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First Post, Question on GCX

Posted: Thu Oct 22, 2009 7:15 pm
by Radiohead

I am hoping someone can help me with an issue I am having with my GCX Switcher.

I am getting an uncontrollable squeeling on my ENGL PreAMP.
My set-up is as follows:

Loop 1 - EQ
Loop 2 - Wah
Loop 3 - Rust Driver
Loop 4 - OCD
Loop 5 - Wampler
Loop 6 - Phase
Loop 7 - ENGL 530e PreAmp
Loop 8 - ADA - MPI PreAmp
G-Major II (L & R Out)
BBE (L & R)
Mesa 20:20

When I turn up the volume on the ENGL so that the input meter on the G-Major is peaking adequately it squeels. At first I thought that something was wrong with the ENGL and I replaced the tubes. I realized that the ENGL was fine when I by-passes the GCX and went straight into the 20:20. I dimed the ENGL and no squeeling at all. Just Tone Heaven. Put it back into the GCX and just about blew my ears at the volume of the SQUEEL.

Has anyone come across this or have any suggestions?

Re: First Post, Question on GCX

Posted: Thu Oct 22, 2009 8:57 pm
by JohnClark
It is likely a routing problem causing the squeal. Rather than switching the preamps as if they were just two more effect boxes, you should use one GCX loop to A/B the outputs of the preamps.

1a. (optional) Loop 7 can be used for another pedal effect.
1b. Connect a Y Cable from the output of loop 6 (or 7 if another pedal is added) into the guitar inputs of both preamps.
2. Connect the output of the first preamp to the In of Loop 8.
3. Connect the output of the second preamp to the Return of Loop 8.
4. Connect the output of Loop 8 to the input of the G-Major2.

Loop 8 will now act as an A/B switch between the preamps, and should stop the squeal. Let us know how it works out.

Re: First Post, Question on GCX

Posted: Sun Nov 01, 2009 7:02 am
by Radiohead
John Clark,

Thanks for your help. Spitting the signal and running hot into the front of each pre-amp, using the GCX to control the switching on the return works great.

Can someone recommend a product to split the signal? I have 3 preamps. I want to leave the splitter in the back of the rack and forget about it. I do not want noise or grnd hums. I want to keep my sustain and interaction between the amp and guitar.

I purchased the Voodoo Labs Amp Switcher and it works great. The issue I have is that when I power off, next time I power on I need to select each of the 4 amps select bottoms every time. I guess the switches are electronic not mechanical?

Anyway, If there is a way to leave all switches open all the time (powering on and off) I am really happy with the product.

Re: First Post, Question on GCX

Posted: Tue Nov 03, 2009 5:03 pm
by JohnClark
A mod like that just may require a fine bottle of Tequila be sent my way if someone were really interested in it. ;)