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Car amp BAD hum noise and whyyyy?


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I am trying to hook my car amp to my 12in sub for my theater and it won't stop humming. Sounds like a ground loop but there is no ground?? Using my denon avr as the sub out signal. Car amp (300 watt) is hooked to a 25 amp power supply and it hums... OK hooked straight off a big marine battery and yup it hums. BUT if i hook it up to my phone using a aux cord it sounds perfect on both the battery and the 25 amp power supply?? I tried a hum eliminator and that was a joke at best. Did nothing except kill the rca signal and hum. I have tried un hooking everything in the room. Computer, mini fridge, lights, tv and nothing helps. The room is on its own circuit and nothing else is on the breaker. No internet no cable etc.  I have tried 3 separate denon avr receivers and all the same. The rca is routed far from any other wires. Tried 4 different rca's and it never changes.

Tried 2 amplifiers and no change.

The amp is a rockford punch 300.1 on a crossfire c3 12. ported 

I tried my jl 1000/1 and same results (except it pulls more than my power supply can handle) but on battery is the same. I really don't want to do a powered sub because I already have all the stuff to do it this way and it it LOUD except the damn hum.

Any thoughts would be great.

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1 minute ago, bmwking said:

if you have it all hooked up and humming, what happens when you turn down the sub gain on the head unit?

hums  from the second i plug cra's into my denon it hums. sub volume all the way down or 0 db 

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is the plug that youve been plugging everything into properly grounded?  like if you take the plate off the wall and pull the socket out of it's box, does it have a black, white, and green wire going to it?  (assuming you're in the usa).  that's the only thing i can think of that's common in the hum, the outlet you've been using.  

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35 minutes ago, bmwking said:

is the plug that youve been plugging everything into properly grounded?  like if you take the plate off the wall and pull the socket out of it's box, does it have a black, white, and green wire going to it?  (assuming you're in the usa).  that's the only thing i can think of that's common in the hum, the outlet you've been using.  

yup

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34 minutes ago, BassMunky said:

Grounds?

there isnt any grounds involved. The receiver is only a 2 post plug. My pc that hooks into the receiver is grounded and correctly. I tried using a ground eliminator witch in theory should work but does nothing. I tried the same with my power supply.

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Theoretically a ground loop hum only happens when 2 pieces are hooked up and the grounds are slightly different. As I am only using 1 thing that's grounded (pc) it shouldn't have a problem. But just to check I plugged just my denon in and ran it to my car amp on a battery and it hums. There is no ground in the circuit to make a ground issue. That's why I'm so stumped.   And the whole room is on the same dedicated and properly grounded circuit so it really makes no sense. 

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3 hours ago, bmwking said:

if you have it all hooked up and humming, what happens when you turn down the sub gain on the head unit?

same. no change. volume does not change it either. with music paused or not even playing the hum is the exact same.

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