Problem with US-20 and SY-1000/GM-800

Started by lazerdriver, March 04, 2024, 07:29:37 AM

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lazerdriver

I recently purchased a new US-20 to switch between SY-1000 and GM-800 (via GKC-AD) and have noticed a problem. Depending on which preset the SY-1000 is on, I get a audible pop when I press the A/B switch. The pop is pretty loud and It is worse on louder or high gain SY-1000 presets, subtle on others, and not at all on some. When I get the pop, I can see it register on the SY-1000 in and out meters but not on the GM-800 meters. Also the pop is quite a bit louder when switching from the SY-1000 to the GM-800, regardless of whether I have the SY-1000 connected to the A or B outputs of the US-20.

It seems to be more sensitive to the SY-1000 than the GM-800. For example, if I set the SY-1000 to one of the presets where I don't hear the pop, I can't reproduce the switching pop with any preset on the GM-800. I don't know what that means or if it is relevant. Just an observation.

I have tried cleaning the contacts on all cables and swapping them back and forth between the US-20 outputs. I have both a 2013 Godin LGXT and a guitar with a GK-3, and the problem is the same for both. I searched the forum, but did not find an issue quite like this. There were some posts with links to known issues with the US-20, but I got an error when I clicked on them.

Do I have a defective US-20, or is this a known issue? If it is a known issue, can anything be done to fix it?

Elantric

#1
Could be an Indication of a ground loop.

Id debug by isolation

Run only the following together , nothing else

GK 13 Guitar > US-20
US-20 UNITA OUT > SY-1000
US-20 UNITB OUT > GKC-AD> GM-800

Verify you are using 3 of the official  power supplies, one for each unit 

No other audio connections , no third party power supplies.

* Test for US-20 A/B switching pop anomalies using Headphones connected to SY-1000 Headphone output

* Test for US-20 A/B switching pop anomalies using Headphones connected to GM-800 Headphone output


lazerdriver

Quote from: Elantric on March 04, 2024, 08:27:16 AMCould be an Indication of a ground loop.

Id debug by isolation

Run only the following together , nothing else

GK 13 Guitar > US-20
US-20 UNITA OUT > SY-1000
US-20 UNITB OUT > GKC-AD> GM-800

Verify you are using 3 of the official  power supplies, one for each unit 

No other audio connections , no third party power supplies.

* Test for US-20 A/B switching pop anomalies using Headphones connected to SY-1000 Headphone output

* Test for US-20 A/B switching pop anomalies using Headphones connected to GM-800 Headphone output



I am using the original power supplies for each (SY-1000, GM-800, GKC-AD).

I tested as you suggest: No other cables connected, only power, the GK cables from the US-20, and headphones. Completely silent with headphones connected to the GM-800. Pop with headphones connected to the SY-1000.

Also, I unplugged the SY-1000 from my power strip / surge protector and plugged straight into a wall outlet, and connected the GK cable to the US-20 A output (with nothing connected to the B output). Still get the pop when pressing the A/B switch. Tested this with each of the short GK cables with no difference

gumtown

Check the GKC-AD Guitar Out jack for the 'pop' noise too, "normal guitar" is the only signal not used in the GM-800.

Try a SY-1000 patch which has the normal guitar input disabled.

That could help isolate which part is causing the issue.
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lazerdriver

#4
Quote from: gumtown on March 04, 2024, 12:00:43 PMCheck the GKC-AD Guitar Out jack for the 'pop' noise too, "normal guitar" is the only signal not used in the GM-800.

Try a SY-1000 patch which has the normal guitar input disabled.

That could help isolate which part is causing the issue.

Tried the GKC-AD Guitar Out, plugged it into my amp modeler, with headphones connected to the amp modeler. Silent when switching on the US-20.

It doesn't appear to be related to the normal guitar input of the SY-1000 either. I get the noise on presets that don't have that input enabled and on presets that do.

I ran through the first four banks of SY-1000 factory presets, pretty wide variety of instrument types. The ones marked with asterisk get the loudest click/pop when switching. The others get the noise, but to a lesser degree:

1-1 (dynamic saw lead: dyna x 3)
1-3 (12-string orch: vio, polyfx, ac)
2-3 (advanced gk clean: dyna x 3, normal input)
2-4* (intense filter: dyna, e. gtr, dyna)
3-1* (gr-300 deep rev: gr-300)
3-3 (sitar & pad: dyna, polyfx, ac)
4-3 (eg&ac open g: e.gtr, ac)
4-4* (scarier sequence: dyna x 3)

One of my own presets, a high gain amp via normal input, exhibits the problem too. I guess I can try disabling different effects in the paths of the worst offenders. Not sure what that will tell me in the long run though. If other people have not seen this problem, then it seems I either have a faulty US-20 or something weird going on with the SY-1000.

Elantric

#5
May have to enable the N.S. ( NOISE SUPRESSOR, see SY-1000 Parameter Guide

admin_shawnb

I had never noticed this before, but I am seeing it now, & I recalled this recent thread...

If you have a high gain voice on the SY-1000, and have the SY-1000 plugged into the A port on the US-20, it will pop when you press the US-20 buttons.

For me, the fix was simple: swap the A & B outputs.  I now have the GM-800 plugged into A.  No more pops.

I don't see this as a SY issue so much as a US-20 issue.  The switches aren't quiet enough, & a high gain voice on the A output blows that up.

Elantric

#7
Quote from: admin_shawnb on March 11, 2024, 11:03:11 PMI had never noticed this before, but I am seeing it now, & I recalled this recent thread...

If you have a high gain voice on the SY-1000, and have the SY-1000 plugged into the A port on the US-20, it will pop when you press the US-20 buttons.

For me, the fix was simple: swap the A & B outputs.  I now have the GM-800 plugged into A.  No more pops.

I don't see this as a SY issue so much as a US-20 issue.  The switches aren't quiet enough, & a high gain voice on the A output blows that up.


The US-20 just Grounds the Pin 8 (GK-VOL) GK Volume on the unselected GK Output- Muting the GK Processor

So the SY-1000 "Pop" issue could also manifest if you employ a custom Pin 8 GK Volume implementation on anything ( GK Guitar) or use the GK-3 Three way Guitar /Mix/Synth switch, which also maniplutates Pin 8 GK Volume

Further details of US-20 features /Anomalies

https://www.vguitarforums.com/smf/index.php?topic=2246.0

gumtown

#8
With reference to the US-20 schematic drawing.
A possible solution to help with the switch-over "popping" would be to install two 10uF electrolytic capacitors,
 one from A/B switch pin number 6 to ground,
 the other from A/B switch pin number 2 to ground.
This will slow the voltage rise transient when the switch is opened, giving the effect of the GK-Vol being quickly wound up instead of being suddenly 0 to 100.
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