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GK-13 Reference Knowledge => GK-13 Interface Top things to know => Topic started by: Moonpool on January 28, 2010, 03:16:11 PM

Title: Roland US-20 A/B Selector BUG (Importance of GK-VOL Assignment)
Post by: Moonpool on January 28, 2010, 03:16:11 PM
 (https://i.postimg.cc/76xkXPQX/GK.png)


I use a VG8 primarily and have just purchased a US -20  to integrate my VG99  into my live performing rig.  I tried it out using the preset patches and everything worked fine.  Then, I switched to some patches I downloaded from the site and some I modified from the downloaded patches.  When I was using the downloaded patches some very odd things happened.  For starters, the VG99 would play regardless of what I had the US-20 set to.  The VG 8 did not sound at all. So, after switching between A & B, trying one at a time etc, I also noticed something else odd.  When hooked up to the US 20 with both units properly connected, on those user patches that would only feature the VG99 (even when A&B was selected), it also didn't matter what the volume on my GK3 pickup was set to, the VG99 continued to play, even with the volume turned off completely.

When I went to the unmodified presets, everything worked as expected and scrolling back to the user created patches, the problem arose again.    I'm not fluent enough in working with the signal routing on the 99, but I'm guessing somehow that's at the root of the problem.  I can get more detailed information posted this weekend (I won't have time to hook everything up and test till then), but in the meantime I thought someone may have run into this already.  Obviously, I'd love to use some of the downloaded patches live in conjunction with VG8 patches I use primarily, but I have to have silly workarounds to do that which make it difficult if not impossible to play some things the way I want to when switching between units is involved.

If someone has had this before and it's been discussed, I'd appreciate a link to a step by step solution, otherwise, if you have a solution, I'd love to hear it.  I find the complexity of the programming features a bit daunting, largely because I don't have a lot of time to spend programming, which I know I'll have to do eventually.

Thanks for any help and suggestions,
Frank
Title: Re: Roland US-20 A/B Selector BUG (Importance of GK-VOL Assignment)
Post by: Elantric on January 28, 2010, 05:29:04 PM
Quotethe VG99 continued to play, even with the volume turned off completely.


Review the US-20 Schematics here:

https://www.vguitarforums.com/smf/index.php/topic,480.0.html (https://www.vguitarforums.com/smf/index.php/topic,480.0.html)

Basically  - if GK-3A's onboard 'GK Vol" pot is NOT mapped to Volume Level on the VG-99 - then the US20 will NOT Work!

(https://www.vguitarforums.com/smf/proxy.php?request=http%3A%2F%2Fwww.snapagogo.com%2Fuploads%2Fsource%2F52016%2F1452106663_152346498_schemaus20.jpg&hash=66c0b5b702253b149d2ef2f2417bba0698b73097)

Just know that the Roland GK interface design is flawed.

The GK-3 Three way switch and Roland US-20 A/B/Y Selector  / routers ALL rely on the GK-3 "GK-VOL" pot to be assigned to Patch Volume

If you deviate and get creative, and re-assign GK-VOL to control something other than PATCH VOLUME - that's when bugs manifest.

I always put on suitable background music to sing along when creating Control Assignments  - like

The Clash "Know Your Rights"

but I change the lyrics to suit the operation I'm doing:

"You have the Right to Re-assign the GK-VOL pot,  - as long as you're not Dumb enough to actually try it."
Title: Re: Roland US-20 A/B Selector BUG (Importance of GK-VOL Assignment)
Post by: paults on January 28, 2010, 07:08:56 PM
You'll find that many of the patches you download will have the knob mapped to something other than volume.  If you modify the downloaded patch, your US-20 will function normally.
Title: Re: Roland US-20 A/B Selector BUG (Importance of GK-VOL Assignment)
Post by: big_jan on January 28, 2010, 10:57:28 PM
also check the integrity of the gk cables, i also encounter this issue especially when rushing to setup.
Title: Re: Roland US-20 A/B Selector BUG (Importance of GK-VOL Assignment)
Post by: Moonpool on January 31, 2010, 08:15:57 AM
Okay, I'm still baffled.
The integrity of the cables is fine.  I'm not very good at reading schematics, but the bottom line is that the US20 does indeed function correctly on the Roland created patches on the VG99.  The VG8 patches don't seem to be an issue - I can switch between user created ones and factory presets and it works perfectly.  It's just the odd user created patches in the 99 that cause anomalies.

I scrolled through some of the offending patches that I downloaded, like Flute, Oboe.  When I open the Control assign function on the VG 99 I then open the GK Vol screen  According to that screen (Page 1), Source = GK Vol; SW=ON; Target Parameter reads F4 - {A} COSM GUITAR, F5-E GTR, F6-VOL all from Page One.

Page Two MIN=0, MAX=100; Range LOW =1, Range High=127

Page Three Source=GK VOL, SW=ON, Target Parameter- F4={B} Cosm Guitar, F5= E. Gtr, F6= VOL
Page 4 reads exactly as page three.

I randomly checked another patch, one that worked correctly with US20 (that is, it didn't override the GK VOL control functions and did not override the US 20 select functions, and it was set exactly the same.

To clarify again for those who thought the US 20 didn't work, it did work correctly, but on some patches, only the signal from the VG99 would sound, regardless of whether or not  the selector selected the VG99.  These patches all had on thing in common.  They were downloaded from the site and created by a myriad of different users.

As to the GK VOL screens, there wasn't much consistency.  What I noted before, was that on the patches that did the override, I could turn the GK volume all the way off and still have full signal.  I understand that if the GK Volume control was set to another parameter, say Wave Level, then, that might be the case.  I just don't understand why on some patches, only the VG 99 comes through the US 20 even if I have selected the VG8.

Any other thoughts?  Am I understanding how to assign the GK Vol parameter correctly?

Obviously what I'd like to do is have the VG8 (for example) be set to a main patch for a song and have the VG99 set to another patch I'd switch to and be able to change from A to B on the US 20 to go between them.  If I have one of the user created patches that creates the override issue, I can't do this, as all I get for sound is from the VG99, despite how I have the US 20 set.

Title: Re: Roland US-20 A/B Selector BUG (Importance of GK-VOL Assignment)
Post by: Moonpool on January 31, 2010, 08:43:01 AM
A few further notes.  I just plugged  everything back in for live sound, as opposed to looking it all up on the iMac.  The main offending patches are the Little Wing and Machine Gun patches, the Tin Whistle and the Flute and Oboe, if anyone has downloaded these and is using a US 20 with a VG8, I'd love to hear what happens if you attempt to recreate this situation.

Thanks again.  Oh, and by the way, I really love the patches - when I refer to them as offending  no value judgement is implied.  I simply mean they are the only ones that cause the problem.

Frank
Title: Re: Roland US-20 A/B Selector BUG (Importance of GK-VOL Assignment)
Post by: Brent Flash on January 31, 2010, 09:18:22 AM
Quote from: Moonpool on January 31, 2010, 08:43:01 AM
A few further notes.  I just plugged  everything back in for live sound, as opposed to looking it all up on the iMac.  The main offending patches are the Little Wing and Machine Gun patches, the Tin Whistle and the Flute and Oboe, if anyone has downloaded these and is using a US 20 with a VG8, I'd love to hear what happens if you attempt to recreate this situation.

Thanks again.  Oh, and by the way, I really love the patches - when I refer to them as offending  no value judgement is implied.  I simply mean they are the only ones that cause the problem.

Frank
If you give me an example of one that works, I will look at them to see if I can spot anything. I will compare it to LittleWing.mid
Title: Re: Roland US-20 A/B Selector BUG (Importance of GK-VOL Assignment)
Post by: admin on January 31, 2010, 09:36:32 AM
The Working Factory patches will have the "GK-Vol" assigned to "Patch Level" - Not COSM Guitar Level.

Your Tin Whistle, Flute, Oboe patches will not work with US-20, because they remain having the GK-VOL assigned to COSM Guitar, which is not even used in those patches. Set your  GK-Vol to control Patch Level, and you you should be golden.
Title: Re: Roland US-20 A/B Selector BUG (Importance of GK-VOL Assignment)
Post by: Moonpool on January 31, 2010, 05:29:14 PM
Thanks, I'll try that out first chance I get. Meanwhile for Brent, the two patches I randomly tried that were guitar sounds and worked as expected were 183 (Voxy P90 + strat and 202 Fat LP.  I really appreciate all the assistance and great patches from this site.  I really need more time with this device as it's quite deep and while related. sufficiently different form the VG8 that at times I'm at a total loss wit the programming and tweaking end s of things.
Title: Re: Roland US-20 A/B Selector BUG (Importance of GK-VOL Assignment)
Post by: A2theT on March 23, 2011, 12:12:07 PM
So I have my VG-99 and GR-55 A/B/Y'd using a US-20 which I received a few days ago but have been having a weird thing happening.

VG-99 = Output A
GR-55 = Output B

Basically I'd be playing with Both (Y) units selected and enabled and all ok.  Then I'd play with just the VG-99 (A) and everything works fine.  However, once in a while I'd be using GR-55 (B) only with Both switch unselected yet my VG-99 was outputing sound....?
After tons of troubleshooting I found out that the trouble only occured on certain VG-99 patches.  I found this odd as the logic in my head was telling me that when the US-20 is set to B only there'd be no signal sent to the VG-99.  This is NOT the case.

So now it was time to troubleshoot the patches.

What I've determined is that its strictly related to the GK Volume Knob in the Control Assignment.
If the VG-99 Patch has something other than [A]COSM GTR: E.GTR:VOL assigned to the GK Volume Knob then VG-99 sound will output while you are playing even when the US-20 only has the GR-55 selected.

What I found is that I have a pile of patches where the GK Volume Knob is assigned to "Patch Volume".   Basically all these patches output sound when I play and the US-20 is set to (B)GR-55 only.

I'm not sure if this is a bug or if its by design.  I'm guessing its a limitation of the design regarding how the US-20 handles control messages.

I checked the forum to see if anyone else has been experiencing this issue but found nothing. 

Anyway, its a bit of a pain for me as I've had to make modifications to a lot of patches.

I should also make note that once I fix the patch, I can't seem to break it again.  i.e. a patch was set for GK Volume Knob assigned to Patch Volume, so I change it to COSM Guitar Volume and save and it fixes my problem.  I revert back and reprogram as patch level and everything is still fine.  Really, really weird.


I'd appreciate any comments around this subject.
Title: Re: Roland US-20 A/B Selector BUG (Importance of GK-VOL Assignment)
Post by: Elantric on March 23, 2011, 01:10:28 PM
Review the US-20 GK A/B/Y Selector circuit,
(https://www.vguitarforums.com/smf/proxy.php?request=http%3A%2F%2Fphilwake.free.fr%2Fdivers%2Faf%2Fschema-us-20.jpg&hash=edf4d78f81497af21e56c72475accb814268d06d)




although the US-20 is marketed as an A/B/Y switch box - technically no audio paths are actually switched - instead a Voltage Control (GK-3's  GK-VOL signal) on Pin#8 is employed to effectively "Mute" the undesired connected 13 pin processor (VG-8, VG88, VG-99, GR-55, GR-30, etc)


QuoteWhat I've determined is that its strictly related to the GK Volume Knob in the Control Assignment.
If the VG-99 Patch has something other than [A]COSM GTR: E.GTR:VOL assigned to the GK Volume Knob then VG-99 sound will output while you are playing even when the US-20 only has the GR-55 selected.

It's by design. The production Roland US-20 is full of flaws, since it does not actually switch any audio signals.
https://www.vguitarforums.com/smf/index.php?topic=7423.msg51872#msg51872 (https://www.vguitarforums.com/smf/index.php?topic=7423.msg51872#msg51872)

Also many non Roland 13 pin guitar have problems with GK Volume not being able to fully turn volume off on the connected 13 pin processor ( VG-8,VG-88,VG-99,GR-30,GR-20,GR-33,GR-55) when guitar mounted GK-VOL pot is fully counter-clockwise. More details on this "bug" here:
https://www.vguitarforums.com/smf/index.php?topic=434.msg1567#msg1567 (https://www.vguitarforums.com/smf/index.php?topic=434.msg1567#msg1567)

I would prefer redesigning an improved US-20, using analog switch IC's ( like several Vishay DG-202) - so it actually does switch all the string audio signals and Normal guitar audio signals. 

Here is the stock Roland US-20 - the underlying "A/B", "Both" Foot switch circuits focus on Moving the GK-3's "GK-VOLUME" Control Voltage signal to "0V" (GK13, Pin#8) for the currently non-selected target Roland 13 pin device (GR-55, VG-99, etc)  - effectively making the deselected target device silent (as long as GK Vol is mapped to patch Volume on the connected GK13 processors / Guitar Synth units) . But in practice this method is full of flaws. 



That design decision by Roland might have been fine back in 1996 when the US-20 was designed, but today the Roland US-20 is terribly inadequate for bulk of today's 13 pin gear, where we often have GK-3's "GK-VOL" pot remapped to other non volume related functions.


Manipulating the "A/B" or "Both" foot switches on the US-20 simply re-routes the GK-3 S1 & S2 control lines and the GK-3 Volume control voltage to the target 13 pin processor device selected by the US-20:  Unit A or Unit B or Both.

Observe in the US-20 schematic All 6 string signals (as well as the "normal guitar signal") from the GK-3 are non switched and actually always connected and all GK-3 audio signals are sent to both 13 pin processing units the US20 is feeding. (Unit A & Unit B)

The 20 year old US-20 design relies on the GK-3 Volume control to be assigned to the Master Volume parameter of the connected units (VG-99, GR-55,etc).
When the US-20 "deselects" a connected 13 pin device, it sets the "GK-Vol" control voltage to zero - which essentially "mutes"  the deselected device -therefore: The Roland US-20 A/B box will only work, AS LONG AS you have the GK-3 VOL control set to control Master Volume or PATCH VOLUME (or "GUITAR VOLUME [A&B]") on the connected device! (VG-99,VB-99,GR-55, etc)!!

The problem is in this era of COSM processing, to showcase the new FX parameters for remote GK-3 control, the GK Synth Volume Pot is re-assigned to many other functions / uses besides Volume, (including the factory presets of the recent Roland products) far too many times the US-20 will appear to not be functional and "broken". This is normal.

So the US-20 will not function if you have reassigned the GK-3 Vol control to another parameter, such as Delay level, or EQ control, .

Also note that you MUST connect a 13 pin processor to the US-20's "UNIT A" jack, as this supplies +/-7VDC power to the US-20.


If there were a significant demand, I would redesign the whole US-20 switcher, with actual analog switches on each string signal and market a superior version.

But the truth is there are usually only 50 folks who would want one and only 3 who would actually buy one, and those low numbers dictate the price would have to be large (more than $300) to recoup the production costs. 

Give me an order for 1000 and the price goes way down!
Title: Re: Roland US-20 A/B Selector BUG (Importance of GK-VOL Assignment)
Post by: A2theT on March 24, 2011, 06:16:30 AM
Thanks for this insight Elantric!  Wow, so I've now come to realize that when my GR-55 is selected on B I shouldn't hit "WRITE" on my VG-99 or it will store the patch at volume level zero.  I read through the whole US-20 manual (1 page) and it said nothing of the sort.  This is very important info and should almost be a sticky.  I was set to return the US-20 as defective at one point........

Thanks again for your valuable contribution!
Title: Re: Roland US-20 A/B Selector BUG (Importance of GK-VOL Assignment)
Post by: djidoe on March 24, 2011, 07:22:24 AM
I own a "DIY US-20" made by my brother and I experienced that kind of problem too. Sometimes I have just unit A selected and hearing sounds from unit B. I haven't made any research about the problem but I will surely do.

DjiDoe
Title: Re: Roland US-20 A/B Selector BUG (Importance of GK-VOL Assignment)
Post by: aliensporebomb on March 24, 2011, 07:43:55 AM
Devil's advocate:  Add a second GK3 to the guitar?

Ok, ok, I kid!
Title: Re: Roland US-20 A/B Selector BUG (Importance of GK-VOL Assignment)
Post by: djidoe on April 03, 2011, 05:19:59 PM
Hi, how do your GK-3 switches (S1 & S2) react when your US-20 BOTH switch is engaged ? Is the S1 & S2 switches operate on unit A AND unit B ?

Thanx
Title: Re: Roland US-20 A/B Selector BUG (Importance of GK-VOL Assignment)
Post by: GTRSteven on April 03, 2011, 07:07:53 PM
I used a US-20 with my GR-20 and GR-30 units (see photo from 2009). The way it worked for me is which ever unit was the last one in control (prior to selecting BOTH) is the unit that S1/S2 controlled.
ex. I had GR-20 as Unit A and GR-30 as Unit B. If I was playing Unit B (Piano) and pressed BOTH, Unit A (Sax Section) would sound also and if I used S1/S2 my Piano sound on the GR-30 (Unit B, the last one selected) would change to the next patch.... Hope that's not too confusing... becomes pretty intuitive after a few uses.... GTRSteven

Here's my old set-up, good for a few laughs...
Title: Re: Roland US-20 A/B Selector BUG (Importance of GK-VOL Assignment)
Post by: djidoe on April 05, 2011, 07:23:05 AM
How I understand what you mean, is that "BOTH switch" has nothing to do with S1 & S2 switches. The unit that is selected on the A/B switch is controlled by S1 & S2 switches. Is that what you mean ?
Title: Re: Roland US-20 A/B Selector BUG (Importance of GK-VOL Assignment)
Post by: Whip on May 10, 2011, 08:55:53 PM
Wow! Am I ever glad I bumped into this thread. I thought my US-20 was mental. I had the same thing happen.
Like, the 'B' channel would be single (only one unit sound), but when you clicked 'A', both units would sound. Then when I reversed the hook-up, (swapped 'A' and 'B' 13 pin cables) the reverse happened.... 'A' would be single and 'B' would be both! Mental!
Now that I know about the settings, I will try that tomorrow and see if it works.

Whip
Title: Re: Roland US-20 A/B Selector BUG (Importance of GK-VOL Assignment)
Post by: A2theT on May 11, 2011, 04:58:03 AM
Yes, I had to go and change a lot of my patches and reassign the GK-volume and pick-up selection switches in the VG-99.  When I switched between units with the US-20 or used Both I would have no sound when I should have sound or I'd have both sounding when I should only have one etc...
Title: Re: Roland US-20 A/B Selector BUG (Importance of GK-VOL Assignment)
Post by: Whip on May 13, 2011, 10:38:38 AM
Thanks! Went and changed the setting globally and it works like a charm.
;D ;D ;D 8) 8) 8)

Whip
Title: Re: Roland US-20 A/B Selector BUG (Importance of GK-VOL Assignment)
Post by: mooncaine on May 23, 2011, 08:29:13 PM
Wow, great detective work and troubleshooting. Great to know.
Title: Re: Roland US-20 A/B Selector BUG (Importance of GK-VOL Assignment)
Post by: Bill Ruppert on October 18, 2011, 12:20:37 PM
THANK YOU!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
Title: Re: Roland US-20 A/B Selector BUG (Importance of GK-VOL Assignment)
Post by: 727lawrence on October 18, 2011, 03:53:25 PM
I'm glad I found this thread also. It simply looked to me as though the standard guitar pickup output was being routed to both outputs regardless of the setting. Great thread. Thanks!
Title: Re: Roland US-20 A/B Selector BUG (Importance of GK-VOL Assignment)
Post by: acousticglue on October 19, 2011, 03:39:40 AM
This, to me, is the most difficult thing to wrap myself around. I think we need some step by step how you setup globally the VG99 for use with direct to soundcard output settings or use with pedals and US20. Screenshots show all needed. Any takers?
Title: Re: Roland US-20 A/B Selector BUG (Importance of GK-VOL Assignment)
Post by: shawnb on February 05, 2012, 01:35:50 PM
Folks - I've just run into this myself.   I'd like so share one clarification - mainly to make sure I get it right...   

I also couldn't turn off my VG-99 using the US-20 A/B switch, due to some changes I made a while back.    I had a slightly different issue - I had my System-level GK Vol assign to be GUITAR VOLUME [A&B].   In this config, my Normal PU played thru the US-20's A&B  channels on my voices where I had the Normal PU mixed in.   I.e., the US20 properly handled the COSM guitars, but not my Normal PU.   

So one clarification I would add is this:   If you want:
    (a) control over your cosm guitar volumes (A&B), and
    (b) control over your normal PU volume, and 
    (c) a global solution because you always play your VG-99 thru your US-20

...Then you should change your System-level GK Vol Assign to be either PATCH LEVEL 0-100, PATCH LEVEL 0-200, or MIXER [A&B].   

Avoid the GUITAR VOLUMEs, as this will not provide US-20 control over your Normal PU. 

Feedback & confirmation welcome... 

Shawn
Title: Re: Roland US-20 A/B Selector BUG (Importance of GK-VOL Assignment)
Post by: 80Hz on February 28, 2012, 03:30:54 PM
Quote from:  Elantric on March 23, 2011, 01:10:28 PM
It's by design....
If there were a significant demand, I would redesign the whole US-20 switcher, with actual analog switches on each string signal and market a superior version....
Give me an order for 1000 and the price goes way down!

Elantric, thanks for the detailed information, really cleared things up for me.  Do you work for Roland?   
Here is my WISH list for the next Roland unit (I'll look for an appropriate thread here and re-post it.  Perhaps Roland will take notice.):
Put ALL the VB-99 COSM models and all the GR-55 PCM sounds inside the FC-300 and replace the display with the display from the GR-55.  This would give me everything I need in one floor based unit.  (don't need that ribbon controls...)
I'd be willing to pay as much as $1700 for something like that.
Let me know if you ever need beta testers!
Title: Re: Roland US-20 A/B Selector BUG (Importance of GK-VOL Assignment)
Post by: Elantric on February 28, 2012, 03:59:31 PM
QuoteElantric, thanks for the detailed information, really cleared things up for me.
You are welcome



QuoteDo you work for Roland?

I applied a few times, but its a harsh place to work. My skills are better served in hard core electronic engineering - and Roland has no need for US citizens in that role.

Here's my Bio
https://www.vguitarforums.com/smf/index.php?topic=82.0 (https://www.vguitarforums.com/smf/index.php?topic=82.0)
Title: Re: Roland US-20 A/B Selector BUG (Importance of GK-VOL Assignment)
Post by: cbcbasket on November 26, 2012, 07:19:40 AM
Here is my set up. I am using a new US-20 to switch between a VG-8 and VG-99, but I am getting bleed through from the VG-99 no matter what. And terrible hum on some distortion patches on the VG-99. Ideas? Defective US-20? Ground loop?
Title: Re: Roland US-20 A/B Selector BUG (Importance of GK-VOL Assignment)
Post by: whippinpost91850 on November 26, 2012, 07:25:35 AM
wish the internal kit had a GK3 pickup
Title: Re: Roland US-20 A/B Selector BUG (Importance of GK-VOL Assignment)
Post by: Kevin M on November 26, 2012, 08:48:21 AM
Check your 13 pin cables and try and isolate any ground loop issues by eliminating all but the VG 8 and 99 from the equation. I had some issues with horrible noise in a US 20 that turned out to be a bad 13 pin cable.
Title: Re: Roland US-20 A/B Selector BUG (Importance of GK-VOL Assignment)
Post by: cbcbasket on November 27, 2012, 06:25:39 AM
Thanks, but I did all that already. The hum I can cure someway, but the bleed through I can't seem to stop. I think the US-20 may be defective. I even talked to Roland and that's what they think. I am on hold with Sweetwater even as I type!
Title: Re: Roland US-20 A/B Selector BUG (Importance of GK-VOL Assignment)
Post by: Elantric on November 27, 2012, 10:13:41 AM
What is your 13 pin pickup type?

If its not a Roland, there are known "bleedthrough" volume issues with the US-20, when used with the RMC or Ghost 13 pin pickups
Title: Re: Roland US-20 A/B Selector BUG (Importance of GK-VOL Assignment)
Post by: cbcbasket on November 27, 2012, 10:16:52 AM
My cables are all Roland EXCEPT the VG-99 cable. It's Radio Shack instead of a Rcc2, which someone suggested on here because those are hard to find. Would that matter?
Title: Re: Roland US-20 A/B Selector BUG (Importance of GK-VOL Assignment)
Post by: Elantric on November 27, 2012, 10:19:01 AM
What is your pickup?
(GK-3, Graphtech Ghost, RMC Piezo)?

https://www.vguitarforums.com/smf/index.php?topic=434.msg1906#msg1906 (https://www.vguitarforums.com/smf/index.php?topic=434.msg1906#msg1906)

Further US-20 trouble shooting details are here:
https://www.vguitarforums.com/smf/index.php?topic=3494.msg23360#msg23360 (https://www.vguitarforums.com/smf/index.php?topic=3494.msg23360#msg23360)

Quote
When I purchased my Ghost system in 2004, I noticed that
my volume on my VGs and GRs were VERY low when using a US20, in
comparison to my Godin LGXTs and Multiacs, which used LR Baggs piezo
systems and RMC respectively. As per Lea Rawlings , the main engineer
at Graphtech, I had to have my US20 modified - which was very
inexpensive. Here is his direction to me on March 9, 2004:
"The Roland US20 is a 13-pin switch box that permits connection
of one instrument to two MIDI converters or sound processors. Most
signals pass through the box untouched. The analog signal (pin 7) and
the MIDI volume signal (pin 8  ) are switched and/or muted.
A problem occurs when driving the box with a Hexpander. The box
presenta a low impedance on the MIDI volume pin, which loads down and
reduces the signal produced by the Hexpander. The result is low MIDI
volumes. The loading is due to resistor R13, which is 10K. The actual
value of this resistor is not important - it exists only to pull the
signal to ground when nothing is plugged into the box. Increasing its
value has been found to make the box function properly when driven by
the Hexpander. Increasing the value from 10K to 470K is recommended.
Summary: In the US20 box, on the main printed circuit board, locate
R13 (a 10K resistor), remove it, and replace it with a miniature 470K
resistor( e.g. Digi-Key part number 470KE)."
I think the resistor cost about $25.00, but I am not sure
about that. After this change was made, the Ghost sytem volume was
fine !! Again, NO modification is needed with either the LR Baggs, or
the RMC systems using a US20 - only the Graphtech system. That was
nearly 3 yrs. ago, and maybe Graphtec has addressed this issue.
Mark


QuoteThe US-20 differs from the rest of the DIN-13 products in that the Synth
Volume line (line #8) is usually pulled up to +5VDC using a 47K ohm resistor.
Unfortunately, in the US-20, there is a 10K ohm resistor to Ground. The pre
2000 Brian Moores with RMC did not have a synth volume buffer and this
was initially causing a problem with the US-20 where the maximum synth volume
voltage could not be achieved.

The mod is simply to remove the 10K resistor (R13) and add a 68K resistor
between
pin 5 and pin 8 of IC 1.

Many of the pre-2000 Brian Moores were retro-fitted with synth volume buffers
at the factory, and since 2000, all Poly-Drive 1 preamps have a built-in synth
volume buffer, so this is immaterial in the newer instruments.

I believe this topic was already discussed some years ago.

Hope this clarifies that issue.

Best regards,

RMC
Title: Re: Roland US-20 A/B Selector BUG (Importance of GK-VOL Assignment)
Post by: cbcbasket on November 27, 2012, 10:20:39 AM
GK2 on a standard Strat. I have a PRS with Ghost but haven't tried it yet.
Title: Re: Roland US-20 A/B Selector BUG (Importance of GK-VOL Assignment)
Post by: concordal on March 05, 2013, 11:12:08 AM
Yes , it's another US-20 mystery today.

As explained earlier in this thread, the US-20 switch will function correctly only if the GK Vol ASSIGNment is set to control Master Volume on the connected devices -  in my situation, the GR-55 and the VG-99.  This setting can be done either globally or per patch.

I control patch volume from either GK Vol  OR  the EXP Pedal 1 on the FC-300.  This actually works quite well and the two controls don't fight each other. 

But enter the US-20.  With both GK Vol  AND the EXP pedal set to control patch volume here's what happens:  When the US-20 is switched to the "A" side, the GK Vol control works nicely.  But if I touch the EXP Pedal, the "B" side bleeds through.  Aaargh.

1.  Is there any way around this? 

2.  Would the SGUS-3 switch (from http://www.chd-el.cz/index.php?id=140&lngid=en (http://www.chd-el.cz/index.php?id=140&lngid=en)) be of any help?  i.e. does the SGUS-3 work on a different principle?

Any suggestions appreciated.
Title: Re: Roland US-20 A/B Selector BUG (Importance of GK-VOL Assignment)
Post by: Elantric on March 05, 2013, 11:32:39 AM
Last i heard, the developer of the S-GUS 3 in Czechoslovakia is no longer making these.

The production Roland US-20 is full of flaws, since it does not actually switch any audio signals, look at schematic below and see the only thing that is switching is the GK Vol control signal on Pin#8
It relies on the GK VOLUME assignment on the GK 13 processors that are connected
(VG-99, VB-99, GR-20, GR-33, GR-55 Must have GK VOLUME assignment set to PATCH VOLUME)
https://www.vguitarforums.com/smf/index.php?topic=7423.msg51872#msg51872 (https://www.vguitarforums.com/smf/index.php?topic=7423.msg51872#msg51872)

I would prefer one that does, using analog switches like several Vishay DG-202 

Here is the stock Roland US-20 - the switch elements focus on Moving the "GK-Vol" Control Voltage to "0V" for the unused target 13 pin device (GR-55, VG-99, etc)
(https://www.vguitarforums.com/smf/proxy.php?request=http%3A%2F%2Fphilwake.free.fr%2Fdivers%2Fdocs%2Fus-20%2Fschematic%2520us-20.jpg&hash=44c6c909eef11f413e1c9679a9e51721cafd8aa5)


That design decision by Roland might have been fine back in 1996 when the US-20 was designed, but today the Roland US-20 is terribly inadequate for bulk of today's 13 pin gear, where we often have "GK-VOL" remapped to other non volume related functions.

I know several members here on VGuitarForums who over the past 4 years are working on an "Improved US-20"  - its really time we all address this and create one asap.


http://launch.dir.groups.yahoo.com/group/vg-8/message/11597 (http://launch.dir.groups.yahoo.com/group/vg-8/message/11597)

http://pekveren.home.xs4all.nl/us20/ (http://pekveren.home.xs4all.nl/us20/)

http://www.muc.de/~hm/music/us-20/ (http://www.muc.de/~hm/music/us-20/)

https://www.vguitarforums.com/smf/index.php?topic=3994.25 (https://www.vguitarforums.com/smf/index.php?topic=3994.25)

(https://www.vguitarforums.com/smf/proxy.php?request=http%3A%2F%2Fwww.whyleuwait.com%2FGR%2FUS20.jpg&hash=d40f1868b895841553e5b3f715a7855f4e2e4a40)
Title: Re: Roland US-20 A/B Selector BUG (Importance of GK-VOL Assignment)
Post by: concordal on March 06, 2013, 10:45:01 AM
Thanks, Elantric. 

In the meantime, any suggestions for a "work-around" from anyone with similar experience would be much appreciated.

Title: Re: Roland US-20 A/B Selector BUG (Importance of GK-VOL Assignment)
Post by: Elantric on March 06, 2013, 10:52:56 AM
Some use a VGA Switch box, to switch all signals with homebrew HD15 to DIN13 adapters.

https://www.vguitarforums.com/smf/index.php?topic=3762.msg25559#msg25559 (https://www.vguitarforums.com/smf/index.php?topic=3762.msg25559#msg25559)
Title: Re: Roland US-20 A/B Selector BUG (Importance of GK-VOL Assignment)
Post by: jshortz on December 30, 2013, 12:09:14 PM
I tried everything on this thread including watching the videos and I still cant get my US-20 to cooperate with my 55 and GR-20.
Set the GK volume correctly I think.
I do use the Exp to control volumes and other things on all of my patches.I wonder if that could be the issue.
If there is a step by step method for the correct setup in my 55 I would really appreciate if someone could post it.
Im playing a RR Strat by the way.
Happy New Year all.
Title: Re: Roland US-20 A/B Selector BUG (Importance of GK-VOL Assignment)
Post by: Elantric on December 30, 2013, 12:16:28 PM
The important thing is "What is your GK-3  Volume (GK-VOL)  set to on GR-20 and GR-55?

None of the factory patches on GR-55 will work with US-20  - you must go through every GR-55 USER patch  -
and assign GK VOLUME  = PATCH VOLUME

as seen here on far right:
(https://www.vguitarforums.com/smf/proxy.php?request=http%3A%2F%2Fwww.snapagogo.com%2Fuploads%2Fsource%2F3632013%2F1388434555_263527206_GR55_GK_VOL.PNG&hash=a0686b8da2c02d6122789c2241a3eee291300f74)


then on GR-20  - you must do the same thing, assign GK VOLUME  = PATCH VOLUME.

Then the US-20 A/B/Both selector should work.
Title: Re: Roland US-20 A/B Selector BUG (Importance of GK-VOL Assignment)
Post by: jshortz on December 30, 2013, 01:09:56 PM
Im not sure if this is possible.
GK VOLUME  = PATCH VOLUME on GR-20.
Title: Re: Roland US-20 A/B Selector BUG (Importance of GK-VOL Assignment)
Post by: Elantric on December 30, 2013, 01:22:01 PM
If you simply plug your 13pin guitar into the GR20, what does the GK-3 Volume knob do?
Title: Re: Roland US-20 A/B Selector BUG (Importance of GK-VOL Assignment)
Post by: jshortz on December 31, 2013, 06:29:43 AM
I will let you know.
Title: Re: Roland US-20 A/B Selector BUG (Importance of GK-VOL Assignment)
Post by: jshortz on January 02, 2014, 12:53:20 PM
The GK Volume controls the synth tone of the GR-20.
Not the guitar volume.
The Exp pedal on the GR-20 also controls only the synth volume and not the guitar volume.
I think my 3 way switch is an issue here.
I did set the GK Volume to patch volume on the 55 like the screenshot you posted.
Still having an issue with both units working.
I only get sound from the unit that is plugged in the amp.
Im supposed to get both with only one plugged in the amp correct?
Title: Re: Roland US-20 A/B Selector BUG (Importance of GK-VOL Assignment)
Post by: Elantric on January 02, 2014, 01:08:16 PM
QuoteThe GK Volume controls the synth tone of the GR-20.

There are no guitar tones in the GR-20 - so when you say "GK Volume controls the synth tone" - I assume this is controlling GR-20 Synth Volume?


Read the GR-20 Owners manual if you are confused.
http://media.rolandus.com/manuals/GR-20GK_OM.pdf (http://media.rolandus.com/manuals/GR-20GK_OM.pdf)

and
Read the US-20 Owners manual.
http://media.rolandus.com/manuals/US-20_OM.pdf (http://media.rolandus.com/manuals/US-20_OM.pdf)

The US-20 A/B Selector switches the GK 13 pin INPUT Audio Connection to two separate GK 13 pin processors (Unit A and Unit B)

Meanwhile the Audio OUTPUTS of all connected 13 pin processors (Unit A and Unit B) (GR-55 AND GR-20 in your case) Must have their associated Audio Outputs connected to feed a separate audio mixer or amplifier with multiple inputs  - like a Keyboard amp, or Roland CM-30
QuoteI only get sound from the unit that is plugged in the amp
Should be obvious, but you will need to connect BOTH GR-55 AND GR-20 Outputs to an Amp, or PA, or Mixer , the US-20 will simply mute the input to the non-selected GK13 device.
Title: Re: Roland US-20 A/B Selector BUG (Importance of GK-VOL Assignment)
Post by: jshortz on January 02, 2014, 01:20:53 PM
Excellent.
That's my next move.
Let you know the result.
Thanks
Title: Re: Roland US-20 A/B Selector BUG (Importance of GK-VOL Assignment)
Post by: jshortz on January 03, 2014, 01:18:16 PM
Success....
Using my A/B/Y box I got the GR-20 and 55 to switch like they should.
The only issue is that the only way to defeat the Normal pickups from the GR-20(the normal pickups stay on toe up and the synth comes in toe down along with the normal pickups) is to put the 3 way switch to synth only.
That restricts the use of the normal pickups for the 55 and a modeled guitar is the only choice.
I cant think of a way around that but I am glad the US-20 functions as it should.I hope I explained this correctly.
Thanks for the help.
Title: Re: Roland US-20 A/B Selector BUG (Importance of GK-VOL Assignment)
Post by: Elantric on January 03, 2014, 01:25:20 PM
Quotethe only way to defeat the Normal pickups from the GR-20(the normal pickups stay on toe up and the synth comes in toe down along with the normal pickups)

I assume this is the GR-20's Expression pedal?

I suppose you could work the GR-20's Expression pedal along with using the US-20's A/B, Both foot switches, or simply remove the Normal Guitar feed signal to the GR-20  - easiest way to do that is modify the short 13 pin cable feeding the GR-20, by clipping the pin #7 wire inside the cable. 
Title: Re: Roland US-20 A/B Selector BUG (Importance of GK-VOL Assignment)
Post by: jshortz on January 03, 2014, 01:43:31 PM
Yes it is the GR-20's Expression pedal.
Title: Re: Roland US-20 A/B Selector BUG (Importance of GK-VOL Assignment)
Post by: Elantric on March 23, 2014, 02:15:13 PM
QuoteI've been getting an intermittent "mains" type hum from the vg99. In the high gain patches, it's nearly as loud as the actual guitar signal.
I don't use my mags, only the internal GK, I have a US20 feeding the 99 and a GR55, but I tried plugging the GK lead directly into the 99, without curing the problem. The GK lead is almost new.
Has anyone else had this happen, or have any ideas please?
Hopeful regards,

Yes  - its the typical  US-20 Ground loop.

Solved by using an Ebtech  Hum-X on the Roland AC power brick supply to either the GR-55 or VG-99 - only need one.

http://www.amazon.com/Ebtech-Hum-Voltage-Filter/dp/B0002E4YI8/ref=sr_1_1?ie=UTF8&qid=1395607736&sr=8-1&keywords=Ebtech+Hum-X (http://www.amazon.com/Ebtech-Hum-Voltage-Filter/dp/B0002E4YI8/ref=sr_1_1?ie=UTF8&qid=1395607736&sr=8-1&keywords=Ebtech+Hum-X)

(https://www.vguitarforums.com/smf/proxy.php?request=http%3A%2F%2Fwww.ebtechaudio.com%2Fhumxsplashbanner.jpg&hash=40ff4758b683481b588ce8145e56a07a65b73044)

Title: Re: Roland US-20 A/B Selector BUG (Importance of GK-VOL Assignment)
Post by: VGrider on May 07, 2014, 01:13:22 PM
The US-20 is too expensive!!  $220 for an A/B switch?
Could I make a ~passive one with a couple Analog Switches like the ADG1434 linked here:  http://www.analog.com/en/switchesmultiplexers/analog-switches/adg1434/products/product.html (http://www.analog.com/en/switchesmultiplexers/analog-switches/adg1434/products/product.html)

Title: Re: Roland US-20 A/B Selector BUG (Importance of GK-VOL Assignment)
Post by: Elantric on May 07, 2014, 01:16:59 PM
Realize the Roland US-20 price includes two 1 meter 13 pin cables which accounts for $80 of the price of the Roland US-20.


DIY US-20 plans are here:
https://www.vguitarforums.com/smf/index.php?topic=480.0 (https://www.vguitarforums.com/smf/index.php?topic=480.0)
Title: Re: Roland US-20 A/B Selector BUG (Importance of GK-VOL Assignment)
Post by: datsunrobbie on May 08, 2014, 02:02:35 PM
Check eBay frequently, decide what it's worth and keep bidding. I picked mine up for around $100, but I had to bid on half a dozen auctions before I finally got one at that price. I just checked their completed listings for us-20 and the lowest price I saw was a $100 on a "buy it now" listing.
Title: Re: Roland US-20 A/B Selector BUG (Importance of GK-VOL Assignment)
Post by: jshortz on January 02, 2015, 09:50:27 AM
I set up my US-20 with GR-55 and GR-20 and for some reason both units stayed on when only one was selected.
Odd thing as it only happens on occasion.
My cables are clean.
Title: Re: Roland US-20 A/B Selector BUG (Importance of GK-VOL Assignment)
Post by: Elantric on January 02, 2015, 10:10:52 AM
Both units must have "GK Vol" assigned to patch volume for the US-20 to operate
Title: Re: Roland US-20 A/B Selector BUG (Importance of GK-VOL Assignment)
Post by: Deus02 on January 31, 2015, 10:43:15 AM
Quote from:  Elantric on January 02, 2015, 10:10:52 AM
Both units must have "GK Vol" assigned to patch volume for the US-20 to operate

Just wondering if a switching unit exists that actually does the opposite of the US-20?  (I. E.  "2" - 13 pin ins, ONE out). 
Title: Re: Roland US-20 A/B Selector BUG (Importance of GK-VOL Assignment)
Post by: Elantric on January 31, 2015, 01:24:01 PM
Read the GK Accessory Area for these type products
https://www.vguitarforums.com/smf/index.php?board=13.0 (https://www.vguitarforums.com/smf/index.php?board=13.0)

There used to be the Czech CHD version
http://www.chd-el.cz/index.php?id=4#id17 (http://www.chd-el.cz/index.php?id=4#id17)


And today a few ares listed here:

https://www.vguitarforums.com/smf/index.php?board=174.0 (https://www.vguitarforums.com/smf/index.php?board=174.0)


there is the PrimANova version from CodeSmart
Quote4 guitars in (GK or std. 1/4 jack), effect loop, on board S1 & S2 switches in case you connect something without S1/S2 buttons.
12VDC power possibility in case your instruments consumes more than 200mA.

Guitar, Chapman stick, GK-violin - These yellow guys built like tanks switches Everything.

1 meter great quality gold plated GK Cable included.

Todays price including shipping:
United states: 298 USD
All Europe:     267 Euro (25% VAT included)
Australia:       333 AUD

https://www.vguitarforums.com/smf/index.php?topic=9143.0 (https://www.vguitarforums.com/smf/index.php?topic=9143.0)
(https://www.primovasound.com/gfx/gkmx41_7.jpg)


DrJoness has his here
https://www.vguitarforums.com/smf/index.php?topic=9346.0 (https://www.vguitarforums.com/smf/index.php?topic=9346.0)

(https://www.vguitarforums.com/smf/index.php?action=dlattach;topic=9346.0;attach=7856;image)
Title: Re: Roland US-20 A/B Selector BUG (Importance of GK-VOL Assignment)
Post by: zapantalambda on February 06, 2015, 07:45:07 PM
***Hello Guitar gurus & Sonic enthusiasts***

I got a question to ask
Probably a longshot but I'm just testing the waters to see if there's anyone in here who's willing to part out with their modded Roland US20?
I dont really mind if it has cosmetic wear. What i'm after is a functional unit in good working condition.
The reason being is, Im experimenting on my set-up right now and I just need the modded US20 as piece in the puzzle.
If anyone wants to let go of their unit, would yous pls let me know. thanks very much
I appreciate your help. Rgds -zap
Title: Re: Roland US-20 A/B Selector BUG (Importance of GK-VOL Assignment)
Post by: Silas Lang on June 17, 2015, 01:50:36 AM
More US-20 oddity: I use it with a GR-55 and a VG-99, both with GK volume assigned to "patch volume" as stated by Elantric. It works ok until I change to a different patch (both units at the same time via midi); then, the VG-99 always sounds even if only the GR-55 is selected. If I switch on and off the pedal marked "Both". the VG-99 mutes again. It only happens with the VG-99, no problem with the GR-55 whatsoever. I don't have a clue how to solve this, anyone?

Forgot to mention: of course the assign of GK volume is "global", not "per patch".
Title: Re: Roland US-20 A/B Selector BUG (Importance of GK-VOL Assignment)
Post by: shawnb on June 17, 2015, 11:17:58 AM
That sounds familiar...  IIRC, it's 'patch level' or 'guitar volume', not 'patch volume'?  So you might want to double-check. 

Note this post from earlier in this thread:
https://www.vguitarforums.com/smf/index.php?topic=2246.msg36222#msg36222 (https://www.vguitarforums.com/smf/index.php?topic=2246.msg36222#msg36222)

I also couldn't turn off my VG-99 using the US-20 A/B switch, due to some changes I made a while back.    I had a slightly different issue - I had my System-level GK Vol assign to be GUITAR VOLUME [A&B].   In this config, my Normal PU played thru the US-20's A&B  channels on my voices where I had the Normal PU mixed in.   I.e., the US20 properly handled the COSM guitars, but not my Normal PU.   

So one clarification I would add is this:   If you want:
    (a) control over your cosm guitar volumes (A&B), and
    (b) control over your normal PU volume, and 
    (c) a global solution because you always play your VG-99 thru your US-20

...Then you should change your System-level GK Vol Assign to be either PATCH LEVEL 0-100, PATCH LEVEL 0-200, or MIXER [A&B].   

Avoid the GUITAR VOLUMEs, as this will not provide US-20 control over your Normal PU. 
Title: Re: Roland US-20 A/B Selector BUG (Importance of GK-VOL Assignment)
Post by: Silas Lang on June 22, 2015, 02:21:10 AM
Thanks for the reply, Shawnb. Yes, you're right, the actual mode selected is "patch volume 0-100". And for the "guitar volume" thing, I've never used that way, so it doesn't apply to my situation.

I've assigned gk volume to patch level and mixer without success. Maybe I have to cast a spell on the device to solve the problem!
Title: Re: Roland US-20 A/B Selector BUG (Importance of GK-VOL Assignment)
Post by: rowka on February 01, 2018, 05:32:22 PM
My US-20 GR-55 problem:

I've got the US-20 connected to a VB-99 and GR-55.  Both units have the GK-VOL set to (V-Bass Level) and (Patch Volume).
GK-S1 and GK-S2 work as expected on both units.
The VB-99 behaves as expected.
The GR-55 ONLY sounds when BOTH is selected on the US-20.  Regardless of whether it's hooked up to A or B on the US-20.
Additionally, when BOTH is off and I switch the A/B to the GR-55 it sounds for the briefest moment before going quiet.  Again, regardless of whether it's hooked up to A or B on the US-20.

Thoughts?
Title: Re: Roland US-20 A/B Selector BUG (Importance of GK-VOL Assignment)
Post by: admin on February 01, 2018, 06:03:11 PM
Quote from: rowka on February 01, 2018, 05:32:22 PM
My US-20 GR-55 problem:

I've got the US-20 connected to a VB-99 and GR-55.  Both units have the GK-VOL set to (V-Bass Level) and (Patch Volume).
GK-S1 and GK-S2 work as expected on both units.
The VB-99 behaves as expected.
The GR-55 ONLY sounds when BOTH is selected on the US-20.  Regardless of whether it's hooked up to A or B on the US-20.
Additionally, when BOTH is off and I switch the A/B to the GR-55 it sounds for the briefest moment before going quiet.  Again, regardless of whether it's hooked up to A or B on the US-20.

Thoughts?

check "Assign Hold" setting on GR-55
Title: Re: Roland US-20 A/B Selector BUG (Importance of GK-VOL Assignment)
Post by: rowka on February 01, 2018, 06:23:30 PM
"Assign Hold" setting is not making any difference.
Title: Re: Roland US-20 A/B Selector BUG (Importance of GK-VOL Assignment)
Post by: rowka on February 03, 2018, 10:24:54 AM
I can totally work around it, but it seems odd.

Unless, I'm just not finding the correct "Assign Hold" on the GR-55.  The only place I found it is under General Midi, which seems an odd place for it.