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Old 06-26-2016, 11:52 PM
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Constant static/hissing from aftermarket head unit

Hello. New to the forum. I've searched for an answer to this and can't find anything that is exactly the same. Any help is much appreciated.

I have an 09 JKU that originally had the alpine system. I switched out the dash and roll bar speakers and switched the factory head unit with an after market single din Sony. I am using a crux wiring harness to allow for the use of the factory amp. Everything was fine, except that the head unit would randomly reset itself every few days. So I returned it and decided I would rather have a double din HU. Chose the JVC kw-v120bt. I installed it and now I have a sort of loud hissing/static sound going through the speakers whenever the unit is on, whether it's playing anything or not. The sound doesn't change with volume, so I can drown it out by turning up the volume. But it's still overly annoying. I've checked all the connections I could think of.

Anybody had this problem or may know a solution? I don't know much about the wiring stuff, especially when the amp is involved. Just think it's weird that it didn't happen with the Sony but it does it with the JVC.

Thanks in advance for your help.

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Old 06-30-2016, 02:49 PM   #2
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Originally Posted by Jcramsey View Post
Hello. New to the forum. I've searched for an answer to this and can't find anything that is exactly the same. Any help is much appreciated.

I have an 09 JKU that originally had the alpine system. I switched out the dash and roll bar speakers and switched the factory head unit with an after market single din Sony. I am using a crux wiring harness to allow for the use of the factory amp. Everything was fine, except that the head unit would randomly reset itself every few days. So I returned it and decided I would rather have a double din HU. Chose the JVC kw-v120bt. I installed it and now I have a sort of loud hissing/static sound going through the speakers whenever the unit is on, whether it's playing anything or not. The sound doesn't change with volume, so I can drown it out by turning up the volume. But it's still overly annoying. I've checked all the connections I could think of.

Anybody had this problem or may know a solution? I don't know much about the wiring stuff, especially when the amp is involved. Just think it's weird that it didn't happen with the Sony but it does it with the JVC.

Thanks in advance for your help.
I'm not familiar with the JK wiring setups, but if you have any RCA connections, make sure the connections are clean and tight going to the HU or amp.

Second, does the hissing happen in any input mode on the HU?

Third, Did you use a pigtail harness to connect your HU to the factory HU wiring harness or did you splice into the main factory HU wiring harness?

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Old 06-30-2016, 04:07 PM   #3
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Ground wire to the radio chassis? Ground in the harness is for power, may or may not be connected to the radio chassis.
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Old 10-11-2016, 11:47 PM   #4
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I have the same EXACT issue. I just installed a JVC Double Din unit KW-V220BT and I have a constant hissing sound no matter the input. I triple checked all the connections and the ground is connected to the radio chassis, I pulled the grounds off and held them to the metal bar behind the dash and the noise is still there. Did you ever find a solution?

Any help is greatly appreciated.

Thanks
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Old 10-23-2016, 10:31 PM   #5
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Sounds like the gain hasn't been set up correctly on the amplifier.

The crude way to set up the gain is to turn it all the way down on the amplifier, put in some loud music, and crank the head-end's volume control to 75%. Now turn up the amplifier's gain until it's really loud but not distorted. I have found that 95% of people can't hear distortion that makes me want to rip my eyes from their sockets.

The real way to set up is using a pink noise CD, a 1/3 band equalizer, and calibrated lab microphone and matching spectrum analyzer software. Set the system to flat/close to it using the equalizer first. The head end's tone controls are used to adjust the music for taste.

Now use a CD running pure tones sweeping the spectrum from 20 Hz to 20 KHz while watching/measuring for distortion on spectrum analyzer connected to the line level outputs of the head end. Some units will hit full gain without breaking into distortion and others won't.

Knowing that distortion/non-distortion point connect the head end to the amplifier and again raise the gain while watching for distortion using a calibrated lab microphone.

Be aware that tweaking equalizer/tone controls can send the system into distortion quickly.

If the gain of the amplifier is jacked up very high the amplifier's will find and amplify the random noise found in the circuit. Lower it allows the head end to be that sound source.
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Old 03-05-2017, 04:31 PM   #6
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Could be that the JVC head unit needs a firmware update... I just installed a Kenwood DDX793 and noticed a "hiss" even with volume at zero. Turns out there was a firmware update available for my unit that seems to specifically address this. Pretty much gone now.

Same might apply to yours since JVC and Kenwood are one...
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Old 12-19-2017, 04:31 PM   #7
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Did You ever find a solution? Im having the same problem!
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Old 12-24-2017, 10:00 AM   #8
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Most of the time this hiss is due to a bad ground or ground loop issue. First thing to do is make sure you have good grounds at both the H/U and amp. Ideally these would be the same ground point but that is not always possible. If everything is ok there it is probably an issue with your RCA's.

How you would test for this is to make a jumper for testing. Attach one end of the wire to the H/U chassis ground and strip the other end to use as a prob. Now touch the prob end to the outside of each RCA. If the hiss goes away you found your bad ground. You can either spend money to have it properly fix or solder a small jumper wire to the RCA (outside) and ground the H/U chassis.

FYI: I have never had more than one bad RCA ground but I suppose it could happen.
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Old 01-03-2018, 09:01 PM   #9
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Do you know the location of the ground wires?

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Most of the time this hiss is due to a bad ground or ground loop issue. First thing to do is make sure you have good grounds at both the H/U and amp. Ideally these would be the same ground point but that is not always possible. If everything is ok there it is probably an issue with your RCA's.

How you would test for this is to make a jumper for testing. Attach one end of the wire to the H/U chassis ground and strip the other end to use as a prob. Now touch the prob end to the outside of each RCA. If the hiss goes away you found your bad ground. You can either spend money to have it properly fix or solder a small jumper wire to the RCA (outside) and ground the H/U chassis.

FYI: I have never had more than one bad RCA ground but I suppose it could happen.

Do you know the location of the ground wires?
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Old 01-04-2018, 07:02 AM   #10
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Do you know the location of the ground wires?
Well not exactly because every installation is different. On the H/U it will be the black wire coming out of the unit, normally spliced or solder to the factory ground wire. Unless there is a bad splice or solder joint this is normally not an issue.

The amp ground normally will be located somewhere near the amp. Hopefully who ever installed it prepped the ground well, removing an paint between the ground lug and chassis. You don't want to just count on the the nut or bolt providing the ground path.

The next thing to check is the RCA's. Take a look at this video on how to do this:

https://www.youtube.com/watch?v=6at6sRnkMRg

This normally happens because we screw up, we work hot and during our connection process grounding the center conductor and blew the fuse. You can take the radio apart or send it in to have it fixed but the simple fix is to ground the RCA to chassis. It doesn't need to be a big wire as shown there.

If everything checks out and the noise is still present we still have 2 more things to check for and that is RF noise, one caused by the engine and the other caused by the electrical system.

Engine noise, if the interference goes up and down as the engine is rev'd this is normally engine RF induced through the power leads to the H/U. What you would do here is hook up a ferret core filter on the power lead to the H/U. FYI I have not seen this be an issue on a modern car for a long time.

The last thing to check is electrical system RF noise. This normally happens when you route your RCA's and amp power cables together. Always best practice to run them either side of the vehicle. But all is not lost if you RCA cables came with a 3rd connection called a drain. The idea behind the drain is to is to shunt the noise to ground and in most cases it works great. On the H/U end of the RCA hook that wire up to ground and leave the amp end un-hooked. Some people like to use these wires and the amp remote turn on but unless the RCA specifically says it can be used for that purpose don't.


Remember that less is more here. Work thru each one at a time to find the problem. In the end if none of this proves to be the problem you have a bad H/U or amp.
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Old 01-05-2018, 04:00 AM
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Did You ever find a solution? Im having the same problem!
Are you using the Crux wiring harness? If so, I ended up contacting them and they had me add some resistors to the wires between the stereo and amp. They walked me through it and told me what size resistors to get. I would contact their customer service.
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Old 01-07-2018, 02:08 AM   #12
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see the noise mine makes is alot different than that, its like a quiet buzz. just a static noise.
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Old 01-07-2018, 06:38 AM   #13
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see the noise mine makes is alot different than that, its like a quiet buzz. just a static noise.
Nose is noise, volume don't really make a difference, trouble shooting is the same.
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Old 02-22-2019, 08:33 AM   #14
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Anyone find a fix?

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