Sub Woofer Hum (another one) - AVS Forum
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post #1 of 6 Old 10-13-2011, 03:58 PM - Thread Starter
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I have HSU VTF3 MK3.
When the subwoofer is on there is a hum that is noticeable with the gain partially up (say around 8 oclock). If I turn the gain up the hum gets louder and is very noticeable at about 12 oclock and plainly audible throughout the room at max. So it is not a huge buzz but definitely annoying to someone actively listening, and concerning since I'd like the capability of turning up the gain for future use in a larger room.
Now the kicker here is that with only the subwoofer AC cord plugged in I have no hum at all gain levels, with any RCA cord plugged in I hear the hum, even when the amplifier end of the RCA is disconnected completely from my AVR. (i've tried RG6 with f-rca adapters, quad shielded RCA from monoprice, and random RCA cables around my house). RCA in Subwoofer with nothing else connected, hum. RCA out, No hum. IT is a constant hum, not hissy or static-like, and it does appear to be mitigated as I turn down/activate the Low Pass filter.
Also, the hum dissipates slightly when plugged into the avr. One other weird thing, when I touch the outside of the RCA plug (not the middle pin but the metal termination outside ring), the hum goes away completely. What is this hum, keeping in mind the HSU subwoofer has a cheater plug built into it.
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post #2 of 6 Old 11-15-2011, 08:17 PM
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did you ever found a solution? as I have the same problem with a new sub woofer I just got.
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post #3 of 6 Old 12-30-2012, 11:29 PM - Thread Starter
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Sorry its been ages since I've signed in. It never went away, I learned to live with it, since I was still getting plenty of output at only the 9 o'clock area. Figured it was the consequence of a lot of EMF in my room. Unfortunately, some other, minor imperfections have cropped up and wanted someone to hold my hand and reassure me about my perfectionism; noticing normal amplifier noises and thinking there are real issues. I'm a bit of a Hypochondriac regarding my home theater gear.
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post #4 of 6 Old 12-31-2012, 06:48 AM
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Quote:
Originally Posted by arigg View Post

when I touch the outside of the RCA plug (not the middle pin but the metal termination outside ring), the hum goes away completely.
That indicates the hum is EMI/RFI. When you touch the plug your body acts as a capacitor, shunting the hum. Every guitar/bass player is familiar with this, as it's endemic to their instruments. It shouldn't occur with a subwoofer when the interconnect is plugged into the AVR though, as the low output impedance of the AVR should shunt it as well.
Quote:
the HSU subwoofer has a cheater plug built into it.
That could be a contributor. Have you tried reversing the plug? If it's polarized you may not be able to without grinding down the larger pin.

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post #5 of 6 Old 12-31-2012, 09:36 AM
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I have twin Velodyne 10" subs in my HT that hum loudly when connected normally to my system. To make a long story short, my experimentation discovered that it was being caused by my TV/net cable from my TV/ISP system - this is very common.

I ended up attaching the 'outside barrel' of an unused RCA Jack on each sub to the 'outside barrel' of an unused RCA Jack on my TV - just zip wire with alligator clips. Hum completely gone.

Hope this helps...

TAM
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post #6 of 6 Old 01-02-2013, 05:16 PM - Thread Starter
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Thanks for the info. I'm fairly certain its EMI. Tried everything and received reassurance that even naked f type to RCA adapter can be fair game for EMI.
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