Lost channel when loop off

Q & A for building and interfacing your rack gear with Ground Control Pro and GCX-based systems.
bettsaj
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Lost channel when loop off

Post by bettsaj » Tue Oct 30, 2018 8:06 am

Hi, long time no see..........this is likely one for JohnClark however if anyone can spot any obvious issues with the wiring let me know.

i'm having trouble with my GCX. It's not the GCX that's at fault, of that i'm sure. I suspect it's the way its wired but I just can't get my head around it... Maybe a second set of eyes will help.

The below diagram is how my system is wired. The GCX is a full stereo system, all 8 loops. I've set it up so that only loops 7 & 8 are going through the Triaxis FX loop. My issue is this...... Every time i turn off loop 8 I lose a speaker cabinet. However when loop 8 is on i get both. What have i done wrong?

Also, I've put the mistress in the loop before the G-Force and it sounds bad, with like a whistling sound as the flanger effect modulates. I've tried it before the FX loop and it's not so bad, but still not as it should be. Any ideas?
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"My technique is laughable at times. I have developed a style of my own, I suppose, which creeps around. I'll never be a very fast guitar player."

David Gilmour

bettsaj
Posts: 234
Joined: Fri Jun 11, 2010 12:13 pm
Location: Darkest Suffolk UK
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Re: Lost channel when loop off

Post by bettsaj » Tue Oct 30, 2018 8:53 am

Just had a thought.... Could it be something to do with the Triaxis FX loop being on? When I turn off loop 8 on the GCX have i got to also turn off the loop on the Triaxis?
"My technique is laughable at times. I have developed a style of my own, I suppose, which creeps around. I'll never be a very fast guitar player."

David Gilmour

JohnClark
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Re: Lost channel when loop off

Post by JohnClark » Tue Oct 30, 2018 10:40 am

Are all cables standard mono Instrument cable?

You will need a somewhat custom made cable that i can only describe as being an "In-Line Y" with a Mono (TS) End that goes to a Stereo (TRS) end. The Tip from the Mono (TS) end will connect to both the Tip and Ring on the Stereo (TRS) End. The Sleeves simply connect together as always.
InLineY.jpg
InLineY.jpg (19.07 KiB) Viewed 2192 times
If whatever is in Loop 7 also has Stereo Outputs...
1. The cable between Triaxis FX Send and Loop 7 In need to be the "In-Line Y" cable.
2. The cable between Loop 7 Out and Loop 8 In needs to be full stereo.

If whatever is in Loop 7 has a Mono Output...
1. The cable between Loop 7 Out and Loop 8 In needs to be the "In-Line Y" cable.


This will allow the Mono FX Send to Drive both FX Returns when the GCX Loops are bypassed and the FX Loop is ON, which will result in all speakers firing.
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bettsaj
Posts: 234
Joined: Fri Jun 11, 2010 12:13 pm
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Re: Lost channel when loop off

Post by bettsaj » Tue Oct 30, 2018 11:06 am

Right, so if I understand you're saying this...

The mistress is a vintage mono pedal. So the output from loop 7 to the input of loop 8 needs to be a mono to stereo Y cable like the one you've drawn. No problem.... i should be able to knock one of those up in no time.

Does the cable need to be stereo cable or can I use standard mono cable but connect the tip and ring with an extra piece of wire?
"My technique is laughable at times. I have developed a style of my own, I suppose, which creeps around. I'll never be a very fast guitar player."

David Gilmour

bettsaj
Posts: 234
Joined: Fri Jun 11, 2010 12:13 pm
Location: Darkest Suffolk UK
Contact:

Re: Lost channel when loop off

Post by bettsaj » Tue Oct 30, 2018 11:18 am

I'm being stupid... If i use a stereo cable i'll just twist the tip and ring wires together on the mono jack end..
"My technique is laughable at times. I have developed a style of my own, I suppose, which creeps around. I'll never be a very fast guitar player."

David Gilmour

JohnClark
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Re: Lost channel when loop off

Post by JohnClark » Tue Oct 30, 2018 11:42 am

It can be wired using whichever cable you like... Mono cable is probably easier to work with ;)
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---------==Voodoo Lab Magician & Tech==---------

bettsaj
Posts: 234
Joined: Fri Jun 11, 2010 12:13 pm
Location: Darkest Suffolk UK
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Re: Lost channel when loop off

Post by bettsaj » Wed Oct 31, 2018 4:14 am

Ok, here's an update John.

I made a cable as you recommended, and now when loop 8 is off I get both channels, but when I engage loop 8 i get nothing, silence. Any ideas?
"My technique is laughable at times. I have developed a style of my own, I suppose, which creeps around. I'll never be a very fast guitar player."

David Gilmour

bettsaj
Posts: 234
Joined: Fri Jun 11, 2010 12:13 pm
Location: Darkest Suffolk UK
Contact:

Re: Lost channel when loop off

Post by bettsaj » Wed Oct 31, 2018 7:03 am

I'm going to try different cable... Although I checked for continuity it might be dodgy soldering
"My technique is laughable at times. I have developed a style of my own, I suppose, which creeps around. I'll never be a very fast guitar player."

David Gilmour

JohnClark
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Joined: Tue May 05, 2009 2:33 pm
Location: The Lab

Re: Lost channel when loop off

Post by JohnClark » Wed Oct 31, 2018 10:58 am

If signal passes when the Loop is OFF, that would suggest that the Cable to the Loop IN is OK as is the Cable from the Loop OUT... so the problem would likely be one of the cables connected to the Send and Return, or something with the effect unit itself.
When the Loop is ON, do the Level LEDs on the G-Force show any signs of life?

Let us know what you find!
------------------====Cheers!====------------------
Image
---------==Voodoo Lab Magician & Tech==---------

bettsaj
Posts: 234
Joined: Fri Jun 11, 2010 12:13 pm
Location: Darkest Suffolk UK
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Re: Lost channel when loop off

Post by bettsaj » Thu Nov 01, 2018 2:11 am

Hi John

When loop 8 is on, I get no sound, and also nothing on the input level indicators of the G-Force. As a thought, could it be that the cable from the send is a mono cable? As you probably know, the G-Force has 2 inputs, Left (Mono) and Right. I now have an "in line" Y cable between the output of loop 7 and input of loop 8, however the cable from the send of loop 8 is only mono and only going to the "Left (Mono)" input on the G-Force. Now I've added the "in line" cable, maybe I should use a proper stereo insert cable from the send to BOTH inputs of the G-Force? I should also then get both level indicators moving on the G-Force, instead of just the left hand one.

I've booked an 8 hour stint at the studio for Friday with the intention of spending the day programming. I can also use this time to play around with the wiring.
Attachments
tc_inputs.jpg
tc_inputs.jpg (27.13 KiB) Viewed 2162 times
"My technique is laughable at times. I have developed a style of my own, I suppose, which creeps around. I'll never be a very fast guitar player."

David Gilmour

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