GCX not passing audio

Q & A for building and interfacing your rack gear with Ground Control Pro and GCX-based systems.
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gerax
Posts: 35
Joined: Thu Jan 27, 2011 10:45 am

GCX not passing audio

Post by gerax » Fri Nov 11, 2011 1:39 pm

Hi all

I've purchased a first serie GCX (still labelled Digital Music Corp) to be used with my Ground Control (V 1.01).
I've hooked it up to my system but I have an issue with audio loops: everything seems to be connected right (I've checked both manuals) and is as follows: Guitar into front panel "Guitar in">Guitar Out on back panel to Loop In 1>Send to Amp in>FX Send from Amp>GCX Loop 1 Return> GCX Loop 1 out to amp FX Return. All I get is the sound of the Guitar straight to power amp, no distortion coming from the preamp, it seems that no matter what loop is enabled no audio is routed thru that loop.
I did this just as a test to verify the system's functionality.
Ground Control and GCX seem to communicate as they should, as I've saved a patch where loop 1 is active: the "Active" led and "Loop 1" on the GCX's front panel are correctly lit when I select that patch (I've also tried other loops, same result). Loops are set as "Normal", not as "Momentary".
I've tried with a simple stomp box in loop 1 (connected in the loop's send and return) and output of the loop going to the input of the amp: I get the straight amp tone (clean or distoretd) but no pedal even though it's active and the loop is selected.
I've tried other loops and combinations, but the result is always the same...as none of the 8 Loops is working.
My only doubt is that the GCX isn't the first device connected to the Ground Control as I don't have a wired 5 pin MIDI cable at hand to connect it, so I've plugged the Ground Control to my Triaxis preamp and used its MIDI thru to connect to the GCX; I used a 7 pin midi cable from the Triaxis to the Ground Control plugging Ground Control's wall wart into the auxiliary DC socket on Triaxis' back: that's the last option I have, even though the GC and GCX seem to be communicating the right way...could it be that these issues are due to the GC not being plugged straight in the GCX's "Pedal IN"?

Thanx

JohnClark
Posts: 7401
Joined: Tue May 05, 2009 2:33 pm
Location: The Lab

Re: GCX not passing audio

Post by JohnClark » Fri Nov 11, 2011 6:27 pm

Are you sure this GCX has not been modified in some way? That would be my first assumption as to why it isn't working as expected.

If you connect a guitar directly to a Loop In and run the same loop's Out to the input of your amp, you should be able to run an effect in the Send and Return for a more direct test.
I would doubt that the MIDI routing has anything to do with it since you say that the GCX front panel LEDs are indicating when you turn the loops on or off.


Disregarding the problem for a moment...
gerax wrote:Guitar into front panel "Guitar in">Guitar Out on back panel to Loop In 1>Send to Amp in>FX Send from Amp>GCX Loop 1 Return> GCX Loop 1 out to amp FX Return.
This will in fact allow you to bypass the preamp, but why do you want to do this? Are you ultimately trying to switch between two different preamp sections?
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gerax
Posts: 35
Joined: Thu Jan 27, 2011 10:45 am

Re: GCX not passing audio

Post by gerax » Sat Nov 12, 2011 2:29 am

Yes, it's exactly what I'm trying to do; right now I'm not splitting the signal with an Y cable to run the guitar to both preamps at the same time; I just hooked up the two preamps to two different loops, just to check everything; I did the same with a stompbox, running the output of the first loop to the input of the amp. I get the straight tone of the amp, but no FX from the stomp when the loop is active...

I'll be checking the unit for modifications but the seller didn't mention anything about it.

gerax
Posts: 35
Joined: Thu Jan 27, 2011 10:45 am

Re: GCX not passing audio

Post by gerax » Mon Nov 14, 2011 2:14 am

OK, I sorted it out: it looks strange, but seems like the previous owner had some kind of different programming in the internal GCX chip, as loops 1-4 correspond to switches 5-8 on my Ground Control and 5-8 on GCX correspond to 1-4...
The seller told me about that, but only for the IA capability, not mentioning it extends also to the standard programming. Once I figured this out the behaviour is fine.
I may patch things to the GCX in this reversed order, but it feels a bit awkward...
Is there a way to have this back to standard matching?

JohnClark
Posts: 7401
Joined: Tue May 05, 2009 2:33 pm
Location: The Lab

Re: GCX not passing audio

Post by JohnClark » Thu Nov 17, 2011 11:52 am

I doubt it's in the software... most likely the connectors for the Upper and Lower Relay boards have been swapped. These connections are on the Logic board, directly behind the large processor chip. With the LEDs facing you, the Upper board should be connected to the one on the Right.

Let us know what you find!
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gerax
Posts: 35
Joined: Thu Jan 27, 2011 10:45 am

Re: GCX not passing audio

Post by gerax » Fri Nov 18, 2011 4:47 am

Ok, I'll take a look at it, and provided they are swapped, is it as simple as unplugging and putting them back in the reverse (but standard) order?

Thanx

gerax
Posts: 35
Joined: Thu Jan 27, 2011 10:45 am

Re: GCX not passing audio

Post by gerax » Sat Nov 19, 2011 8:51 am

Just did it! Worked like a charm, now everything is as it should; I'm enjoying my GCX a lot!

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