont have the tools to take everything apart). But can this be a quick fix until I can order it?

 

No, it won’t work for you, The OP had a problem with a double termination and by cutting the shields he reduced the RF but did not get rid of it. Cutting the shields for the harness could make things worse. I can set you a set of Dongles that you can use until you can change your harness out. The dongles will suppress the interference but the harness puts the suppression at the HU end where it is needed and is less “heavy handed”.

jeff

 

What does the dongles consit of?