Ground Issue; I have tried all the mentioned methods.

L

lolzgreg

Member
I put together my Rack Gizmo controlled switching rig today. I am using an EVH 5150 III with the rig.

The issue I'm having is: Whenever I turn any effect on in the effects loop of the amp, I'm getting insanely loud ground hum.

I have the effects hooked up all in inserts 5-8; one pedal, my ISP Decimator G-String, is both in front of the amp and in the loop.

The pedal in front of the amp do not have the hum issue. This leads me to thing there is a ground loop in the effects loop portion.

I am using a Voodoo Labs PP2+

This is what I can say about my problem.

-I tested all of my cables through a guitar amp prior to hooking them up, and everything works without a doubt, and no leads are reversed, nor are there any poor connections.
-I tried lifting the ground on one side of the cable going from the effect return of the amp to the Rack Gizmo OUT 8/NO ; it did not work.
-I tried lifting the ground on one side of the cable going from the Rack Gizmo In 5 to the amp's effect send; it did not work.
-I tried pressing the ground lift on the back of the Rack Gizmo; it did not work.
-I tried moving the unit in the rack case/floating it with my hands to make sure it wasn't a rack ground issue; it was not.
-By turning the power off to a pedal while the respective loop was on in the effects loop, the noise went away
-The hum is not minor, but so loud the amp would be unplayable

If you have any suggestions, it would be very very welcome. Thanks again for the great support.

Cheers,

Greg
 
You only get hum when a Rack Gizmo loop is on, and when all loops are off, it's fine? That's pretty unusual.

Is the hum actually identical when you turn on any of loops 5-8?

If the answers to above are yes, then unplug one pedal at a time from the Rack Gizmo and see if you can get the hum to go away. Start with the G-String, because of the way it's connected, it's likely to cause a ground loop. (The ProRack G has ground lift switches for this reason, but unfortunately the Decimator does not).
 
Ron,

EDIT: MOST of problem solved; I'm still getting ground noise when I turn the Decimator on, and it figures, because it's in the loop AND in front of the amp.

As I turn the threshold up, the hum makes its entrance.

Do you have any recommendations to stop the ground noise from the Decmator?

I do have a question regarding the tuner now though. As per your recommendation, I set things up like this, and it works great:

It's pretty easy to do - you just need to run the loops out of order. Since you need more loops in the amp's effects loop, use loops 1-5 for that (since 1-4 are grouped together), and use 6 and 7 or 7 and 8 for the effects in front.

For example:

Guitar into loop 7 input
Loop 7 output into loop 8 input
Loop 8 output to front of amp

Amp's loop send into In 1-4
Out 1-4 to In 5
Out 5 to amp's loop return

Connect effects to loop sends/returns as required


However, I don't know how I'm going to do this tuner mute option now. I used to have it on loop number 4, so when I switched to that empty loop, it would mute.

Your support has been fantastic.

Cheers!
 
Okay, you'll need one to three ground lifted cables for the Decimator. Like before, start with the last cable in the signal path (the 2nd output of the Decimator), use a ground lifted cable there. If that's not enough, use a second one for the 2nd input of the Decimator. If it's still not enough, use a third ground lifted cable for the 1st output of the Decimator. Somewhere along the line, the hum should go away.

To get tuner mute, get loop 6 into the game:

Amp's loop send into In 1-4
Out 1-4 to In 5
Out 5 to In 6
Shorting plug in loop 6 return
Out 6 to amp's loop return
(Signal will be muted when loop 6 is ON)

...or...


Amp's loop send into In 1-4
Out 1-4 to In 5
Out 5 to In 6
Send 6 to amp's loop return
(Signal will be muted when loop 6 is OFF)
 
Ron,

You are the man.

I think I'm only going to need two ground lifted cables.

I have one of these for my reamping rig: http://www.sweetwater.com/store/detail/HumXLR/

I connected it to the effects loop only section and it solved the issue.

I suppose if I break ground on two, I'll be a winner.

Now when I figure out how to stop my popping pedals, I'll be golden. This forum is the best.
 
Ron,

I think I'm losing it.

I've got the shorting plug thing down, tuner mute is great.

I defeated the grounds on those two cables and now the noise is WORSE. However, using the Ebtech Hum Eliminator, it solved the problem.

I think I'm just going to need that unit.
 
New update:

The ebtech unit only fixed PART of the problem. I think I'm going to abandon the idea of the G-String in the loop. I've tried everything and I can't get rid of the hum.

With it just in front its quiet, but then I get beautiful preamp hiss and noise. It's better to live with that than ground hum in my opinion. It just lurks underneath all your notes and makes them sound distorted.
 
NEWER UPDATE!

By gee, I've got it.

I put the Hum Eliminator in the effects loop (between the send and return). BAM!

I am noise free.

WOO HOO!

Thanks again, Ron!
 
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