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GK-13 Reference Knowledge => GK Piezo Hex (RMC,Ghost,etc) => Topic started by: ztones on February 28, 2008, 01:53:26 PM

Title: GODIN-Volume bleed through even with knob turned to zero (US-20 problem)
Post by: ztones on February 28, 2008, 01:53:26 PM
On certain patches I can't turn the volume completely off.  I turn the knob on my Godin LGXT and the regual pickup volume all the way down and still hear some sound.  On patches where there is NO regular pickup volume (it is set to zero in the patch), I switch my GK swith to be regular pickup only and I am still hearing some of the sound, although its at a lower volume.  Is anyone else getting this volume bleed through?  No matter what I do, turn all my volume knobs to zero and still there is some sound....
Title: Re: Volume bleed through even with knob turned to zero
Post by: jon_bondy on February 28, 2008, 01:58:40 PM
Are these your patches, or patches from the standard VG setup?  If the latter, could you name/number them?  If the former, can you provide some of the patches for the rest of us to play with?

:)

Jon
Title: Re: Volume bleed through even with knob turned to zero
Post by: ztones on February 28, 2008, 07:31:43 PM
Since I only use patches that I have edited one way or another, I can't really say if it did it before I edited it and it was just a factory setting.  However, what I have noticed is when I am looking at the editor's virtual guitar and I am turning my Gk volume up and down, it stops at 2.  In other words, it does not go to zero.  If I click it with the mouse, I can make it go to zero and the sound stops completely.  Howerver, when i turn the knob again on the guitar, it does not go to zero, just stops at 2 and that's it.  Seems like some sort of calibration of the volume knob??? Actually I've been saying GK3, but its a GODIN LGXT with a built in LR Baggs type Piezo...but its the same for intensive purposes.  Thanks!
Title: Re: Volume bleed through even with knob turned to zero
Post by: vanceg on February 29, 2008, 04:03:12 PM
It sure sounds (for all intents and purposes) like you have a calibration issue with that volume knob.  I do not know of any way inside the VG-99 to calibrate this.

Vance


Quote from: ztones on February 28, 2008, 07:31:43 PM
Since I only use patches that I have edited one way or another, I can't really say if it did it before I edited it and it was just a factory setting.  However, what I have noticed is when I am looking at the editor's virtual guitar and I am turning my Gk volume up and down, it stops at 2.  In other words, it does not go to zero.  If I click it with the mouse, I can make it go to zero and the sound stops completely.  Howerver, when i turn the knob again on the guitar, it does not go to zero, just stops at 2 and that's it.  Seems like some sort of calibration of the volume knob??? Actually I've been saying GK3, but its a GODIN LGXT with a built in LR Baggs type Piezo...but its the same for intensive purposes.  Thanks!
Title: Re: Volume bleed through even with knob turned to zero
Post by: Elantric on February 29, 2008, 04:14:10 PM
Or a defective solder connection on the internal GK Volume pot

Or a bad 13 pin cable
Title: Re: Volume bleed through even with knob turned to zero
Post by: ztones on March 05, 2008, 08:03:03 PM
I have a few cables and the problem persists with all of them.  The cable is new by the way.  The volume knob problem is with a GODIN LGXT, which is not a cheap built in 13 pin setup.  Could the string sensitivity have something to do with it?
Title: Re: Volume bleed through even with knob turned to zero
Post by: ztones on March 07, 2008, 09:10:48 AM
 ??? ANYONE? BUELLER?  OK..NOT EVERYONE GOT THAT ... SERIOUSLY, ANYONE ELSE WITH VOLUME NOT GOING DOWN TO 0 THAT FOUND A SOLUTION TO THIS?  THANKS!
Title: Re: Volume bleed through even with knob turned to zero
Post by: Elantric on March 07, 2008, 09:37:47 AM
The problem is that many VG-99 patches have the GK Vol Knob mapped to a Tone control function - Not Volume control.

Load the problem patch in the VG-99 Editor and look at what function the GK-Vol Knob is mapped to.
Title: Re: Volume bleed through even with knob turned to zero
Post by: ztones on March 07, 2008, 09:53:57 AM
It is defenitely adjusting the volume so it is mapped to the volume function.  As I turn the volume knob on the guitar, I can see the numbers go from 100 down to 2 in the editor, but it doesn't go to 0.  Stops at 2.  I have to click on it with the mouse to turn it to zero and then its fine.  But when I do it with the guitar, it only goes down to 2.
Like I said, I have tried other cables and this is a high end nice built in 13 system in my Godin LGXT so I doubt its the wiring or soldering.... or could it be?
Title: Re: Volume bleed through even with knob turned to zero
Post by: ztones on March 07, 2008, 12:03:17 PM
I just figured it out. The source of the problem is my US-20 input selector. US-20 is a 13 pin A/B switch.  Wehn I plug the guitar straight in, the volume goes down to 0 as it should.  through the US-20 it stops at 2.  Doesn't sound like a big issue, but believe it or not, volume setting on 2 can be pretty loud especially on distorted sounds.  Its a pain losing that control.  Now I don't know what to do b/c I can't elminate the US-20 since I need my 13 pin signal split 2 ways and need to be able to control weather only A or B or both work.  The other 13 pin signal goes to my AXON AX 100 and synth setup.  This sucks.... Anyone knows what the US-20 may be doing as to why suddenly there is a change???  THanks!
Title: Re: Volume bleed through even with knob turned to zero
Post by: ztones on March 07, 2008, 12:56:39 PM
I just got off the phone with Roland.  Nice guy, but no help there.  He could not tell me what and why the US-20 was doing this, nor offer a work around.  Anyone aware of another brand 13 pin A/B swith out there?  I am aware of the 4 way splitter by Roland, but that is not a switch.  Its just a splitter.
Title: Re: Volume bleed through even with knob turned to zero
Post by: Elantric on March 07, 2008, 01:23:59 PM
Contact Richard McClish at RMC - I recall there is a known problem with the early  RMC Preamps (not required in later models)  and the US-20  - specific with an internal US-20  Resistor to ground that needs to be modified.

http://www.rmcpickup.com/ (http://www.rmcpickup.com/)

Richard McClish <info@rmcmusic.com>
or write us at

RMC Pickup Co.
1739 Addison #15
Berkeley CA 94703

Title: Re: Volume bleed through even with knob turned to zero
Post by: Elantric on March 07, 2008, 01:54:29 PM
Found it!!
unlunf wrote:
>
> > I've read that you have to modify the US-20 to work with the RMC system.
> > Does anyone have the modifications handy? Thanks.
>
> Thankfully, the short answer is the correct one: You don't need to modify
> a US-20 for any reason when using a piezo system, no matter who made it.

-=- Greetings,

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


Richard McClish wrote>
The rest of Roland's product line up to the day of introduction of the
US-20 had a 47K pullup resistor to +5VDC on line 8 (synth volume). When
you Ground the synth volume line, this produces a drain current of 0.1mA
to flow through the resistor. In order to recreate the same conditions
in the US-20, you clip R 13 and you add a 68K between IC1 pin 5 and IC1
pin 8. Since the positive power supply to the US-20 is +7VDC, a 68K
pull-up resistor will cause approximately 0.1mA drain current when the
synth volume line is shorted to Ground. Sounds reasonable ?

BTW, 1/4 watt carbon film resistors sell for a few cents each at Radio
Shack.

Best regards,

RMC
Title: Re: Volume bleed through even with knob turned to zero
Post by: Elantric on March 07, 2008, 01:58:45 PM
Simracer & Unluf,
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
Title: Re: Volume bleed through even with knob turned to zero
Post by: Elantric on March 07, 2008, 02:08:08 PM
unlunf wrote:
>
> I note that Richard says to use a 68K component, but Lea says 470K.
> That's not the first time those two have differed on what's the
> best answer. <lol> While their underlying analyses were different,
> the net effect was the same - increase R13 to remove the problem.
> I should think that any value within the range mentioned would work
> just fine.
-=- The 68K should be a pull-up resistor to +Vcc, not just a resistance
increase.

The rest of Roland's product line up to the day of introduction of the
US-20 had a 47K pullup resistor to +5VDC on line 8 (synth volume). When
you Ground the synth volume line, this produces a drain current of 0.1mA
to flow through the resistor. In order to recreate the same conditions
in the US-20, you clip R 13 and you add a 68K between IC1 pin 5 and IC1
pin 8. Since the positive power supply to the US-20 is +7VDC, a 68K
pull-up resistor will cause approximately 0.1mA drain current when the
synth volume line is shorted to Ground. Sounds reasonable ?

BTW, 1/4 watt carbon film resistors sell for a few cents each at Radio
Shack. What's the deal with the $25. minimum purchase thing ?

Best regards,

RMC
Title: Re: Volume bleed through even with knob turned to zero
Post by: ztones on March 07, 2008, 02:14:15 PM
Wow, you are good!  Intersting stuff.  However, I believe I have the LR Baggs piezo system in my LGXT.  I just bought my LGXT last year, and you said if its post 2002 it should be RMC, but the specs that came with the guitar say that the bridge micro transducers are  L.R. Baggs.  I also just looked at Godin's website and it lists RMC bridge... I am thoroughly confused how I could have bought  this last year brand new and it came with LR BAGGS????  Unless the brochure was old... should it say RMC or LR Baggs anywhere on it?  Thanks!
Title: Re: Volume bleed through even with knob turned to zero
Post by: Elantric on March 07, 2008, 02:16:55 PM
Pop the rear control cavity cover and read who made the PC board:

They had a pile of the LR Baggs stuff in inventory that they used until depleted - then switched to RMC. So 2002 era is not a hard and fast rule for the transition date.

Here's the LR Baggs board:
https://www.vguitarforums.com/smf/index.php?topic=142.msg1903#msg1903
Title: Re: Volume bleed through even with knob turned to zero
Post by: ztones on March 07, 2008, 02:36:22 PM
Its RMC.  I guess they gave the wrong paperwork with the guitar.  Amazing!  I am glad I learned something new.  In your quote, I read that these adjustments were only for the ghost system and no adjustment is needed for the RMC or LR Baggs.  Then also, there was this line "all Poly-Drive 1 preamps have a built-in synth volume buffer, so this is immaterial in the newer instruments".  Mine def said RMC poly drive, so.... do I need to do anything with the US20 when using it with my RMC poly drive piezo?
Title: Re: Volume bleed through even with knob turned to zero
Post by: Elantric on March 07, 2008, 02:44:42 PM
>In your quote, I read that these adjustments were only for the ghost system and no adjustment is needed for the RMC or LR Baggs.


Not true


Contact Richard McClish at RMC -

http://www.rmcpickup.com/ (http://www.rmcpickup.com/)
e-mail us at
Richard McClish <info@rmcmusic.com>
or write us at

RMC Pickup Co.
1739 Addison #15
Berkeley CA 94703
Title: Re: Volume bleed through even with knob turned to zero
Post by: Elantric on March 07, 2008, 02:55:29 PM
US-20 Schematic posted

https://www.vguitarforums.com/smf/index.php?topic=434.msg1911#msg1911

https://www.vguitarforums.com/smf/index.php?topic=480.msg1919#msg1919
Title: Re: GODIN-Volume bleed through even with knob turned to zero (US-20 problem)
Post by: jazzkid74 on February 13, 2020, 06:49:35 AM
Im so happy this forum exists. :) :)

I hooked up my US-20 to facilitate cloning patches from GP-10 to VG-99 and vice versa without having to switch cables for checking the result a long the way. I hadn't used my US-20 in many years and I got a strange problem with the guitar volume on COSM guitars not going over 20% with some of my guitars with piezo and no problem with GK-3. Cleaned cables and connectors as I had read this as a tip many times here on the forum. Didn't help. Googled the forum for similar US-20 problems. And voila!
Elantric remembered something and posted a reply with info from RMC about taking out 10k R13 and solder a 68K resistor between IC1 pin 5 and IC1 pin 8.

This knowledge enabled me to solve a (for me) complicated problem, complete with googling and soldering, within one hour!

So I would like to express my gratitude to elantric and the other people on Vguitarforums for sharing your knowledge.
Title: Re: GODIN-Volume bleed through even with knob turned to zero (US-20 problem)
Post by: lazerdriver on December 20, 2021, 07:19:03 AM
I ran into a similar problem but for me it happened only when using the mag/piezo output. All controls at zero, both mag and piezo. Really only noticeable on hi-gain amp settings. If I hit a chord or note with the volumes at zero there is clean  output for a few seconds, then cuts off to silence. Seems related to the piezos somehow since it doesn't do it when just connected to the mag output.

Is this normal?
Title: Re: GODIN-Volume bleed through even with knob turned to zero (US-20 problem)
Post by: admin on December 20, 2021, 08:07:42 AM
Contact Richard McClish at RMC - I recall there is a known problem with the early  RMC Preamps (not required in later models)  and the US-20  - specific with an internal US-20  Resistor to ground that needs to be modified.

http://www.rmcpickup.com/ (http://www.rmcpickup.com/)

Richard McClish <info@rmcmusic.com>
or write us at

RMC Pickup Co.
1739 Addison #15
Berkeley CA 94703

Title: Re: GODIN-Volume bleed through even with knob turned to zero (US-20 problem)
Post by: admin on December 20, 2021, 08:23:54 AM
Quote from: lazerdriver on December 20, 2021, 07:19:03 AM
I ran into a similar problem but for me it happened only when using the mag/piezo output. All controls at zero, both mag and piezo. Really only noticeable on hi-gain amp settings. If I hit a chord or note with the volumes at zero there is clean  output for a few seconds, then cuts off to silence. Seems related to the piezos somehow since it doesn't do it when just connected to the mag output.

Is this normal?

Common on early examples with LR Baggs ,   should not occur on 2011-2020 RMC Piezo versions

Post a gut pic of electronic board. We can identify uours.
Title: Re: GODIN-Volume bleed through even with knob turned to zero (US-20 problem)
Post by: gearhound22 on January 30, 2022, 03:38:48 PM
I've noticed a strange problem with two BM guitars.

When going into my synth I can see the volume indication 0-127.

Whats happening is I'm getting a small jump either positive or negative.

When set to zero it will jump from 0-4 for example and when max it will jump around 119-127.

Same deal with the 3 way guitar/mix/synth switch.

Tried different cables but it works fine for a later BM with higher serial number....no issues there so I believe it is something to do with the guitars.

I cleaned both the 13 pin F plug and the switches with CC.

I'm using an Axon AX 50.
Title: Re: GODIN-Volume bleed through even with knob turned to zero (US-20 problem)
Post by: admin on January 30, 2022, 04:05:19 PM
Contact RMC

(See links above)
Title: Re: GODIN-Volume bleed through even with knob turned to zero (US-20 problem)
Post by: IGMartin on March 18, 2023, 08:22:53 AM
I once experienced symptoms like these and wetting sightly the pins of both ends of the 13-pin cable with WD-40 and plugging the cable in and out repeatedly both in in the guitar 13-pin jack and the GR-33 jak made them dissappear instantly!