amp or sub?

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Forum Name: Car Audio
Forum Discription: Car Stereos, Amplifiers, Crossovers, Processors, Speakers, Subwoofers, etc.
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=114486
Printed Date: May 13, 2025 at 3:32 PM

Topic: amp or sub?

Posted By: mantis_rr
Subject: amp or sub?
Date Posted: June 16, 2009 at 12:05 AM

I just installed a second mrd-m1005 mono amp. Their is a humming noise that I guess is coming from the amp and when I turn the gain up the noise gets louder through the sub with no music. The first amp/sub is fine with no noise, just the second amp/sub. It happens when I have it just in ACC or if I start it. I don't know if it's the first amp out's or the second amp in's. Any ideas?

Replies:

Posted By: i am an idiot
Date Posted: June 16, 2009 at 12:41 AM

Run signal to the new amp first. Then from that amp to the old amp. If the problem is the output of the old amp, this situation would be fine. If there is noise in both amps after switching them around, the new amp is probably the culprit.

with an ohm meter, remove all RCA cables from both amps, how many ohms are there between the shield of the RCA jacks on each amp. Black lead on an input shield, red lead on an output shield? Check both amps.

Posted By: mantis_rr
Date Posted: June 16, 2009 at 12:58 AM

Switched them up and now it's on the other side, so that means it's the second amp that I installed then?

Posted By: mantis_rr
Date Posted: June 16, 2009 at 1:01 AM

I dont have a meter with me but I'll check it tomorrow when I have one

Posted By: i am an idiot
Date Posted: June 16, 2009 at 5:42 AM

Your easiest out will be to purchase a set of Y adapters, 1 male 2 female, and use them instead of the output jacks. There may be nothing wrong with either amp, you may have a ground loop that can be cured with the Y adapters.

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