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03 with Rockford Fosgate system head unit replacement - weird sounds

10K views 14 replies 5 participants last post by  Delirious 
#1 ·
So I just wired up and plugged in my new JVC KW-HDR720 head unit (http://www.crutchfield.com/S-1h5FMA1jusd/p_105KWHD720/JVC-KW-HDR720.html) in my '03 with the Rockford Fosgate sound system, and I've noticed that I now have a repeating low-tone thumping noise that comes through the speakers when the vehicle is turned off. It seems to go away when the ignition is set to on. I noticed that it goes away when I unplug the speaker jacks from the back of the head unit, but I'm not sure if it's originating with some. The fact that it only happens with the ignition turned to off makes me wonder if maybe it is the security system interfering (it's a stock security system so no idea on the specs/wiring). It does, after all, have a flashing light, so it may be sending out some weird signal whenever it goes off.

Anyone else heard this?
 
#3 ·
Yep, it routes through the factory amp using the adapters provided by Crutchfield.

I decided to just pull it out and pop it back in, as I realized I had forgotten to disconnect the battery last time. So, I did that, this time correctly disconnecting the battery, and the background popping while the ignition was off went away, but it was now popping whenever the radio engaged or disengaged the sound. For instance, if I turned the volume all the way down, it would pop when I un-muted it, or when I switched equalizer settings. I called Crutchfield, and they said it was a known problem with head units that have RCA jacks in the rear being installed in Nissan vehicles with the Rockford Fosgate system, and that installing a ground loop isolater would fix the problem. They were kind enough to ship me out a new one free of charge!
 
#4 ·
Let me know if that works for you. I tried everything I could to stop the noise(s). The only thing that stopped it was running new wires to all my speakers and doing away with the factory amp all together. From what I understand there isn't a internal amp in the RF head unit, it just sends the signal like a rca line to the amp behind the HU. Once you hook up a new HU that has an internal amp, you are sending a amplified signal through an amplifier, then off to your speakers. I'm hoping someone will chime in and say if this is bad or not for any part of the system. I didn't like it so that's why I spent half a day re-doing it all from the HU back.
 
#5 ·
I know, stupid question but you always start with the basics... you did hook the blue/white wire in the harness to the blue/white wire on the head unit, correct? That's the signal wire to turn the amp on and off.

As for disconnecting the battery.. that's more to prevent a short than anything (I've done thousands without ever disconnecting it)

It *may* be a ground loop, but the way you said its thumping, to me, it makes it sound like a bad cap or circuit in either the jvc or the factory amp.

Sent from my GT-I9000 using AutoGuide App
 
#6 ·
I know, stupid question but you always start with the basics... you did hook the blue/white wire in the harness to the blue/white wire on the head unit, correct? That's the signal wire to turn the amp on and off.

As for disconnecting the battery.. that's more to prevent a short than anything (I've done thousands without ever disconnecting it)

It *may* be a ground loop, but the way you said its thumping, to me, it makes it sound like a bad cap or circuit in either the jvc or the factory amp.

Sent from my GT-I9000 using AutoGuide App
Yeah, I was pretty careful about matching everything up right after I noticed that two of the colors didn't actually match up. I went off the diagrams and descriptions to make certain everything was going to the right spot.

I'm anxious to see if this does actually work. As I said, the thumping is gone, it's just a pop when the amp receives a signal now.
 
#7 ·
If its popping when the system first turns on, and also maybe when it turns off (but not in between) then its most likely a timing issue. You can get turn on delay modules online for under $20, and what they do is delay the amp turning on a bit so the audio signal is already on. The pop usually happens when the amp is already on and *then* the audio feed kicks on

Sent from my GT-I9000 using AutoGuide App
 
#8 ·
If its popping when the system first turns on, and also maybe when it turns off (but not in between) then its most likely a timing issue. You can get turn on delay modules online for under $20, and what they do is delay the amp turning on a bit so the audio signal is already on. The pop usually happens when the amp is already on and *then* the audio feed kicks on

Sent from my GT-I9000 using AutoGuide App
Cool, I'll keep that in mind if this doesn't work. It does happen when it's powered on and sometimes when it's powered off, but it also does it if I change the radio station (the brief time between signals when it is muted to avoid static between stations), when I change equalizer presets, that sort of thing, not just when the head unit is turned on and of. Hopefully this ground loop isolator will fix it, but if not, it could be worth checking a delay module.
 
#9 ·
So the ground loop isolaters Crutchfield shipped out to me did the trick! Sound is perfectly clear without any extraneous noises when the ignition is shut off or when the amp turns on or off. It's a bit cramped behind the big double-DIN head unit with them in there, but hey, it works!
 
#12 ·
I also have the Rockford system and tried installing a new DVD head unit today. I'm also having terrible hissing and interference noises coming through my speakers. In addition, I am hearing this fan like sound coming from under my X, have no idea what's going on? I connected and matched everything correctly on the harness to the deck. How do you connect this Ground Loop Isolator thing? I uninstalled everything and put back the factory deck cuz the noise was so bad.
 
#13 ·
If its popping when the system first turns on, and also maybe when it turns off (but not in between) then its most likely a timing issue. You can get turn on delay modules online for under $20, and what they do is delay the amp turning on a bit so the audio signal is already on. The pop usually happens when the amp is already on and *then* the audio feed kicks on

Sent from my GT-I9000 using AutoGuide App
1kohm resitor on the amp turn on wire USUALLY fixes "turn on pop" on factory amps
 
#15 ·
also finds most nissans dont ground through the harness and gets their grounds in the ISO mounting brackets. most installed head units are only being grounded through the antenna (specially when using a plastic dash mounting kit)...not a good ground. run the HU`s ground dirrectly to a metal brace inside the dash cavity and usually all those popping, pulsing, altinator wine, etc noises will go away.
 
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