My Decimator G string is humming - ground loop?

I had a ground loop with the Decimator G-String and the G-System - no matter what AC supply I had it on. Had to put an ISO transformer between the guitar out and the G-System input.

Last edited by Laird_Williams (2012-01-26 22:53:47)

Same thing here, ground loop caused by the G-string. Connecting the Ebtech HE in the "standard" way for 4cm solved this for me.
insert send > HE ch2 > amp in
fx loop send > Gstring gate in > insert return
output GS > HE ch1 > fx loop return

Well it's ground loop hum vs noise in your signal chain that's amplified in the preamp. AFAIK two different things and the G-string can correct only the latter.
Laird will be able to explain this a million times better.

Ground loops are REALLY odd buggers and can crop up in all kinds of weird places. It is not the pedal that is "adding" the noise. Nor is it the G. It is the combination of their grounding designs and the fact that their respective ground circuits are connected by a cable shield.

To test whether it really is a ground loop try this - run the pedal off a battery instead of the AC. Does the noise go away?

Last edited by Laird_Williams (2012-01-27 16:07:16)

Thanks cosmic,

Out of sheer curiosity, I tried the ebtech between the guitar out, and g in, and also between the amp send and g return.

I got even worse (strange) interference / noise with the ebtech in these positions - I tried two he2 units - so I don't think its a fault with the unit.

I'll try a battery shortly.

Yup - can confirm that, deffinately doesn't work

Laird - can you tell me how your hooked up?

If I've translated correct your in a loop allowing to engauge/disenguage the decinator?

I hope the battery helps and keep my fingers crossed. Hum can be a pain in the a**. I see you have got two HEs. In case a battery does not help, you could try to consequently put the used amp inputs and outputs through the HE all at once and see what happens. Have you tried this before or did you put the HE here and there into one connection at a time? Do you want to shortly describe your setup?

"My high gain channel is noisy" is the common refrain. The problem is, unless it is really poorly designed...the hight gain channel is NOT what is noisy. What the high gain channel usually does is take an almost-inaudible amount of noise at the amp input and apply lots of distortion, compression, and gain to it so that when that noise comes out, it is obnoxious.

So the logical thing to do is to cut the noise off BEFORE it enters the amp in the first place. This helps a lot of things:
1) If you don't have something like the G-string, and hence have to have the detector and gate in the same place in the signal chain, it helps the detector be more accurate about when you are playing and when you are not. Gate detector circuits like a nice, clean, pristine signal. Having the detector as close to the guitar as possible in the signal chain helps it make MUCH better decisions about when you are playing and when you are not.
2) It lets you use a much lighter touch with the thresholds and damping parameters of the gate. This means that the gate will be able to accurately handle a wider range of playing dynamics than it would if used post-gain.

Generally - the best way to use a gate is
1) To attack noise and eliminate it without the gate in every way possible.
2) Place the gate as close as is practical (and effective) to the guitar signal.

So - how am I hooked up?

Guitar --> Lehle Sunday Driver In
Lehle Sunday Driver Out --> G-String Guitar In
G-String Guitar Out --> Ebtech HE2 channel 1 In
Ebtech HE-2 Channel 1 Out --> G-System In

G-System Loop 4 Send --> G-String Decimator In
G-String Decimator Out --> G-System Loop 4 Return

G-System Insert Send --> EbTech HE-8 Channel 1 In
Ebtech HE-8 Channel 1 Out --> (pre) Amp In
Preamp out --> Ebtech HE-8 Channel 2 In
EbTech HE-8 channel 2 out --> Power Amp In
Power Amp Speaker Out --> Load/Cab Sim In
Load/Cab Sim Out --> Ebtech HE-8 Channel 3 In
Ebtech HE-8 Channel 3 Out --> G-System Insert Return

G-System Out/L --> Ebtech HE-8 Channel 4 In
EbTech HE-8 Channel 4 Out --> Console

G-System Out/R --> Ebtech HE-8 Channel 5 In
EbTech HE-8 Channel 5 Out --> Console

My rig is whisper quiet. I bypass loop 4 90% of the time because i don't need the gate for those presets
One the 10% of the time that i do need the gate, I engage loop 4 and all is well.