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JohnW

Subwoofer hum

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Now here’s interesting issue I can’t figure out.

 

I bought a never-used, still in the box, original Hsu Research VTF-2 Mk 1. I’d used one for fifteen years and loved it. Picked this one up for $100. It even still smelled new.

 

Anyway, plugged it in, everything was kosher. 
 

Until today. Turned on my receiver, which activated the sub, and there was a hum coming from it. Turned the receiver off, sub remained on, And kept humming.

 

Unplugged the rca cable (connecting the sub to the receiver), hum stopped. Tried a different rca cable, still had a hum.
 

Tried a different three-prong power cable, still had a hum.

 

Hmmm...

 

Tried a ground lifter. 

 

Hum gone. 
 

I’ve heard using a ground lifter Is a bad idea...but the previous sub used a two prong power cable....

 

Loose ground cable in the sub amp? 
 

Welcome to the boundaries of my knowledge.

 

Theories? Ideas?
 

 

 

 

 

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Hi john, per your request I deleted the double post.

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1 hour ago, dwilawyer said:

Hi john, per your request I deleted the double post.

Thank you much.

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2 hours ago, wuzzzer said:

This has everything you'll need:

 

 

Yes, but...one day without hum. I changed nothing in the system.

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15 minutes ago, JohnW said:

Yes, but...one day without hum. I changed nothing in the system.

 

But what else have you added/changed to the house as a whole?

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The ISO-MAX will solve your problem whether it is a ground loop or common impedance coupling. Problem is it will cost twice as much as the sub.

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5 hours ago, Thaddeus Smith said:

 

But what else have you added/changed to the house as a whole?

Literally nothing. 

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So you don't have a problem? This is double plus good.

You had a bad ground(shield) connection, you shook or wiggled something, broke through the dirt/corrosion or whatever and now all is good.

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37 minutes ago, babadono said:

So you don't have a problem? This is double plus good.

You had a bad ground(shield) connection, you shook or wiggled something, broke through the dirt/corrosion or whatever and now all is good.

No, I attached a ground lifter to the AC plug. Not entirely crazy about that. 

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So you DO still have the ground lifted. I thought you meant you got rid of the ground lift, but you meant the ground lift got rid of the hum. So do you want to fix the problem or keep the ground lifted?

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I’m trying to identify the possible cause of the hum, given that one day there was none, and the following day, there was. What commonly produces that sort of problem, Short of a change in devices in my house, of which there are none. 
 

Everything is plugged into a Belkin Pure AV PF-60 power conditioner. And that’s the real head scratcher.

Edited by JohnW

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Did you read any of the theory a few posts back? Especially starting on page 101. This will explain how to scientifically figure out what the problem is and how to remedy.

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Yea life, I get it. I should have pointed to page 101 when I first posted.

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