Hum with Active Volume Pedal***RESOLVED***

David Ball · From: North Carolina High Country

Maybe someone can help me here. I'm fighting a low level hum that's driving me crazy. I've narrowed it down to the volume pedal, but I'm not sure exactly where to go from here. Here's the deal--I have a Telonics and a Hilton pedal, and if either of those are plugged into any of my amps, I get hum. I can unplug the wall wart for the pedal, and the hum goes away. I can replace the active pedal with an Ernie Ball passive pedal, and the hum goes away. I can unplug the guitar from the pedal, and the hum (or lack of hum with the EB) doesn't change.

In each case, nothing is changed except the volume pedal itself. I'm using George L cable, and I've tried several of those just to be sure. Since the hum goes away with either the unplugging of the wall wart or changing to the EB pedal, I don't think there's a cable problem anyway.

Any ideas?

Thanks,
Dave

Lynn Oliver · From: Redmond, Washington USA * R.I.P.

You could try plugging into an ebtech HumX. I plug my amp into a HumX and everything else goes straight into the surge suppressor.

Earnest Bovine · From: Los Angeles CA USA

Is there a guitar plugged in, or just a pedal?

David Ball · From: North Carolina High Country

Lynn, I've not tried a HumX--I tried a power line filter that I had sitting around for computer purposes, but I doubt it would do the same thing. Something like this might be the ticket though--I tried plugging the amp end of the cable into my PodXT and listened through the headphone with all the effects bypassed, and no hum. I also tried using the less hot input on my Fender, and decreasing the sensitivity on the Webb and both of these reduced the hum greatly. I tried the ART Cleanbox that has always done the trick for me with ground loops in the past, but this didn't make any difference. I think I'll pick up a HumX and see what happens.

Earnest, I've tried it both ways with guitar plugged in or just the pedal. It's the same either way.

Thanks guys!

Dave

Scott Swartz · From: St. Louis, MO

Here is the theory behind your problem

http://www.jensen-transformers.com/an/an004.pdf

The solution is a 1:1 transformer isolation box such as the Jensen Iso Max or various other companies make them also.
_________________
Scott Swartz
Steeltronics - Steel Guitar Pickups
www.steeltronics.com

David Ball · From: North Carolina High Country

That's how the ART Cleanbox works--1:1 isolation transformer. That's always cleaned things up in the past, but didn't this time. I can't really explain why...

Carl Williams · From: Oklahoma

PM sent David...Carl

David Ball · From: North Carolina High Country

Thanks Carl!

Dave Beaty · From: Mesa, Arizona, USA

Hi David,
We had an engineering meeting regarding your post this morning. The specific condition/problem you described is something we have not encountered, but we have seen similar interconnecting ground loop problems - which in every case, were ultimately resolved satisfactorily. I have sent you a more in-depth series of thoughts and suggestions by email.
Dave

Ken Fox · From: Nashville GA USA

Another often overlooked ground loop is one that can be created when the pedal is attached to the pedal bar, thus grounding the pedal to the guitar's ground plane

Ken Fox · From: Nashville GA USA

delete

David Ball · From: North Carolina High Country

Charlie Powell · From: Kingsport, Tennessee, USA

I have this problem when I use my Hilton pedal, particularly if I am using one of my tube amps. I tried all combinations of my George L cables to no avail. Then I unplugged the George Ls and used good quality regular instrument cables with soldered on plugs. That did it. No more hum. If I am using a pot pedal, either cables work fine with no hum.
_________________
Charlie Powell

David Ball · From: North Carolina High Country

OK Problem resolved. Here's what I did. In place of the ART Cleanbox, I used the "isolate" function on my Radial Big Shot AB switch. Both devices use a transformer and some additional circuitry--the Radial has a little electrolytic cap in the circuit, but I haven't traced down the circuit from the PCB. At any rate, although the ART has done great at getting rid of ground loops at line level signals, it doesn't seem to do so well when the signal is lower amplitude. Using the Isolate switch on the Radial, and bingo--hum gone.

Thanks everyone for the suggestions. Life is good and hum free now!

Dave

Jerry Overstreet · From: Louisville Ky

Are you guys saying that a/c powered active volume pedals actually induce hum into an otherwise quiet system?

If that is the case, it certainly doesn't make a good selling point for them.

I would expect that would be the first thing mfgs. would address before offering them for sale if so.

Or is it the effect of ganging several electrical connections to a single source?

David Ball · From: North Carolina High Country

The active pedal didn't induce hum, but a ground loop through the pedal did. Both active pedals I have are extremely quiet--quieter than a pot pedal once the ground loop is gone. Especially through long cables.

In my case, it was how everything was plugged together into the AC lines, and not the pedal at fault.

Dave

John Billings · From: Ohio, USA

I had a stereo, active Goodrich pedal that did the same thing. It was okay for gigging, but not in studios. Engineer at the studio I first tried to use it at said, "JB, there's a hum." I tried everything I could think of, but not wanting to waste much studio time, I pulled out my old standby ShoBud pedal that I got in '72. The engineer said, "Hum's gone. Guitar sounds much better too."

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