I installed a speaker level converter with my system, and a major noise is coming out from the head unit. I have bypassed the whole system, no amps, speakers, everything. I thought I had noise coming from the cables, grounding issue, but then I noticed I took the rca cables straight from the converter to a amp, and sub outside the vehicle, and the noise (Humming) was still happening when the vehicle was running. I also noticed that when the doors are opened, with the engine running, no noise. With the motor not running, no noise. I also tried to put a rca filter on the converter, but no luck. I have to basically turn the gain down on the converter to about 1/8 of its power to avoid the noise, but then the levels are too soft. Its amplifying the noise. What's up??? Thanks

Sounds like feedback from your speakers.

and ran the rca to the amp outside the vehicle.

Does your LOC have a ground wire?

my guess is ANC (Active Noise Cancelling). the head unit uses a mic to "listen" for low frequency engine sounds/vibrations caused by the VCM (cylinder deactivation) when the engine is in 3 cyl mode. it then takes what it "hears", flips the sound 180 degrees and plays it through the speakers to cancel it out. since you amplified it or whatever, the "flipped" sound being played back through the speakers is amplified too, causing it to overcompensate instead of exactly canceling out the sounds, thereby creating the noise again.

can fix that noise canceling with a kit, I will check it out.

any luck with that?? i'm going through the same problem and can't find a solution.. were you able to find a kit? or did u end up installing the OEM stuff back in??

I disconnected the noise canceling unit, by unplugging the little harness. And I have not noticed one thing yet.....

did it actually make any difference in hearing the outside noise or the dash noise and etc.?

the car is quiet, just like it was installed....

and one last question.. where was the harness you unplugged?.. is it in the passenger door?....

or is it in the back of the head unit..?

Any updates on where the plug is? I'm having similar issues with my '08 accord with humming noises when the engine is on and the radio is off. When the car is off but the aux power is running the radio, I hear nothing so I don't think it's an amp or an installation issue. Any help would be greatly appreciated.