 Re: Subwoofer and receiver both humming
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Joined: Sep 2020
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OP
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Could be a leaky filter capacitor in the power supply. You could be more sure of that by cutting open a spare RCA cable, shorting the wires together and connecting the mess to the sub jack. That eliminates any possibility of airborne noise getting in via the sub's RCA jack. It is a high impedance input after all. Can you please elaborate/simplify on this? Are you suggesting cutting an end off of the cable, then joining the two wires inside together, then plug this shorted device into the rca jack on the sub?
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Re: Subwoofer and receiver both humming
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Joined: Sep 2020
Posts: 29
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OP
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Are you using a shielded sub cable? Yes it's a double shielded Monoprice cable
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Re: Subwoofer and receiver both humming
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Joined: Jan 2007
Posts: 10,490 Likes: 116
shareholder in the making
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shareholder in the making
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Could be a leaky filter capacitor in the power supply. You could be more sure of that by cutting open a spare RCA cable, shorting the wires together and connecting the mess to the sub jack. That eliminates any possibility of airborne noise getting in via the sub's RCA jack. It is a high impedance input after all. Can you please elaborate/simplify on this? Are you suggesting cutting an end off of the cable, then joining the two wires inside together, then plug this shorted device into the rca jack on the sub? Correct.
House of the Rising Sone
Out in the mid or far field
Dedicated mid-woofers are over-rated
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Re: Subwoofer and receiver both humming
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Joined: Sep 2020
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OP
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What exactly would this test prove?
wouldn't shorting it be a bad idea?
Sorry, I know you know far more about this stuff than I do, but this just doesn't make a whole lot of sense to me
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Re: Subwoofer and receiver both humming
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Joined: Sep 2009
Posts: 1,897 Likes: 101
connoisseur
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connoisseur
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Mojo, you or I would have built specialized connectors to track down these kinds of problems but best to keep it simple ... use a wire ...
Last edited by rrlev; 03/06/21 04:46 AM.
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Re: Subwoofer and receiver both humming
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Joined: Jan 2007
Posts: 10,490 Likes: 116
shareholder in the making
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shareholder in the making
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Shorting it as I described would be like your receiver putting out zero volts. No harm will be done.
Since the sub is humming without the cable connected, you may have airborne noise entering through the RCA jack. If you short the input and the hum disappears, that means you've shorted the airborne noise. If it still hums, it's likely a leaky power supply capacitor.
BTW, noise figures for audio equipment are always given with RCA jacks shorted as I described. The manufacturer wants to measure internally generated noise and not what might be generated by the ambient environment and radiated or conducted into the equipment by inputs and outputs.
Last edited by Mojo; 03/06/21 05:02 AM.
House of the Rising Sone
Out in the mid or far field
Dedicated mid-woofers are over-rated
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Re: Subwoofer and receiver both humming
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Joined: Jan 2007
Posts: 10,490 Likes: 116
shareholder in the making
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shareholder in the making
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Mojo, you or I would have built specialized connectors to track down these kinds of problems but best to keep it simple ... use a wire ... You can use a wire but then it's like a small antenna. Best to put some mu metal around the shorted RCA jack I say.  P.S. Jumbo might have to hold the wire and then it's like an antenna connected to a capacitor. There's no telling what worm hole Jumbo may open up.
Last edited by Mojo; 03/06/21 05:21 AM.
House of the Rising Sone
Out in the mid or far field
Dedicated mid-woofers are over-rated
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Re: Subwoofer and receiver both humming
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Joined: Sep 2009
Posts: 1,897 Likes: 101
connoisseur
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connoisseur
Joined: Sep 2009
Posts: 1,897 Likes: 101 |
Don’t think that’s would be a problem ... but it’s your show 
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Re: Subwoofer and receiver both humming
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Joined: Sep 2020
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OP
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I just tried it, it didn't make a difference, it's still humming.
It's barely audible but if I put my hand on the driver I can definitely feel it's doing something. I believe the humming coming from it when I first noticed it was louder just like my receiver than it is now. It's possible it's been like this for a while now, it's rarely quiet enough in my house to hear it with little kids running around all day.
So this sounds like a capacitor issue?
If I turn the sub off and then back on again, it doesn't hum at all and it doesn't start humming until the sub receives a signal to do it's thing. Once it's received that signal it wont stop humming until the power to it is shut off.
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Re: Subwoofer and receiver both humming
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Joined: Jan 2007
Posts: 10,490 Likes: 116
shareholder in the making
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shareholder in the making
Joined: Jan 2007
Posts: 10,490 Likes: 116 |
Is the humming affected by the sub's volume control?
Are you sure the hum returns only when signal is fed? Have you tried waiting a minute or so?
House of the Rising Sone
Out in the mid or far field
Dedicated mid-woofers are over-rated
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