Need GCX and hum/connections help...........

[choadyjpm]

I have a GCX and am trying to use it basically as an amp switcher. I'm switching between a Soldano SLO100 head and a combo of Mesa Triaxis/2:90/Lexicon MPX G2 effects. I wanna run it so that the Soldano goes to one cab and the Mesa stuff to another and be able to control each seperately to either play one or the other and play outta both at the same time. I followed the directions that came with the GCX and, although not really in depth, I was able to get it to work. But I have some major hum problems. Let me get the details out there just so you guys know....

My GCX is old. I got it when it was still Digital Music Corp, like right before it became Voodoo Lab owned so I don't have the Voodoo Lab logo on mine. I don't know how the GCX has changed since then if at all feature-wise or I/O's.

My Triaxis and 2:90 are from around 1999 or so. I noticed that the new 2:90 pwer amps have a ground/lift switch like the Triaxis does but my 2:90 doesn't, although my Triaxis does. Hope that doesn't cause a problem in the battle with killing hum. And my Soldano has no ground/lift switch either. They all have three prong power connectors all plugged into my Furman Power Conditioner.

Since I got it to switch the way I want, it seems to probably be a cable issue maybe. I'm not right next to my rig but I think I have it hooked up the way it says in the manual about Combining Multiple Amps, but it looks like there may be a Y Cable involved where I used two cables in the back utilizing both the guitar Out and Feed Thru. The loops work, but are noisy, and when I turn off both loops, the cab powered by the Soldano hums LOUD. My cables are noisy too I have found out (Planet Waves Cable station with the solderless system of making cables). What cables would I need to get or what do you recommend? Any help with this would be GREATLY appreciated! I'm gonna be back with my rig tomorrow so I will be able to give more details and may call support if it helps and come back on here too to be more in depth. Thanks in advance!!!!!


Cody

[Josh Fiden]

The GCX you have is not significantly different than the current version. The only changes were improvements to the guitar input/buffer. Incidentally, there was never any ownership change. Digital Music and Voodoo Lab have always been the same company.

The solderless cables can be a problem if you don't assemble them very carefully. It's hard to beat soldered on connectors for reliability, but I know a lot of people have good success with the solderless type.

A good first step would be for you to draw a rig diagram like the ones we have posted on the GCX product page. Here's a blank form to use:

http://www.voodoolab.com/gcxdiagrams/bl ... heet_p.pdf

Please post how you have it wired and we'll look at it from there!

Thanks for participating in the forum.

Josh Fiden
Founder / CEO

[choadyjpm]

Sorry I didn't know how to modify a .pdf or print out and scan the diagram, but here is how I have it set up so far....

*Guitar plugged into Guitar In on the GCX front panel
*Rear panel Guitar Out into Loop 1 In
*Soldano input into Loop 1 Send

(Mesa Triaxis/2:90 & Lexicon wired to work together as a "head", so no Lexicon to Soldano)

*GCX rear panel Feed Thru into Loop 2 In (which I think could be wrong cuz that's what is making the most noise, like something is unplugged)
*Lexicon Guitar In (rear panel) into Loop 2 Send

That's basically what I've got so far. I referenced the manual on combining amps on page 9, but it says Audio In and does a Y looking thing into both Loop 1 & 2 In's. Does that imply the need for a Y-cable or could I use the Feed Thru? I want it set up so I can turn the amps on and off or combine them both like the example in the manual. I called VoodooLab today but John the GCX guy cut out early today so no help until Monday

[Josh Fiden]

That's all wired correctly. This is most likely a ground loop, although a bad cable could cause the same problem. Let's see if we can figure it out...

1. Does the hum come from both amps or just one? Which one?
2. Do they only hum with the loop turned on, or also with the loop off?
3. Unplug the cable from loop#1 send to Soldano. Does the Mesa still hum?

If the Mesa hums without the Soldano connected, leave that cable off. Otherwise plug it back in.

4. Unplug the 2 cables from GCX guitar out and feed thru out into loops 1 & 2 inputs. Plug your guitar directly into each loop input and turn on only that loop. Does it hum?

That should be some good info to get started! Post what happens and we'll take it from there.

Thanks!
Josh Fiden
Founder / CEO

[choadyjpm]

That's all wired correctly. This is most likely a ground loop, although a bad cable could cause the same problem. Let's see if we can figure it out...

1. Does the hum come from both amps or just one? Which one?
2. Do they only hum with the loop turned on, or also with the loop off?
3. Unplug the cable from loop#1 send to Soldano. Does the Mesa still hum?

If the Mesa hums without the Soldano connected, leave that cable off. Otherwise plug it back in.

4. Unplug the 2 cables from GCX guitar out and feed thru out into loops 1 & 2 inputs. Plug your guitar directly into each loop input and turn on only that loop. Does it hum?

That should be some good info to get started! Post what happens and we'll take it from there.

Thanks!
Josh Fiden
Founder / CEO

So I'm still working on my rig. I took a break from it and was playing through just Triaxis but now I'm back trying to battle the hum again Here is what happened when I followed your steps....

1. Does the hum come from both amps or just one? Which one? At first I thought it was just Soldano but I forgot I had a light noise gate on my FX processor so I disabled that and noticed both amps were humming equally as much.

2. Do they only hum with the loop turned on, or also with the loop off? They hum both with loops on and off.

3. Unplug the cable from loop#1 send to Soldano. Does the Mesa still hum? No it stopped.

4. Unplug the 2 cables from GCX guitar out and feed thru out into loops 1 & 2 inputs. Plug your guitar directly into each loop input and turn on only that loop. Does it hum? I removed said cables from the equation and plugged directly into the loop inputs. Both amps ran almost completely hum-free (I could only hear a SUPER TINY amount of hum but that was listening with "dog ears", but when I rolled my volume knob all the way down on my guitar, the hum was completely gone! Success).

A slight update to the setup wiring is that I dedicated Loop 8 to channel switching on my Soldano (only wiring to GCX that isn't a Planet Waves Cable Station cable since I ran out of plugs.) Basically the way I've been getting by right now is adjusting the noise gate on my FX (more gate to null the hum) and when I switch to Triaxis I have Loop 8 activate the clean on Soldano to "silence" it to some degree. Soldano clean is like a 3/10 on hum scale while Soldano distortion is about a 9/10! Ugh. Oh and one other observation I made while going through the steps was when I unplugged some cables from the GCX, I could hear them hum like crazy when they passed by, in close proximity, to the power cords of the 2:90 and Triaxis. I can't remember which cable it was, but when I unplugged it, I just moved it around the other cables and cords and that was the observation I made. Perhaps I need to isolate the power cords from Triaxis/2:90 better cuz right now I basically have them plugged in and I coiled up the excess and tried to tuck it into the side or back as neatly as I could. Remember, Triaxis has ground/lift switch but my 2:90 is old and has no such switch.

Thanks for taking the time to write out these steps and for your help, Josh! I'm gonna be the happiest dude ever once I get this ironed out. My band is booking shows this month (our first shows) and my tone rules but I'm scared to death about the hum. Thanks again!!!


Cody