GCX/Ground control channel switch with Engl Powerball

Q & A for building and interfacing your rack gear with Ground Control Pro and GCX-based systems.
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Trond Norway
Posts: 6
Joined: Wed Apr 26, 2017 1:49 pm

GCX/Ground control channel switch with Engl Powerball

Post by Trond Norway » Wed Apr 26, 2017 2:10 pm

Hi,
I have connected 4 channels, A and B master, bass boost and open/focused functions on my Engl Powerball V1 to loop number
5, 6, 7 and 8 on the GCX using Y cables. So far its working, but i get a ground hum that is not wanted.
I have not done anything regarding latched or momentary configurations.
I would be happy for a little guidance on this :)


Trond

Trond Norway
Posts: 6
Joined: Wed Apr 26, 2017 1:49 pm

Re: GCX/Ground control channel switch with Engl Powerball

Post by Trond Norway » Wed Apr 26, 2017 2:20 pm

I have not yet used any of the 4 first loops, just connected the guitar signal through. When i have the guitar signal straight in
to the amp, theres no hum.

Trond

JohnClark
Posts: 7079
Joined: Tue May 05, 2009 2:33 pm
Location: The Lab

Re: GCX/Ground control channel switch with Engl Powerball

Post by JohnClark » Wed Apr 26, 2017 2:32 pm

Where exactly is the guitar connected when there is hum?

What else is in the rack with the GCX?

Trond Norway
Posts: 6
Joined: Wed Apr 26, 2017 1:49 pm

Re: GCX/Ground control channel switch with Engl Powerball

Post by Trond Norway » Wed Apr 26, 2017 2:38 pm

I tried guitar in in the front and out on loop 1 and also in and out on loop 1. Without any effects connected.
I have not connected anything in the rack yet. I first wanted to get rid of the ground hum.
I plan to use loop 1, 2, 3, and 4 with stomp boxes.

JohnClark
Posts: 7079
Joined: Tue May 05, 2009 2:33 pm
Location: The Lab

Re: GCX/Ground control channel switch with Engl Powerball

Post by JohnClark » Wed Apr 26, 2017 4:30 pm

So only a GCX in a rack and there is a buzz if you pass audio thru the GCX? That is very strange! Is there a power supply or anything with a large transformer above the GCX?

If you connect the guitar to Loop 1 In then run Loop 1 Out to the amp you should be able to hear the guitar even with the GCX powered down. Does that also make noise?

Trond Norway
Posts: 6
Joined: Wed Apr 26, 2017 1:49 pm

Re: GCX/Ground control channel switch with Engl Powerball

Post by Trond Norway » Thu Apr 27, 2017 1:33 am

There is no power supply or transformers in the rack att the moment, just the GCX.
I now tried going through the GCX with power down, and the hum is still there. A tiny bit less though.

Im going to try remove the channel switch cables and then try the effect loop on the amp with one off the loops on the GCX, to see if the hum is there still.

Trond Norway
Posts: 6
Joined: Wed Apr 26, 2017 1:49 pm

Re: GCX/Ground control channel switch with Engl Powerball

Post by Trond Norway » Thu Apr 27, 2017 2:43 am

So now I tried to connect just the effect loop on the Engl to loop nr 4 in the GCX with the same result. It seems like the hum comes whenever i connect the GCX in anyway.
I tested the effect loop on the amp just to make shure, with no connection with the GCX, and it works fine.

JohnClark
Posts: 7079
Joined: Tue May 05, 2009 2:33 pm
Location: The Lab

Re: GCX/Ground control channel switch with Engl Powerball

Post by JohnClark » Thu Apr 27, 2017 9:19 am

OK, so now you have only the amp FX Loop running thru a GCX Loop and still getting the same buzz? Are the connections as follows:
1. Guitar directly to the Amp Instrument Input.
2. Amp FX Send to GCX Loop In.
3. GCX Loop Out to Amp FX Return.

If so, it is difficult to see how this could be a ground loop buzz with no other path for ground... how loud is this noise compared to the guitar level? Have you tried the above setup with a different set of cables just to be certain there isn't one with a failing shield?

Trond Norway
Posts: 6
Joined: Wed Apr 26, 2017 1:49 pm

Re: GCX/Ground control channel switch with Engl Powerball

Post by Trond Norway » Fri Apr 28, 2017 3:51 am

Yes, thats exactly how the chain is.
I will check all cables and also try with another amp this weekend.

Thank you John

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