JohnW Posted September 16, 2020 Share Posted September 16, 2020 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? Quote Link to comment Share on other sites More sharing options...
Moderators Travis In Austin Posted September 16, 2020 Moderators Share Posted September 16, 2020 Hi john, per your request I deleted the double post. Quote Link to comment Share on other sites More sharing options...
wuzzzer Posted September 16, 2020 Share Posted September 16, 2020 This has everything you'll need: Quote Link to comment Share on other sites More sharing options...
JohnW Posted September 16, 2020 Author Share Posted September 16, 2020 1 hour ago, dwilawyer said: Hi john, per your request I deleted the double post. Thank you much. Quote Link to comment Share on other sites More sharing options...
JohnW Posted September 16, 2020 Author Share Posted September 16, 2020 2 hours ago, wuzzzer said: This has everything you'll need: Yes, but...one day without hum. I changed nothing in the system. Quote Link to comment Share on other sites More sharing options...
Thaddeus Smith Posted September 16, 2020 Share Posted September 16, 2020 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? Quote Link to comment Share on other sites More sharing options...
babadono Posted September 16, 2020 Share Posted September 16, 2020 But still with the lifted ground? Quote Link to comment Share on other sites More sharing options...
babadono Posted September 16, 2020 Share Posted September 16, 2020 Sounds like a ground loop to me. Quote Link to comment Share on other sites More sharing options...
babadono Posted September 16, 2020 Share Posted September 16, 2020 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. Quote Link to comment Share on other sites More sharing options...
babadono Posted September 16, 2020 Share Posted September 16, 2020 Theories? Here ya go: https://centralindianaaes.files.wordpress.com/2012/09/indy-aes-2012-seminar-w-notes-v1-0.pdf Quote Link to comment Share on other sites More sharing options...
JohnW Posted September 16, 2020 Author Share Posted September 16, 2020 5 hours ago, Thaddeus Smith said: But what else have you added/changed to the house as a whole? Literally nothing. Quote Link to comment Share on other sites More sharing options...
JohnW Posted September 16, 2020 Author Share Posted September 16, 2020 5 hours ago, babadono said: But still with the lifted ground? No, the ground lifter got rid of it. Quote Link to comment Share on other sites More sharing options...
babadono Posted September 16, 2020 Share Posted September 16, 2020 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. Quote Link to comment Share on other sites More sharing options...
JohnW Posted September 17, 2020 Author Share Posted September 17, 2020 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. Quote Link to comment Share on other sites More sharing options...
babadono Posted September 17, 2020 Share Posted September 17, 2020 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? Quote Link to comment Share on other sites More sharing options...
JohnW Posted September 17, 2020 Author Share Posted September 17, 2020 (edited) 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 September 17, 2020 by JohnW Quote Link to comment Share on other sites More sharing options...
babadono Posted September 17, 2020 Share Posted September 17, 2020 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. Quote Link to comment Share on other sites More sharing options...
JohnW Posted September 17, 2020 Author Share Posted September 17, 2020 Sorry, I only made it in about 80 pages. You know, life intrudes. Quote Link to comment Share on other sites More sharing options...
babadono Posted September 18, 2020 Share Posted September 18, 2020 Yea life, I get it. I should have pointed to page 101 when I first posted. Quote Link to comment Share on other sites More sharing options...
JohnW Posted September 18, 2020 Author Share Posted September 18, 2020 Problem solved. https://www.amazon.com/gp/product/B000K50HJE/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1 Quote Link to comment Share on other sites More sharing options...
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