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Gold AC powered deja vibe cauing huge hum

TheArchitect

Member
Joined
Jul 6, 2003
Messages
490
Just wrapping up a new pedal board build and I have an issue. Generally all is well but the board is causing a huge hum in the audio. The pedals are all powered by 2 PP2+ units with 3-4 2-1 adapters to get juice to everything with the exception of my MXR 10 band EQ and my Gold AC powered deja vibe. The 18v wart, the Deja Vibe and the two PP2+ units all plug into a common power strip

The pedal board does not even have to be plugged into the amp. Simply pluging the board onto the AC causes the issue. Unplugging the power to the deja vibe or unplugging the cable from the Deja Vibe output jack kills the hum.

Seems like a ground loop but I don't know how to safely resolve that. The 3-2 ground lift adapters may fix it but I don't want to be the ground path if something fails.... Any idea on how to fix this?
__________________
 

Wally

Well-known member
Joined
Feb 27, 2003
Messages
3,433
Does the hum occur if you use only the Deja Vibe into the amp? If so, a partial ground lift can be installed in the Deja Vibe. This would break the ground loop.
THe hum that occurs even when the pedal board in its entirety is fired up but not plugged into the amp is interesting. IF you go through the details in the first paragraph and quiten the noise issue down in that simple arrangment----or if there is no ground loop when using only the Deja Vibe, then see what happens when you reinstate the DV in the pedal chain. You may have one problem, you may have two problems. The question is...where is the problem. Separating the DV from the rest of the pedal chain lets you get closer to understanding where the problem/s is/are.
 

dtw576

New member
Joined
Feb 23, 2003
Messages
1,934
Depending on which DV you are using, you may need more mA or perhaps only use 9V. I had a Fulltone Mini DV and it was a 9V pedal and needed some serious mA IIRC. Was a long time ago but just wondering. I'm not familiar with the Gold AC cable but that has me suspecting your DV is 110-120V AC powered? Is that an old original DV? Perhaps one of the components is shot? I hate hunting down something like this to only find a bad cap in the circuit somewhere. Never dealt with Xindak stuff before but looks interesting.
 
Last edited:

TheArchitect

Member
Joined
Jul 6, 2003
Messages
490
Does the hum occur if you use only the Deja Vibe into the amp? If so, a partial ground lift can be installed in the Deja Vibe. This would break the ground loop.
THe hum that occurs even when the pedal board in its entirety is fired up but not plugged into the amp is interesting. IF you go through the details in the first paragraph and quiten the noise issue down in that simple arrangment----or if there is no ground loop when using only the Deja Vibe, then see what happens when you reinstate the DV in the pedal chain. You may have one problem, you may have two problems. The question is...where is the problem. Separating the DV from the rest of the pedal chain lets you get closer to understanding where the problem/s is/are.

After some experimenting the fix was pretty simple.

Originally I had the amp in the top socket of the wall outlet and the pedal board in the bottom socket. In my mind that was a single common ground. Hummed like mad. In retrospect I think I understand why that failed

Plugging the pedalboard into the same power strip as the amp seems to have solved the issue
 

TheArchitect

Member
Joined
Jul 6, 2003
Messages
490
Depending on which DV you are using, you may need more mA or perhaps only use 9V. I had a Fulltone Mini DV and it was a 9V pedal and needed some serious mA IIRC. Was a long time ago but just wondering. I'm not familiar with the Gold AC cable but that has me suspecting your DV is 110-120V AC powered? Is that an old original DV? Perhaps one of the components is shot? I hate hunting down something like this to only find a bad cap in the circuit somewhere. Never dealt with Xindak stuff before but looks interesting.

Mine is AC powered
 

Wally

Well-known member
Joined
Feb 27, 2003
Messages
3,433
Architect, those little and inexpensive wall outlet testers are very helopful, ime. I never plug into an outlet unless I test it. The unit will tell you if the outlet is wired correctly....or if wired incorrectly, it will show you how it is incorrect. I have one outlet here in this buidlng that is wired with hot to neutral...soI don't use that for instruments/amplifiers.
Kudos on finding the problem.
 

TheArchitect

Member
Joined
Jul 6, 2003
Messages
490
Architect, those little and inexpensive wall outlet testers are very helopful, ime. I never plug into an outlet unless I test it. The unit will tell you if the outlet is wired correctly....or if wired incorrectly, it will show you how it is incorrect. I have one outlet here in this buidlng that is wired with hot to neutral...soI don't use that for instruments/amplifiers.
Kudos on finding the problem.

Thanks. Pretty sure they all tested as wired correctly when they were installed though. Will have to double check them
 

Wally

Well-known member
Joined
Feb 27, 2003
Messages
3,433
Okay....so you went from having a groundloop hum with the pedalboard and the amp plugged into the same outlet...two females on the outlet.....to plugging the pedalbaord and the amp into one common power strip, right?
I may bemissing something, but I am thinking that if the wall outlets are wired correctly, then the power strip has a partial ground lift circuit in it that is preventing the ground loop from occurring. IF not, then you haven't changed anything by using a power strip for both the amp and the pedalboard compared to using two correctly wired outlets. So, I am still not convinced that the outlets are wired correctly unless the power strip has the partial ground lift......but again...kudos on getting rid of the noise.
 

TheArchitect

Member
Joined
Jul 6, 2003
Messages
490
Okay....so you went from having a groundloop hum with the pedalboard and the amp plugged into the same outlet...two females on the outlet.....to plugging the pedalbaord and the amp into one common power strip, right?
I may bemissing something, but I am thinking that if the wall outlets are wired correctly, then the power strip has a partial ground lift circuit in it that is preventing the ground loop from occurring. IF not, then you haven't changed anything by using a power strip for both the amp and the pedalboard compared to using two correctly wired outlets. So, I am still not convinced that the outlets are wired correctly unless the power strip has the partial ground lift......but again...kudos on getting rid of the noise.

I am inclined to agree but I have not had time to figure out the why yet, just the what.
 
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