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Post subject: Ground Loop Problem
Posted: Thu Apr 18, 2013 10:25 pm
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Just wondering if any of you folks have run into a hum problem, with a stand alone reverb unit. Thought the noise was from the amp. But after some ground rearrangements in the Bassman, it's way quiet. Hook up the reverb unit, and the hum is very noticable. If I'm playing, it isn't a problem. But at idle it's a drag. I know,"Don't worry 'bout no stinkin' noise just play that thing"!!! Any way if you guys have any advice, I could dig it. Art

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Post subject: Re: Ground Loop Problem
Posted: Fri Apr 19, 2013 1:46 am
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If all of you gear have a 3 prong cord , you may need to isolate a ground from one or more units .
There are 3 prong to 2 prong adapter on the market for this use.


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Post subject: Re: Ground Loop Problem
Posted: Fri Apr 19, 2013 5:47 am
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I agree with Stratele. And have the three-to-two AC adapter be reversible. So that you can flip the plug over. Just means that the polarity of the wiring on one unit is 180-degree from the other unit. This sometimes causes an additive effect, instead of cancellation of AC hum riding on the green ground wire.


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Post subject: Re: Ground Loop Problem
Posted: Fri Apr 19, 2013 6:04 am
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Not trying to hijack ya Art however......

I was reading somewhere that even connecting two amps via an ABY box can cause ground loop problems ???
Someone had removed the third (ground) from the plug on my Traynor YRM-1 and I wondered if they did it to accommodate a multiple amp set up ?
obviously leaving me in jeopardy of shock when not plugged into the back of a grounded amp.

PS Tubes on the way 8)

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Post subject: Re: Ground Loop Problem
Posted: Fri Apr 19, 2013 6:15 am
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stratele52 wrote:
If all of you gear have a 3 prong cord , you may need to isolate a ground from one or more units .
There are 3 prong to 2 prong adapter on the market for this use.


Personally, I'd not be removing an essential safety connection rather than fix the actual cause of the hum, but maybe that's just me. ;) Certainly don't expect to play anywhere requiring safety tested gear if you do this, they'll not even let you near the stage.

If the gear comes from the factory with two mains wires, it's fine. If it has three, it needs three to keep you safe in case of problems - without the ground wire in place, it won't even trip an RCD until far too late, if at all.

A couple of decent guides for hunting down the dreaded ground loop issue without resorting to bodgery -

http://www.performing-musician.com/pm/d ... chspec.htm

http://www.soundonsound.com/sos/1994_ar ... loops.html


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Post subject: Re: Ground Loop Problem
Posted: Fri Apr 19, 2013 6:35 am
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Prolly didn't make this clear. If you use a cheater plug AND the hum drops with the Reverb Unit or whatever you are using --- in reverse position. You can try re-wiring the primary leads from the power tranny. The two black leads off the OEM power tranny, of most vintage Fender amps.

Be sure that the black wire of the power cord is going to the FUSE and POWER SWITCH. And the white wire is going to the tranny. This must be the wiring on both the amp and the stand-alone reverb unit --- or you can get a loop hum.

Sorry for the confusion. Really, if the hum only exists at idle. You might wish to let sleeping dogs lie. :D

http://www.webphix.com/schematic%20heav ... _schem.pdf


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Post subject: Re: Ground Loop Problem
Posted: Fri Apr 19, 2013 4:12 pm
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Excellent info, Vulpinity!! Appreciate all the advice you folks provided!!! Actually, I use those Hum-X caps at the outlet for each unit. Beemer, I think it's time for a filter cap up grade. Let you know if that helps. BTW The hum did increase over time. Art

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Post subject: Re: Ground Loop Problem
Posted: Fri Apr 19, 2013 8:27 pm
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Thanks Chris!!! How was the B- Day? Know what you mean about the A-B-Y boxes. Was thinkin' about using my Radial A-B-Y box. But it's not designed for this purpose. Looked over Radial Engineering's stuff. But from what I can see it's focused more along the lines of interfacing unbalanced to balanced apps. Oh Well, I'll give them a call. Any way, I've got to make sure the reverb amp is running as clean as possible. Art

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Post subject: Re: Ground Loop Problem
Posted: Sat Apr 20, 2013 11:15 am
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Thanks Art
The b-day was excellent !
My wife and kids always make me feel respected and loved !
I am a blessed man.

I know I'm the young guy here at 47 but dang I'm feeling it !

Tubes should be there today or Monday
Enjoy them, sure hope they are a tone improvement for you.

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Post subject: Re: Ground Loop Problem
Posted: Sat Apr 20, 2013 9:39 pm
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Outstanding Generosity, Chris!!! Super cool collection of 6SN7GT tubes!!! Tried a Sylvania and the RCA in the Valco. My Strat is kind of a dark sounding one. So with this amp,"BB King" is spoken here. BTW The Valco is housed in a 15-20yr seasoned pine cab, no tolex(16"w X 20"h X 9 1/2"d), very resonant. A 10" Weber alnico @8ohm, It's mate is also in a seperate pine cab with a 10" Weber alnico@8ohm(for a 4ohm load). Rebuilt and rewired the amp a couple of years ago. Just a great 5 watt guy. Thanks Again, Art

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Post subject: Re: Ground Loop Problem
Posted: Sat Apr 20, 2013 10:01 pm
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Just returning the kindness
Enjoy !

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2017 50's Baja Telecaster BSB

1968 Bandmaster with 2X12 cab C-rex speakers
VHT Special 6 Ultra combo

Visual Sound Route 66
Cmatmods Signa Drive


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