Author Topic: Roland US-20 A/B Selector BUG (Importance of GK-VOL Assignment)  (Read 9542 times)

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Offline 80Hz

Re: Roland US-20 A/B Selector BUG (Importance of GK-VOL Assignment)
« Reply #25 on: February 28, 2012, 05:30:54 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!
« Last Edit: November 07, 2013, 04:54:20 AM by Elantric »

Offline Elantric

Re: Roland US-20 A/B Selector BUG (Importance of GK-VOL Assignment)
« Reply #26 on: February 28, 2012, 05:59:31 PM »
Quote
Elantric, thanks for the detailed information, really cleared things up for me.
You are welcome



Quote
Do 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
http://www.vguitarforums.com/smf/index.php?topic=82.0
« Last Edit: November 07, 2013, 04:54:02 AM by Elantric »

Offline cbcbasket

Re: Roland US-20 A/B Selector BUG (Importance of GK-VOL Assignment)
« Reply #27 on: November 26, 2012, 09:19:40 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?
« Last Edit: January 12, 2014, 03:00:02 AM by Elantric »

Offline whippinpost91850

Re: Roland US-20 A/B Selector BUG (Importance of GK-VOL Assignment)
« Reply #28 on: November 26, 2012, 09:25:35 AM »
wish the internal kit had a GK3 pickup

Offline Kevin M

Re: Roland US-20 A/B Selector BUG (Importance of GK-VOL Assignment)
« Reply #29 on: November 26, 2012, 10:48:21 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.

Offline cbcbasket

Re: Roland US-20 A/B Selector BUG (Importance of GK-VOL Assignment)
« Reply #30 on: November 27, 2012, 08:25:39 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!

Offline Elantric

Re: Roland US-20 A/B Selector BUG (Importance of GK-VOL Assignment)
« Reply #31 on: November 27, 2012, 12:13:41 PM »
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

Offline cbcbasket

Re: Roland US-20 A/B Selector BUG (Importance of GK-VOL Assignment)
« Reply #32 on: November 27, 2012, 12:16:52 PM »
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?

Offline Elantric

Re: Roland US-20 A/B Selector BUG (Importance of GK-VOL Assignment)
« Reply #33 on: November 27, 2012, 12:19:01 PM »
What is your pickup?
(GK-3, Graphtech Ghost, RMC Piezo)?

http://www.vguitarforums.com/smf/index.php?topic=434.msg1906#msg1906

Further US-20 trouble shooting details are here:
http://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


Quote
The 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
« Last Edit: January 12, 2014, 03:01:22 AM by Elantric »

Offline cbcbasket

Re: Roland US-20 A/B Selector BUG (Importance of GK-VOL Assignment)
« Reply #34 on: November 27, 2012, 12:20:39 PM »
GK2 on a standard Strat. I have a PRS with Ghost but haven't tried it yet.

Offline concordal

Re: Roland US-20 A/B Selector BUG (Importance of GK-VOL Assignment)
« Reply #35 on: March 05, 2013, 01:12:08 PM »
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) be of any help?  i.e. does the SGUS-3 work on a different principle?

Any suggestions appreciated.
« Last Edit: November 07, 2013, 04:53:45 AM by Elantric »

Offline Elantric

Re: Roland US-20 A/B Selector BUG (Importance of GK-VOL Assignment)
« Reply #36 on: March 05, 2013, 01:32:39 PM »
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)
http://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)



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://pekveren.home.xs4all.nl/us20/

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

http://www.vguitarforums.com/smf/index.php?topic=3994.25

« Last Edit: December 30, 2013, 02:24:52 PM by Elantric »

Offline concordal

Re: Roland US-20 A/B Selector BUG (Importance of GK-VOL Assignment)
« Reply #37 on: March 06, 2013, 12:45:01 PM »
Thanks, Elantric. 

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

« Last Edit: November 07, 2013, 04:53:08 AM by Elantric »

Offline Elantric

Re: Roland US-20 A/B Selector BUG (Importance of GK-VOL Assignment)
« Reply #38 on: March 06, 2013, 12:52:56 PM »
Some use a VGA Switch box, to switch all signals with homebrew HD15 to DIN13 adapters.

http://www.vguitarforums.com/smf/index.php?topic=3762.msg25559#msg25559
« Last Edit: November 07, 2013, 04:52:52 AM by Elantric »

Offline jshortz

Re: Roland US-20 A/B Selector BUG (Importance of GK-VOL Assignment)
« Reply #39 on: December 30, 2013, 02:09:14 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.

Offline Elantric

Re: Roland US-20 A/B Selector BUG (Importance of GK-VOL Assignment)
« Reply #40 on: December 30, 2013, 02:16:28 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:



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.
« Last Edit: December 30, 2013, 02:26:59 PM by Elantric »

Offline jshortz

Re: Roland US-20 A/B Selector BUG (Importance of GK-VOL Assignment)
« Reply #41 on: December 30, 2013, 03:09:56 PM »
Im not sure if this is possible.
GK VOLUME  = PATCH VOLUME on GR-20.

Offline Elantric

Re: Roland US-20 A/B Selector BUG (Importance of GK-VOL Assignment)
« Reply #42 on: December 30, 2013, 03:22:01 PM »
If you simply plug your 13pin guitar into the GR20, what does the GK-3 Volume knob do?

Offline jshortz

Re: Roland US-20 A/B Selector BUG (Importance of GK-VOL Assignment)
« Reply #43 on: December 31, 2013, 08:29:43 AM »
I will let you know.

Offline jshortz

Re: Roland US-20 A/B Selector BUG (Importance of GK-VOL Assignment)
« Reply #44 on: January 02, 2014, 02:53:20 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?

Offline Elantric

Re: Roland US-20 A/B Selector BUG (Importance of GK-VOL Assignment)
« Reply #45 on: January 02, 2014, 03:08:16 PM »
Quote
The 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

and
Read the US-20 Owners manual.
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
Quote
I 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.
« Last Edit: January 03, 2014, 07:30:46 PM by Elantric »

Offline jshortz

Re: Roland US-20 A/B Selector BUG (Importance of GK-VOL Assignment)
« Reply #46 on: January 02, 2014, 03:20:53 PM »
Excellent.
That's my next move.
Let you know the result.
Thanks

Offline jshortz

Re: Roland US-20 A/B Selector BUG (Importance of GK-VOL Assignment)
« Reply #47 on: January 03, 2014, 03:18:16 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.

Offline Elantric

Re: Roland US-20 A/B Selector BUG (Importance of GK-VOL Assignment)
« Reply #48 on: January 03, 2014, 03:25:20 PM »
Quote
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)

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. 

Offline jshortz

Re: Roland US-20 A/B Selector BUG (Importance of GK-VOL Assignment)
« Reply #49 on: January 03, 2014, 03:43:31 PM »
Yes it is the GR-20's Expression pedal.