Author Topic: GR-55 guitar pickup input output fx loop Mod with Pictures!  (Read 37814 times)

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Offline Beirne

I just added a guitar pickup output jack and guitar 1/4" input jack to my GR-55. Lets you use external fx to the normal guitar pickup and routes it back in to the GR55 for mixing. This mod basically hijacks the regular guitar pickup connection to the 13pin jack on the unit and adds one switching 1/4 jack and one regular jack. It also lets you set up a patch for normal pickup only to use some of the GR55 Effects with a non roland guitar, just in case your roland guitar breaks or you dont want to bring extra fx for a second non-roland regular bass/guitar.
Fairly easy mod, took me a leisurly hour.
Pictures are worth a thousand words.

Parts-  1/4 switching jack, plain 1/4 jack. 8" of thin wire.
solder, drill, tape to place in unit to keep metal filings from getting on the circuits.

Cheers, Beirne
check out my music and free album download
 www.intangiblesny.com

===================

Observe the RED "A", "B", "C" labels on both schematic and pic below!

A = FX Send Jack "TIP" connection

B = FX Return switching Jack "Tips' Normally Closed contact " connection

C = FX Return Jack "TIP" connection




Here is a labeled version of the Jacks used in the   GR-55 guitar pickup input output fx loop Mod with Pictures



A = FX Send Jack "TIP" connection

B = FX Return switching Jack "Tips' Normally Closed contact " connection

C = FX Return Jack "TIP" connection


Read the GR-55 Gk Input Reference thread
http://www.vguitarforums.com/smf/index.php?topic=12249.msg89023#msg89023















« Last Edit: April 04, 2016, 05:48:33 PM by Elantric »

Offline audiotrax

Re: GR-55 guitar pickup input output fx loop Mod with Pictures!
« Reply #1 on: June 06, 2011, 07:05:52 AM »
Beirne: I just checked out your Intangibles page - the album cover artwork is priceless!  The robot even has a belly "button".  The music is good too  :)
Owner of: VG-88, GI-10, Cubase 5, Kontakt, SampleTank, var VSTI's, Roland JV1080.  Strat with GK-2A, two Roland GR500 analog guitar synths

Offline res075oh@gte.net

Re: GR-55 guitar pickup input output fx loop Mod with Pictures!
« Reply #2 on: June 06, 2011, 10:11:45 PM »
That looks great.  A few questions:  1] Am I reading you correctly that you can plug a regular guitar into one of the jacks and the effects of the GR55 will be applied and output?  2] It appears the switched jack switch is normally closed, right?  3] Do you have a schematic?

Thanks,
James
.
.



I just added a guitar pickup output jack and guitar 1/4" input jack to my GR-55. Lets you use external fx to the normal guitar pickup and routes it back in to the GR55 for mixing. This mod basically hijacks the regular guitar pickup connection to the 13pin jack on the unit and adds one switching 1/4 jack and one regular jack. It also lets you set up a patch for normal pickup only to use some of the GR55 Effects with a non roland guitar, just in case your roland guitar breaks or you dont want to bring extra fx for a second non-roland regular bass/guitar.
Fairly easy mod, took me a leisurly hour.
Pictures are worth a thousand words.

Parts-  1/4 switching jack, plain 1/4 jack. 8" of thin wire.
solder, drill, tape to place in unit to keep metal filings from getting on the circuits.

Cheers, Beirne
check out my music and free album download
 www.intangiblesny.com

Offline FreeTime

Re: GR-55 guitar pickup input output fx loop Mod with Pictures!
« Reply #3 on: June 07, 2011, 02:35:40 AM »
I was going to do something very similar until I read something about some impedance matching going on in the GK3, I'm curious Beirne, how is the sound with a guitar plugged straight into the new input jack ? If it sounds muffled then perhaps an impedance matching transformer or op amp might fix it.

I really like the music !!!

Offline gumtown

Re: GR-55 guitar pickup input output fx loop Mod with Pictures!
« Reply #4 on: June 07, 2011, 02:47:32 AM »
I was going to do something very similar until I read something about some impedance matching going on in the GK3, I'm curious Beirne, how is the sound with a guitar plugged straight into the new input jack ? If it sounds muffled then perhaps an impedance matching transformer or op amp might fix it.

I really like the music !!!
I think the mod was intended to run an external guitar effects processor on the normal PU tone and feed that back into the Normal PU of the GR-55.
That would mean the signal is buffered from the GK-3 to the external FX, and the return signal is also buffered from the FX unit, so there should be a good impedance match there.

But running a passive guitar mono cable directly into the Return does also interest me, i would think an active stage would be required.
What would be curious is if a switch could be added to connect the Normal PU return to a hex input channel reserved for the GK-3 pickup, and having monophonic Modeling and PCM synth from a normal guitar. I think this would be possible.

I do like the mod shown here, great job !!  ;)
Free "GR-55 FloorBoard" editor software from http://sourceforge.net/projects/grfloorboard/

Offline Elantric

Re: GR-55 guitar pickup input output fx loop Mod with Pictures!
« Reply #5 on: June 07, 2011, 07:43:32 AM »
Quote
If it sounds muffled then perhaps an impedance matching transformer or op amp might fix it.

Or simply insert any Boss pedal (TU-3, CS-1,DS1,etc) between your passive guitar and this new 1/4"  FX Return jack. Even when these are in "bypass"  - they will always buffer the guitar signal and lower the impedance.

Instead of drilling holes in the main GR-55 Chassis, i would have fabricated an I/O plate to replace the black plastic USB drive panel,

Then place all the new 1/4" jacks and the USB type A Host jack (that used to be on the black plastic plate) on this new I/O plate - so all could be reverted to stock in 2014 when its time to sell the old GR-55 to buy a newer improved  version which will surely arrive.

Back in 1997 I had a very modified Boss GT-5, with additional jacks for remote foot switches but in 2003 when I wanted to sell it, nobody wanted it  - since it was no longer "stock".

For this reason is why I prefer to keep the GR-55 stock ( = higher resale value) and make my FX Loop mods to a Roland US-20 instead. 
Magic Box Mod for US-20
http://www.vguitarforums.com/smf/index.php?topic=7245.0
« Last Edit: August 21, 2013, 12:31:52 AM by Elantric »

Offline Beirne

Re: GR-55 guitar pickup input output fx loop Mod with Pictures!
« Reply #6 on: June 07, 2011, 09:49:40 AM »
-Yes regular guitar in works. You may need to edit the preset so the regular guitar is routed to the fx.
-If your guitar or bass has active (9vbattery inside) pickups it works fine, or if yo put any sort of fx pedal before the input that works too, Otherwise the volume may be a bit low.
-switched jack is normally closed
- schematic...if you need one then you shouldnt attempt this mod. But if you study the pics and buy the same jacks it should be simple.


That looks great.  A few questions:  1] Am I reading you correctly that you can plug a regular guitar into one of the jacks and the effects of the GR55 will be applied and output?  2] It appears the switched jack switch is normally closed, right?  3] Do you have a schematic?

Thanks,
James
.
.

Offline Beirne

Re: GR-55 guitar pickup input output fx loop Mod with Pictures!
« Reply #7 on: June 07, 2011, 10:04:55 AM »
The usb drive slot is a nice feature and I didnt want to negate it. Plus its all the way on the other side of the outputs. Anyway, I usually get good prices for my used modded gear. Just point out the pros in your ebay ad. And do a neat job and lable your inputs.
 I use a 1/4 guitar cable wrapped alongside the 13pin cable (along with a mic cable for my headset mic!) so I dont use the modded 1/4 out, only the 1/4 in switching jack. This way I can switch to a regular guitar/bass when needed, and I have a few gr55 presets setup for this. Also works out for me if the GK pickup/cable dies (has happened) and I can easily go into regular guitar cable mode. I put a boss vf1 fx unit on the regular guitar before the gr55. I find the gr55 doesnt have enough fx chain in it.

Or simply insert any Boss pedal (TU-3, CS-1,DS1,etc) between your passive guitar and this new 1/4"  FX Return jack. Even when these are in "bypass"  - they will always buffer the guitar signal and lower the impedance.

Instead of drilling holes in the main GR-55 Chassis, i would have fabricated an I/O plate to replace the black plastic USB drive panel,

Then place all the new 1/4" jacks and the USB type A Host jack on this new I/O plate - so all could be reverted to stock in 2014 when its time to sell the old GR-55 to buy a newer improved  version which will surely arrive.

Back in 1997 I had a very modified Boss GT-5, with additional jacks for remote foot switches but in 2003 when I wanted to sell it, nobody wanted it  - since it was no longer "stock".

Offline Albert

Re: GR-55 guitar pickup input output fx loop Mod with Pictures!
« Reply #8 on: June 11, 2011, 11:52:53 PM »
Great modification! Might do it myself as well. Thnx for the pics!

Offline Beirne

Re: GR-55 guitar pickup input output fx loop Mod with Pictures!
« Reply #9 on: June 20, 2011, 10:47:13 PM »
It's a fairly simple mod. You dont have to remove the 13pin input jack and jumper board like I did, but it makes soldering etc easier. Just take care removing the jumper connector...there are tiny pins that need to be depressed and eased out with a tiny flat blade screwdriver...the connector is VERY tight to the board. If I had to do it again I would just cut the wires and splice in place without disturbing anything.

It would have been so easy for roland to add this. Oh well, at least theres plenty of space inside for all sorts of stuff.

Offline Guitarbot

Re: GR-55 guitar pickup input output fx loop Mod with Pictures!
« Reply #10 on: June 21, 2011, 03:50:02 PM »
This mod will allow me to plug my guitar into my fx unit, then send the fx mono out into the gr-55 & then output the signal via usb to my computer for recording correct?  (ie: I can use the gr-55 as my usb audio interface.)

Offline gumtown

Re: GR-55 guitar pickup input output fx loop Mod with Pictures!
« Reply #11 on: June 21, 2011, 04:15:11 PM »
This mod will allow me to plug my guitar into my fx unit, then send the fx mono out into the gr-55 & then output the signal via usb to my computer for recording correct?  (ie: I can use the gr-55 as my usb audio interface.)
Yes you could do that,
you could also plug your guitar jack directly to a multi/external effects and plug the effects output back into the GK input too, without a need for the GR-55 mod, but the mod will keep things tidy and on the floor.
Free "GR-55 FloorBoard" editor software from http://sourceforge.net/projects/grfloorboard/

Offline Guitarbot

Re: GR-55 guitar pickup input output fx loop Mod with Pictures!
« Reply #12 on: June 21, 2011, 07:28:13 PM »
Good point gumtown.  I hadn't thought about that.  Thank you for your inputs!

Offline Gastric

Re: GR-55 guitar pickup input output fx loop Mod with Pictures!
« Reply #13 on: June 30, 2011, 12:53:22 PM »
Awesome, I've been waiting for someone to do this. :)


Offline Gastric

Re: GR-55 guitar pickup input output fx loop Mod with Pictures!
« Reply #14 on: July 03, 2011, 08:34:12 AM »
I was all out of switched 1/4" TRS jacks so I had to order some more which should be in next week. Is there any potential ground issues using an external guitar with the jacks as wired? I ask as the switched jacks I ordered are slightly different and plastic, not metal. Thus the jack won't be connected to the chassis unless I specifically wire a ground.

Offline Elantric

Re: GR-55 guitar pickup input output fx loop Mod with Pictures!
« Reply #15 on: July 03, 2011, 11:44:37 AM »
The jacks with plastic isolation are preferred. This is an unbalanced audio path and is extremely prone to ground loop hum. The metal chassis is typically prone to contributing to noise if your jacks make direct contact. Instead, solder  your new Jack's ground connection to the Ground wire on the existing internal 13 pin jack board. The 13 pin connector "Shell " connection tab is Analog Ground - use that to locate the proper internal wire connection.
« Last Edit: July 03, 2011, 03:45:46 PM by Elantric »

Offline Gastric

Re: GR-55 guitar pickup input output fx loop Mod with Pictures!
« Reply #16 on: July 21, 2011, 03:28:28 PM »
I've implemented a Send / Return on my GR-55, though I haven't committed to drilling the two jacks into the chassis yet as I don't have the appropriate drill bit.

When using plastic jacks it definitely requires the jacks to be grounded to the GR-55 otherwise you get horrible hum, as expected. There's a ton of ground points, including nearly all of the board screw mounts so I currently just have the ground sandwiched to the board that way VS soldering at this time.

Anyway, it is fully functional as conceived. However, when running a non-GK instrument directly into the Return the instrument loses a ton of volume and high end, unbearably so. Run the instrument into a BOSS OC-2 to utilize it's buffer and the volume loss is corrected but there's still a roll off on the tone, though less so. Run the same instrument into the BOSS OC-2 then into the 1/4" jack on the GK controller and it sounds great. So there's definitely some tone issues with this modification.  I'm not sure what other buffered pedals I have available to try, but I'll flip through whatever I have to see if one applies a better correction than others.

Offline gumtown

Re: GR-55 guitar pickup input output fx loop Mod with Pictures!
« Reply #17 on: July 21, 2011, 04:42:33 PM »
The GR-55 input definately requires a buffer/amplifier, since this is built into the GK unit.
The lost of high end will also be due to an impedance mismatch, the signal in the GK cable would be low impedance (approx 100 ohms or so) to give it better noise immunity.

I see you used a fairly heavy gauge solid conductor wire for your mod... :-/ be careful bending it around inside the case.
« Last Edit: July 21, 2011, 05:19:53 PM by gumtown »
Free "GR-55 FloorBoard" editor software from http://sourceforge.net/projects/grfloorboard/

Offline Gastric

Re: GR-55 guitar pickup input output fx loop Mod with Pictures!
« Reply #18 on: July 21, 2011, 06:15:16 PM »
Electronics gurus - what's the easiest way to apply a 100ohm buffer to a dry input? I was hoping the BOSS pedal would magically do that.

It's 18 gauge solid core wire, what I had on hand. Easy enough to replace, though I don't foresee any reason to. While it's fairly stiff, the good news is it stays where you bend it which is just fine for permanent installations.

Offline gumtown

Re: GR-55 guitar pickup input output fx loop Mod with Pictures!
« Reply #19 on: July 21, 2011, 07:09:37 PM »
Try building this into the GR-55, it is a copy of the GK guitar buffer circuit, you could use almost any low noise opamp chip

You could also try substituting R19 (10k) resistor for something closer to 100k if you have a passive output guitar, to bring the input impedance up closer to that of the guitar pickups.
« Last Edit: July 21, 2011, 07:14:11 PM by gumtown »
Free "GR-55 FloorBoard" editor software from http://sourceforge.net/projects/grfloorboard/

Offline Gastric

Re: GR-55 guitar pickup input output fx loop Mod with Pictures!
« Reply #20 on: July 21, 2011, 07:48:18 PM »
Note the OC-2 in the FX send/return also affects the tone. This very well may simply be how the OC-2 affects the tone no matter how/where/when it's inserted into the signal chain. I honestly haven't compared the before/after of inserting the OC-2 into the chain before. Right now I can only say the following:

1. Using the GK instrument with the OC-2 in the FX loop sucks some tone
2. Using a non-GK instrument directly into the FX return sounds terrible, I wouldn't use it
3. Using a non-GK instrument into the OC-2 then into the FX return seems to sound about the same as #1 above

So it's possible it's the OC-2 that's sucking the tone and not the straight wired FX send / return.  I'll test further and try to get some recordings for everyone to review.  With the huge true bypass rage it's actually hard to come up with buffered pedals, and my pedal collection is small thanks to BOSS/Roland's multi boards. ;)

Offline Gastric

Re: GR-55 guitar pickup input output fx loop Mod with Pictures!
« Reply #21 on: July 21, 2011, 08:48:14 PM »
Quick MP3. You be the judge and let me know what you think.


* Lakland 44-60 4 string jazz bass strung with GHS piccolo strings, bridge pickup soloed, tone on full, played like a guitar as best I can for all you guitar players.
* No amps, effects, processing, just raw "normal pickup" out to GR-55 USB and recorded, then normalized which boosts volume to highest peak (and probably masks some of the volume discrepancies which can probably be similarly controlled via normal pickup volume in the patch)
* Normal pickup into GK controller
* Normal pickup into GK controller with BOSS LS-2 with channel A slightly boosted in FX send/return loop
* Normal pickup directly into BOSS LS-2 with channel A slightly boosted into FX return (bypasses GK controller totally)
* Normal pickup into BOSS OC-2 into FX return (bypasses GK controller totally)
* Normal pickup into FX return (oh! the horror!) (bypasses GK controller totally)

I was playing through amp sims, etc earlier. Decided to turn everything off and just solo the raw input for the best comparison. It's late, I've been at this a while, and have half a pitcher of margaritas in me. At this point I think it all sounds pretty good except the instrument directly into the FX return which I still think sounds like doo-doo.  I swear the OC-2 was seriously sucking my tone before, but listening to the clip it doesn't sound so drastically bad as I thought.
« Last Edit: July 21, 2011, 09:17:20 PM by Elantric »

Offline Beirne

Re: GR-55 guitar pickup input output fx loop Mod with Pictures!
« Reply #22 on: July 22, 2011, 09:34:45 PM »
My basses and guitars all have active pickups (and 9v batteries/preamps) so I havent found any issues with tone when inputting directly on the GR55.

Offline ProgMystic

Re: GR-55 guitar pickup input output fx loop Mod with Pictures!
« Reply #23 on: July 22, 2011, 11:51:41 PM »
Beirne,

I have the VG-99 so your mod is of only passing interest, your album on the other hand is just fantastic!! 8) I will be pushing that on everyone I talk to. I certainly hope you are selling plenty, the groove is just awesome. Great band!
Once I thought I was wrong, but I was mistaken.

Offline Beirne

Re: GR-55 guitar pickup input output fx loop Mod with Pictures!
« Reply #24 on: August 20, 2011, 10:54:17 AM »
Beirne,

I have the VG-99 so your mod is of only passing interest, your album on the other hand is just fantastic!! 8) I will be pushing that on everyone I talk to. I certainly hope you are selling plenty, the groove is just awesome. Great band!

THANKS!!
free download here and friend us on facebook too...   intangiblesny.com

 

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