GR-55- Help adding DIY external guitar in, FX loop, S1/S2 switches

Started by Gastric, March 08, 2011, 05:36:13 AM

Previous topic - Next topic

0 Members and 1 Guest are viewing this topic.

Gastric

Gumtown's internal photos gave me the idea that it would be fairly easy to add some of the missing hardware features many of us would like.

* External footswitch controls for S1 / S2
* External 1/4" normal pickup input jack
* External 1/4" normal pickup effects loop

There is physically enough space to add three 1/4" jacks (and more) to the chassis.

The 13 pin input board is easily accessible with well spaced traces, and the 13 pin wiring loom is also easily accessible for splicing into which I propose is easier than soldering and cutting traces on the input board.

Note this photo does *not* have switched jacks displayed. I used my last one a couple months ago for adding an expression pedal jack to a different piece of gear.




So my proposal is this:

* Install four (4) switched 1/4" jacks (they make stacked switched jacks now to make things easier Neutrik part # NSJ12HF-1 and required nuts)
* Cut the proper wires from the 13 pin wiring loom
* Correctly connect the cut wires from the loom to the proper lugs on the switched 1/4" jacks

Note the hand drawing is just my idea, I'm clearly not an electrical engineer, though I did sleep in a Motel 6 last night. Theoretically the switched jacks would automatically connect/disconnect/insert the proper external gear into the signal chain.



Assuming this is possible, and I believe it should be, you now have the following functionality:

* Everything functions like stock when nothing is physically plugged into any of the jacks (benefit of switched jacks)
* Guitar In jack (breaks pin 7 on the 13 pin input to allow any external signal to be sent to the "normal pickup" input on the GR-55)
* FX Send / Return jacks (works with or without Guitar In)
* S1 / S2 footswitch connector (breaks pins 10 & 11 on the 13 pin input to allow external control)

And here's where my idea ends and I lobby someone with electronics experience to provide a detailed how-to for which wires to cut and how to wire the switched jacks so they function properly. :)

Even better would be some industrious company or individual manufacturing a prefabbed sub-board that has a pair of stacked switched jacks mounted to it, and a couple 13 pin wiring harness jacks, and a wiring harness cable, and a drilling template. Then all we have to do is tape the template to the back of the GR-55 chassis, drill 4 holes of the proper size, mount the jacks and jacks sub-board (can probably be held on with just the 4 jacks' mounting nuts), unplug the existing wiring harness, plug it into the jack sub-board, plug that to the GR-55 PCM and no soldering or permanent modifications required except the 4 holes in the chassis.

DML

Hey Gastric, thanks for your reply on my other thread, "GK-3 intelligence". I'm allways in for some kind of modification.
I was planning to put in an internal powersupply, exactly in the space you've mentioned above but your plan is tempting as well.
What I'm missing in the wiring is a ground or shield. Or does the outer metal ring of the 13-pin connector do the grounding? This would mean there must be OR 14 wires on the circuit board OR the casing of the GR-55 is responsible for grounding (check out the grounding screw on the back side of the GR!!).
Boss GT-1000core, Gibson Explorer 2018, Höfner travel guitar, 4x Framus Renegade Pro, Framus Panthera, Framus Panthera Custom 7, G&L Asat, Rocktron/Egnater Velocity Valve, 2x Mesa Thiele EVM12L, 2x Mesa Thiele EVM12L Road Ready, Voes MX12 midi controller, Ovation 2078TX-5 Elite, PJB Cub II - AG150.

Gastric

Here's a page detailing the GK pinouts. http://johnp.net/projects/guitar-synth/roland-pinouts.html

I didn't spend any time investigating the connections, just checking out the free space for ideas on how to add an FX LOOP to the normal pickup signal chain. There's tons of physical space unused so plenty of opportunity to install all manner of stuff in there.

gumtown

Now this is interesting !!  :o

How about an insert jack in one of the un-used GK inputs, if you use a 5 string bass, you could use one spare hex channel for a mic vocoder effect, or vocal pitch harmonies with some of the Vocal Choir sounds maybe.
Free "GR-55 FloorBoard" editor software from https://sourceforge.net/projects/grfloorboard/

Elantric

if you use search we have a good repository of the pertinent information already here:
https://www.vguitarforums.com/smf/index.php?topic=73.0


QuoteGumtown's internal photos gave me the idea that it would be fairly easy to add some of the missing hardware features many of us would like.

* External footswitch controls for S1 / S2
* External 1/4" normal pickup input jack
* External 1/4" normal pickup effects loop


For those interested, all the above can be achieved without harm to the GR-55 using a modified US-20, placed in front of the GR-55's 13 pin input:

more here:


https://www.vguitarforums.com/smf/index.php?topic=3664.0


MaxTwang

Regarding the ground question, yes it's the metal body on the 13-pin connector carries the ground signal.  The notorious eBay 13 pin cables don't use the plugs' body for ground which is why they don't work properly with Roland 13-pin devices.  These cables do have an ungrounded copper shield that can be connected to the metal body on the plugs.

I cut a 13-pin cable in 2 and have it wired to a breadboard hoping to find a way to plug a non-GK guitar into the GR-55.  Pin 9 seems to have around 7 volts regardless of the Guitar/Mix/Synth switch position, and pin 9 needs to be powered to get the GR-55 to work with a guitar on pin 7.  In my initial test I had all wires, except pin 7, connected to a GK-3 and connected pin 7 & ground to a guitar cable plugged into a strat.  I need to do more testing with pin 9, but I'm hoping to connect a 1/4" plug to pins 7 and ground and jump pins 9 and 12 to create a 13-pin to 1/4" guitar input for the GR-55.  If this works and I'm feeling adventurous I might try adding the buffering found in the GK-2a schematic (see below).

You can connect a guitar's output to pin 7, but the tone will be different from connecting through a GK-3.  The GK-3 appears to buffer the guitar input (see GK-2a schematic in the link above, there's a couple resistors, a capacitor and 1/2 of an opamp on the guitar input).  On clean sounds the direct guitar sounded warmer, but with overdrive the direct guitar sounded fizzy compared to the guitar through a GK-3.

gumtown

Quote from: MaxTwang on March 10, 2011, 01:35:48 PM
I cut a 13-pin cable in 2 and have it wired to a breadboard hoping to find a way to plug a non-GK guitar into the GR-55.  Pin 9 seems to have around 7 volts regardless of the Guitar/Mix/Synth switch position, and pin 9 needs to be powered to get the GR-55 to work with a guitar on pin 7.  In my initial test I had all wires, except pin 7, connected to a GK-3 and connected pin 7 & ground to a guitar cable plugged into a strat.  I need to do more testing with pin 9, but I'm hoping to connect a 1/4" plug to pins 7 and ground and jump pins 9 and 12 to create a 13-pin to 1/4" guitar input for the GR-55.  If this works and I'm feeling adventurous I might try adding the buffering found in the GK-2a schematic (see below).

You can connect a guitar's output to pin 7, but the tone will be different from connecting through a GK-3.  The GK-3 appears to buffer the guitar input (see GK-2a schematic in the link above, there's a couple resistors, a capacitor and 1/2 of an opamp on the guitar input).  On clean sounds the direct guitar sounded warmer, but with overdrive the direct guitar sounded fizzy compared to the guitar through a GK-3.
Yes you will need to add the buffering circuit as found in the GK-3/GK-2A to the Normal PU signal, the difference in sound may be due to the buffer providing impedance matching to the GR-55 input, where if you use a passive guitar signal, can make a big difference to the tone if wiring directly into the GR-55 unbuffered.
The 7volts is the power supply for the buffer amplifiers inside the GK units, you could use that and replace the buffer on your breadboard.
Free "GR-55 FloorBoard" editor software from https://sourceforge.net/projects/grfloorboard/

ddlooping

If I wanted to only add two mono or one stereo jack connector(s) to control S1 and S2 with foot-switches, could I just expose some of the pin 10 (?) and 11 (?) wires so as to solder the wires going to the jacks to them (piggy-backing)?



Diaz Guitars (work in progress)

gumtown

Quote from: ddlooping on March 10, 2011, 07:19:07 PM
If I wanted to only add two mono or one stereo jack connector(s) to control S1 and S2 with foot-switches, could I just expose some of the pin 10 (?) and 11 (?) wires so as to solder the wires going to the jacks to them (piggy-backing)?

Yes, but you might want to use 1k ohm resistors instead of wire links, just to keep it the same as the S1/S2 switches in the GK, and the 0.01uF capacitor across the jack too.
It will work without those items, but probably not quite as reliably and clean switching.
If the GR-55 chassis is not at the same potential as the GK ground, and your Jack sockets have an insulated mounting hole, you might want a common ground connection to the GK input board ground point too.
I am not sure if having the metal jack sockets 'connect' with the GR-55 chassis will cause any ground loop problems, just try it and see.
Free "GR-55 FloorBoard" editor software from https://sourceforge.net/projects/grfloorboard/

ddlooping

Alternatively, I could cut the wires in the middle and use one of these...



... to reconnect them together while inserting the wires going to the jack connectors. (two wires per hole on one side, one per hole on the other).
Diaz Guitars (work in progress)

gumtown

Quote from: ddlooping on March 10, 2011, 07:29:03 PM
Alternatively, I could cut the wires in the middle and use one of these...



... to reconnect them together while inserting the wires going to the jack connectors. (two wires per hole on one side, one per hole on the other).

ARRRGGHH !! i absolutly loath chocky block connectors in audio equipment, best to solder directly on top the GK input board terminations where the other original wires are soldered.
Free "GR-55 FloorBoard" editor software from https://sourceforge.net/projects/grfloorboard/

ddlooping

Quote from: gumtown on March 10, 2011, 07:28:35 PM
Yes, but you might want to use 1k ohm resistors instead of wire links, just to keep it the same as the S1/S2 switches in the GK, and the 0.01uF capacitor across the jack too.
It will work without those items, but probably not quite as reliably and clean switching.
If the GR-55 chassis is not at the same potential as the GK ground, and your Jack sockets have an insulated mounting hole, you might want a common ground connection to the GK input board ground point too.
I am not sure if having the metal jack sockets 'connect' with the GR-55 chassis will cause any ground loop problems, just try it and see.

Thanks gumtown. :)

If I understand you correctly that'd mean adding a 1k resistor in series with the extra wires (in case the resistor is not long enough to reach the sockets' "+" connectors), and bridging the "+" and ground connectors on the sockets with a 0.01uF capacitor, right?
Diaz Guitars (work in progress)

ddlooping

Quote from: gumtown on March 10, 2011, 07:32:58 PM
ARRRGGHH !! i absolutly loath chocky block connectors in audio equipment, best to solder directly on top the GK input board terminations where the other original wires are soldered.

I'd rather not touch the soldering on the board. :)
I think it'd be pretty clean and safe to just expose some of the original wire(s) and solder the new wire(s) to it(them).
Some nicely applied electrical tape would then protect the assembly.
It'd also have the advantage of being easily reversible.
Diaz Guitars (work in progress)

gumtown

Quote from: ddlooping on March 10, 2011, 07:34:20 PM
Thanks gumtown. :)

If I understand you correctly that'd mean adding a 1k resistor in series with the extra wires (in case the resistor is not long enough to reach the sockets' "+" connectors, and bridging the "+" and ground connectors on the sockets with a 0.01uF capacitor, right?
Yes, correct. What i do id strip some insulation off a bit of wire and slide it over the two resistor tails, so there is less exposed metal, and the resistor tails should be long enough to reach the sockets.
Free "GR-55 FloorBoard" editor software from https://sourceforge.net/projects/grfloorboard/

ddlooping

Quote from: gumtown on March 10, 2011, 07:38:47 PM
Yes, correct. What i do id strip some insulation off a bit of wire and slide it over the two resistor tails, so there is less exposed metal, and the resistor tails should be long enough to reach the sockets.

Thanks again. :)
Diaz Guitars (work in progress)

ddlooping

Would a stereo connector like the following work?



All metal so it'd be grounded to the chassis.

Or would a plastic one be best, so it's not grounded to the chassis?

Diaz Guitars (work in progress)

ddlooping

Diaz Guitars (work in progress)

gumtown

Either socket will work, I would be more inclined to the insulated one, best to only have one point of earthing to the chassis.
And run a common earth wire from the GK sub-board wiring loom.
The polyester capacitor will do fine too.
A single stereo socket for both S1 & S2 will also work, where you could use something like the Boss FS-6 dual footswitch with a single stereo (TRS type) cable.
Free "GR-55 FloorBoard" editor software from https://sourceforge.net/projects/grfloorboard/

ddlooping

Thanks again. :)

I might take the plunge very soon.
I just need to make sure I can clearly identify the two wires.
Diaz Guitars (work in progress)

tomtheguitarguy

http://www.tomtheguitarguy.com ~ http://www.tomcatsband.com
CIJ Blue Floral w/ McVay G Bender
G & L Will Ray Signature ASAT w/ Hipshot B Bender
JTV-69 James Tyler Variax
Fishman TriplePlay ~ Roland GR-55
Dr. Z RxES 2x12
Quilter MicroPro200 10" ~ Quilter Aviator 8" ~ Quilter Steelaire
Bose L1 Classic

Elantric

Quote
Any progress on the MAGIC BOX, Elantric?

Thanks!

For those interested, all the above can be achieved without harm to the GR-55 using a modified US-20, placed in front of the GR-55's 13 pin input:

more here:


https://www.vguitarforums.com/smf/index.php?topic=3664.0


tomtheguitarguy

Quote from: Elantric on February 21, 2012, 03:10:34 PM
Its on hold for the moment.

My projected MagicBox sales did not meet the minimum R&D budget for this.

Thanks!

I guess I'll go ahead and order the parts to see if I can make something similar then.

Tom
http://www.tomtheguitarguy.com ~ http://www.tomcatsband.com
CIJ Blue Floral w/ McVay G Bender
G & L Will Ray Signature ASAT w/ Hipshot B Bender
JTV-69 James Tyler Variax
Fishman TriplePlay ~ Roland GR-55
Dr. Z RxES 2x12
Quilter MicroPro200 10" ~ Quilter Aviator 8" ~ Quilter Steelaire
Bose L1 Classic

teleholic

Very nice Mark! Not only your product but your video looks so professional, it totally looks and sounds like a Roland promo..haha

neophytte

I saw this on eBay and got all excited, but I just finished my Septar kit ... and the shipping to Aust. killed it for me :(

Cheers

Richard

drjoness2001

I'm not sure what's up with that, it's 2-3 lbs, USPS Priority Mail, but when I checked just now with USPS, the price was $42!

Is it jet fuel or what, I can't believe the cost is so high, and they eliminated surface mail.

Quote from: neophytte on June 26, 2012, 04:32:29 AM
I saw this on eBay and got all excited, but I just finished my Septar kit ... and the shipping to Aust. killed it for me :(

Cheers

Richard