subwoofer makes all speakers hum - AVS Forum | Home Theater Discussions And Reviews
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post #1 of 7 Old 04-21-2019, 10:47 PM - Thread Starter
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subwoofer makes all speakers hum

I just got a denon x4400h because my sony za1000es is not meant for the 4 ohm speakers that I have.
Now, whenever I plug my subwoofer into the denon, (to either subwoofer 1 or 2), it makes all the speakers hum. This does not happen when
I duplicate the setup with the Sony.
The receiver I got was a refurbished one, and when I first got it, the menu wouldn't come
up, and the screen looked like the picture below. Then it just randomly started working, after power cycling it 4 or 5 times.
Is it possible this is from a faulty receiver?
And more importantly, could that humming cause damage to my speakers?
it's not that loud, but wondering if whatever is causing the interference could cause internal issues in the speaker components.
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post #2 of 7 Old 04-21-2019, 11:16 PM
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Quote:
Originally Posted by Steve Brueshaber View Post
I just got a denon x4400h because my sony za1000es is not meant for the 4 ohm speakers that I have.
Now, whenever I plug my subwoofer into the denon, (to either subwoofer 1 or 2), it makes all the speakers hum. This does not happen when
I duplicate the setup with the Sony.
The receiver I got was a refurbished one, and when I first got it, the menu wouldn't come
up, and the screen looked like the picture below. Then it just randomly started working, after power cycling it 4 or 5 times.
Is it possible this is from a faulty receiver?
And more importantly, could that humming cause damage to my speakers?
it's not that loud, but wondering if whatever is causing the interference could cause internal issues in the speaker components.
No humming won't damage the speakers. No it's probably not caused by defective receiver.

Most likely you have a ground loop since both the sub and the receiver plug into the wall in separate outlets. Try lifting the ground leg on the subwoofer power if it has a 3 prong plug. Most subs should utilize a 2 power plug to prevent this sort of ground loop. Usually the receiver is the only component with 3 prong cord. At least this is a good place to start. Another option may also be to run a small wire from the ground on the receive chassis to the ground on the plate amp on the powered sub.

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post #3 of 7 Old 04-22-2019, 07:59 AM
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Quote:
Originally Posted by Steve Brueshaber View Post
…The receiver I got was a refurbished one, and when I first got it, the menu wouldn't come up, and the screen looked like the picture below. Then it just randomly started working, after power cycling it 4 or 5 times.

Is it possible this is from a faulty receiver?
Does that sound TO YOU like the refurb was working to factory specs?

Trick question. It doesn’t, to me.
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Last edited by ChromeJob; 04-22-2019 at 09:06 AM.
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post #4 of 7 Old 04-22-2019, 10:43 AM
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Don't leave the sub cord ungrounded!

Yes, it's Ok to lift the ground on the power cord to test and see if this is causing a ground loop but don't use that as the fix. It's setting up a dangerous future shock hazard.

Blue Jeans Cable now sells a $50 transformer isolator for sub woofers. This is a great solution for most home systems. The other sure way is to run balanced lines but that is expensive and the facilities are not found on most consumer gear.

Some people just use sub woofer cables with heavy grounds, like video grade coax cable. This partially works because there is less resistance on the ground wire and therefor less ground loop current can flow. But IMO, this is only a partial fix. The best bet is to use an audio isolation transformer.
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post #5 of 7 Old 04-22-2019, 06:06 PM
 
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As I understand it, although I'm not dead sure, it would be safe to use a cheater plug to bypass the third prong (ground) if there is a GFCI upstream to protect you.
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post #6 of 7 Old 04-22-2019, 11:40 PM - Thread Starter
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thank you everyone for the great advice. I will do these tests tomorrow and see you about getting that isolator if need be. I do have a GFCI so I hope to be good with that if i get rid of the 3rd prong.
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post #7 of 7 Old 04-23-2019, 07:05 AM
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I've seen too many GFCI's fail over the years to trust my life to one, even though technically I do anyway whenever I am in the woodshop... I would not use a cheater plug as a long-term solution.

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