Aftermarket head unit + stock amp amp/speakers = hum?

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LTrain0800

LTrain0800

10 Year
Joined
Apr 18, 2011
Threads
18
Messages
294
After reading some of the stereo threads on here it seems normal that an aftermarket head unit ran through the factory amp/speakers will produce a low level hum in the system. Mine has this hum when I turn on the stereo but the hum doesn't get any louder when I turn up the volume. It's just annoying when there is no sound or the volume is turned down.

Is there a way to eliminate this noise completely?

Joel
 
LTrain0800 said:
After reading some of the stereo threads on here it seems normal that an aftermarket head unit ran through the factory amp/speakers will produce a low level hum in the system. Mine has this hum when I turn on the stereo but the hum doesn't get any louder when I turn up the volume. It's just annoying when there is no sound or the volume is turned down.

Is there a way to eliminate this noise completely?

Joel
Click to expand...

A few more details would be helpful.

Year? Model? Stereo Type Model? How did you hook the aftermarket headunit to the factory amp?
 
Check your RCA cables and possibly put a filter on it. I had the same issue and eventually had to yank the factory amp and replace it with an aftermarket clean amp.
 
ground loop isolator and/or an RF filter on the 12v into head unit

x 2 the ground loop isolator. plug it in right before the RCA inputs on the amp.

$14.99 at Crutchfield, probably cheaper elsewhere, but crutchfield has great service.
PAC SNI-1 RCA Ground Loop Noise Isolator at Crutchfield.com

If that does not fix your hum, you can also run an RF filter inline on the 12v power input to the headunit.

American International S-15A (15-amp/250-watt) Power line noise filter at Crutchfield.com

Sometimes aftermarket head units pickup RF hum off of the alternator.

Does the pitch of the hum change depending on the engine speed?
If no, then use the ground loop isolator.
If yes, then use the RF filter on the 12v power into the head unit.

Cheers.
 
CRUIZIN said:
Is there a quick way to explain how to do this?
Click to expand...
Yes and no. As you've read above, and in other threads, there is no universal root cause and hence, fix for it. I hooked up my stereo and then depressingly noticed the buzz. I unbolted it from the dash, and hooked it all back up with the HU sitting on the gear shifter. I then unhooked one by one, each component (with the entire car off, of course) until the hiss went away. GL isolator went on that circuit. In my case it was an auxiliary video line that was causing the problem. This was with a Kenwood DNX6140. Others with different HU's have had different issues, some seem to be as yet unresolved. Best of luck. BTW, I'm running the factory amp, and OEM speakers (I know, I know...)
 
marshotel said:
x 2 the ground loop isolator. plug it in right before the RCA inputs on the amp.

$14.99 at Crutchfield, probably cheaper elsewhere, but crutchfield has great service.
PAC SNI-1 RCA Ground Loop Noise Isolator at Crutchfield.com

If that does not fix your hum, you can also run an RF filter inline on the 12v power input to the headunit.

American International S-15A (15-amp/250-watt) Power line noise filter at Crutchfield.com

Sometimes aftermarket head units pickup RF hum off of the alternator.

Does the pitch of the hum change depending on the engine speed?
If no, then use the ground loop isolator.
If yes, then use the RF filter on the 12v power into the head unit.

Cheers.
Click to expand...

THIS.
 
I just remembered that the factory amp on the 100 series has proprietary inputs, not RCA plugs.

To avoid mangling the wiring under the seat, you could plug the ground loop isolator into the RCA outs from the headunit (assuming it has them); as long as you put this in the signal path between the head unit and the amp, it should work.
 
Thanks for the breakdown Marshotel, I will have to try the RF Filter since the noise varies with engine RPMs.
 
Thanks for all of the useful information on eliminating my stereo hum everyone. My noise doesn't change and is there when the engine is off. By the way I have a Kenwood DDX6019 in my '99. It's funny, the noise is there using XM, regular radio and video but is gone when using the cd player. I need to pull it out and start eliminating sources one at a time to try to figure out the culprit.
 
Ha, there was a guy on here no more than two weeks ago that had nearly and identical issue with his JVC. The only difference was his would quit humming in AUX mode. He ended up just bypassing the amp all together.
 
I have this same noise on my 2000. It increases with the motor rpms. Do I need 2 of the power line noise filters? Since there is 4 rca jacks that come out of the stereo. I am lost when it comes to car audio.
 
I had a Kenwood head unit driving the factory amp/speakers and had the same hum. I tried eliminating the ground loops, but that was nearly impossible since the factory head unit was powered by the factory amp. I ended up just bypassing the amp and driving the factory speakers directory from the Kenwood head unit. That of course meant no subwoofer. Sound was better than factory, but still not great. But at least I bluetooth and hum was gone!

Eventually, I put in an aftermarket amp (JL Audio XD700-5v2) and new head unit Pioneer 4100NEX and Polk Audio speakers. Sounds awesome now even with the factory subs.

2000 LC

Sent from my GT-N5110
 
RootMeanSqr said:
I had a Kenwood head unit driving the factory amp/speakers and had the same hum. I tried eliminating the ground loops, but that was nearly impossible since the factory head unit was powered by the factory amp. I ended up just bypassing the amp and driving the factory speakers directory from the Kenwood head unit. That of course meant no subwoofer. Sound was better than factory, but still not great. But at least I bluetooth and hum was gone!

Eventually, I put in an aftermarket amp (JL Audio XD700-5v2) and new head unit Pioneer 4100NEX and Polk Audio speakers. Sounds awesome now even with the factory subs.

2000 LC

Sent from my GT-N5110
Click to expand...
Did you have trim the main tombstone to get the 4100nex to cycle its faceplate motor? I am having a hell of a time. I'm guessing trimming is in order
 
I have a video player and it's the same way, it picks up noise from the alternator
 
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