# Ground loop isolator



## willis7469 (Jan 31, 2014)

So I picked up one of these, and installed it. Can anyone figure out why it made my 60hz hum louder? Like 10db louder. Could the ends be installed on the wrong side?










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## Talley (Dec 8, 2010)

pretty sure that is just a glorified resistor between the two sides.

Today my noise is completely gone... I mean completely. amp on/off, volume up/down, disc paused etc... it don't matter. it's completely gone with ear all the way pressed to any speaker driver woofer tweeter anything....

but yesterday there was a slight hiss from midrange. This tells me I just need to get an isolation transformer for my system.... it's gotta be picking up noise from who knows where. You need a common ground and isolated power.

is all of your equipment supplied with 3 prong IEC outlets on the equipment? Your using RCA.. any chance for xlr? I'm using RCA too so it is possible to eliminate it all. But I have a commond ground that is isolated from the house which helped.


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## willis7469 (Jan 31, 2014)

Hey talley. I should have been more clear. This is for my subs. I barely experimented with this thing last night, but when I hooked it up just before the sub amp(on 2 subs at different times, not the 3rd) it made the hum at least 10db louder. So to answer the xlr question, no. All 3 subs are 2 prong. One is on different circuit, I think the other 2 share. Can't recall. 


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## Talley (Dec 8, 2010)

willis7469 said:


> Hey talley. I should have been more clear. This is for my subs. I barely experimented with this thing last night, but when I hooked it up just before the sub amp(on 2 subs at different times, not the 3rd) it made the hum at least 10db louder. So to answer the xlr question, no. All 3 subs are 2 prong. One is on different circuit, I think the other 2 share. Can't recall.
> 
> 
> Sent from my iPhone using Tapatalk


Sorry I didn't know it was on the subs. Is there any direction labeling on that thing for the signal?

you could take a piece of copper wire and loosed a screw on each amp plate and run the wire between all three so it bonds all chassis together and then run that groudn wire to the center screw on the outlets. I know this sounds a bit "crude" but it's just for testing.

Since you got two different circuits you wanna bond that ground between them with something like a 12g wire. this should elminate the ground buzz... but as always I could be wrong. but it couldn't hurt to try.


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## willis7469 (Jan 31, 2014)

Good idea. I have miles of wire. I just have to get the house to myself. I ran a piece from my avr chassis to the recepticle it's plugged into a while back. I felt so nerdy. Lol. 
I tried the isolator at the sub out and it really helped. BUT, it killed my lfe by 10db. (I did a quick level check). So it's gone now...


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## RBTO (Jan 27, 2010)

willis7469 said:


> So I picked up one of these, and installed it. Can anyone figure out why it made my 60hz hum louder? Like 10db louder. Could the ends be installed on the wrong side?
> 
> 
> Sent from my iPhone using Tapatalk


These devices are a transformer and if they are located anywhere near a 60Hz magnetic field (power transformers, etc.), they do well at picking up hum of their own. Be sure not to locate the hum isolator near any power lines or electrical equipment. Your subwoofer is more sensitive to 60Hz than your other loudspeakers so any 60Hz going to it will be apparent at once.

Hook the isolator to your sub with the input shorted and see if you get any hum (you shouldn't). If you do, move the isolator around to see if you can reduce or change the amount. If so, there's something making a 60Hz magnetic field nearby. If you don't get any hum until you connect your source, chances are, you might have a broken shield in the input cable or a problem in the source.

Also be sure your center pin AND outer shell connect. If there's a break in the shield, all kinds of hum will be introduced.


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## hksoundpro (Aug 7, 2012)

Transformers such as these have been in use for car audio, for a very long time!
Typically, it's a 1.4:1 transformer, which may or may not have electrolytic caps and/or resistors in the circuit.
As mentioned by RBTO, they can be sensitive to radiated AC. The cylindrical housing can be, in the case of better quality items, Mu metal. Judging by the look of the RCA cables/connectors, this is not an especially high-grade device. 
Signal polarity is a frequent problem with these isolators, as they tend to be hastily produced with little or no QC, so do take care. They're easy to open, so it's simple to check for polarity issues, poor solder joints or cable abrasion, all of which could be contributing to your increased 60hz hum.


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## willis7469 (Jan 31, 2014)

Thanks guys. I haven't intentionally left this cod, or not responded. I've had some family things to handle. And I haven't played with the isolator much, so no disrespect. I tried some of the things you mentioned with no changes. One way I did get a different kind of result was hooking it up to the avr. It killed my output globally by about 10db. All 3 subs are fed by a bfd so that explains something. Not sure what though since the hum is louder when I go direct to the sub amp, but output is gone by going to the avr. As mentioned, this is not an expensive or super high quality device. Next I will open it up and see what's inside. I feel like the ends were put on wrong. 


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## MikeTz (Jan 14, 2016)

I'm not sure what your system configuration is but a common source of hum in theater systems is from the CATV system. If you are using a CATV system try unplugging the coaxial input at the wall and determining if that eliminates the hum in your subwoofer. If it does, then go online and search for an in-line coaxial CATV ground loop isolator and you should be all set. There are several good choices.


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