ebay for sale
Updates: April 2014
IMG2010 Magazine Advertising: Lost IMG2010 full-page advertising page found! New resource with six full-page vintage IMG2010 ads.

IMG2010 Update: New photos, expanded videos and more!
Roland GK-1

Roland GK-1 Synthesizer Driver

Features and Specifications:

Compatible with GM-70, GR-700, GR-300, GR-100, MC1 and Korg Z3
Volume Control
Balance Control
2 - Continuous Controllers, CV#1 (filter) and CV#2 (resonance)
GR Connection cable (5m 24 pin connector)
Normal Guitar Input Jack
6 - Output Adjusting Knob
Accessories include parts for installation
Weight: 428g/15 oz (including GR Connection Cable)

Pat Metheny with Roland GK-1
Pat Metheny with a GK-1 unit holder mounted just below the bridge of his Gibson ES-175 guitar.

Introduction to the Roland GK-1 Synthesizer Driver:

After a decade of building their own proprietary guitar synthesizers and guitar synthesizer controllers, Roland changed directions with the release of the GK-1 Synthesizer Driver and the Roland GM-70. The GK-1 and GM-70 were frequently packaged together as the new Roland guitar synth system that worked with any guitar, and enabled the guitarist to play any MIDI synthesizer.

Of course the GK-1 worked with the preceding Roland GR synthesizers, like the GR-100, GR-300 and GR-700, but the Roland GM-70/GK-1 brochure emphasized using the GM-70/GK-1 with the newer Roland MKS modules. Roland highlighted the use of MIDI Mode 4, omni off/mono, designed with guitar players in mind. MIDI modes, once an important consideration when buying MIDI gear, have been pretty much forgotten about.

Pat Metheny with Roland GK-1
Heavy Metal Virtuoso Ritchie Blackmore with a GK-1 attached to his Fender Stratocaster.

The GK-1 divided pickup has a small enough profile so it can be mounted on almost any guitar, unlike the earlier Roland designs that often required routing parts of the guitar body to make sufficient room for the bulky divided pickups.

The basic GK-1 package consisted of the divided pickup and GK-1 synthesizer driver with attached G 24 BUS cord. Permanently attaching the cable to the driver eliminated the need for a bulky 24-pin connector on the guitar, but it also meant that a player would not be able to have spare cables on hand. And unfortunately the 24-pin connector used for the C 24 Bus cord is the dreaded, plastic potted assembly, which is impossible to repair when failures occur. After 25 years of service, many of the GK-1 systems are failing due to breaking cables, leaving a lot of dead GK-1 systems.

GK-2 with GK-1 Pickup1
Early GK-2 with GK-1 pickup

An interesting note: the original GK-1 pickup would later be renamed the GK-2 pickup, and was the first pickup used by Roland in the GK-2, 13-pin system.

Soon after, Roland developed an entirely new pickup for the 13-pin generation, the GK-2A, followed by the GK-3. The GK-2A is very well known, installed as a permanent kit on many guitars, and in the top mount GK-2A system, but you can still find a few GK-2 systems with the older, Roland GK-1 pickup in use.

GK-1 Controllers and Mode Limitations:

GK-1 ControlsTo maintain the compact size of the GK-1 system, Roland opted to remove many of the continuous controllers used in the vintage 24-pin systems. The GK-1 offer four controls: volume, balance, continuous controllers #1 (filter) and #2 (resonance).

By supporting controllers #1 and #2, the GK-1 could be used with the Roland GR-100 and GR-300 to control the VCF cutoff and resonance. With the GR-700, these controllers can be used for essential editing functions.

Missing from the GK-1 is anyway to control modulation, or controller #4. Also, the GK-1 defaults to "Mode 2." With the GR-100, Mode 2 is the standard hexaphonic fuzz sound. Mode 3 is required to access the saturated, enhanced sustain fuzz sound.

GK-1 Kit with BoxWith the GR-300, Mode 2 is the "Distortion (hex fuzz) + VCO (synth)" setting. Since the GK-1, like the G-707, does not offer a hex fuzz output, only the VCO synth sound is heard with the GR-300. In this regard, using the GK-1 with the GR-300 is a bit like playing the GR-300 in Mode 3, but without the GR-300 string select feature. The GR-300 string select feature allows a player to turn individual strings synth sound on or off.

The String Select feature is useful for doubling a synth bass sound only on the lower strings of the guitar, like "E" and "A", or for voice leading with the higher strings, like "B" and "E". The GK-1 can be modified for Mode 3 operation. See below.

With the GR-700, Mode 2 is the standard synth response setting. Mode 3 on the GR-700 is used for playing the GR-700 with a lighter, faster touch.

Links to more information:

Download the Updated GK-1 Owner's Manual with information on trimmer adjustment (pdf).


Click on any image for larger view.



Mode Select Modification

GK-1 ModificationGK-1 owners do not have access to the String Select feature of the GR-300. String Select refers to the bank of six switches that turn the synth tone on or off for each string. A check of the schematic shows that String Select is tied to the Mode switch.

The GK-1 does not have a Mode switch. In fact, the GK-1 is hard wired in Mode 2. My simple modification changes the GK-1 from Mode 2 to Mode 3. Just solder a jumper wire from pin "1", the positive 15 volt supply, to pin "15" the Mode select pin. GK-1 owners will find that their system operates exactly as before, except you can now use the String Select feature!

Plugging a simple foot switch into the String Select jack on the back of the GR-300 will disable the String Select feature, activating all the strings again!

GR User Harry Bissell has a great suggestion for adding a mode switch to the GK-1: install a switch in place of the miniature input jack for the guitar. All that is needed is a SPDT switch, with a middle off position. Run the output of pin "1" (+15) to the center pin of the switch, and connect pin "16" (Mode 1) and pin "15" (Mode 3) to the other pins. In addition, solder a 10K resistor from pin "15" and pin "16" to ground. This will duplicate the existing Mode switch on a GR-series guitar.

GK-1 Divided Pickup Replacement - G-VOX Divided pickup

The delicate GK-1 divided hex pickup can easily be damaged. Unfortunately, due to the nature of the tiny, delicate wiring, it is almost impossible to repair. The Fender/G-VOX pickup can be used as a replacement for the original GK-1 pickup. I have done this modification several times, and it works well. I have also used the G-VOX pickup as a replacement for the STK-1 electronics kit as well.

Roland GK-1 to Fender/G-VOX Wiring Diagram.

G-VOX Pickup Mounting Instructions.

Click on any image for larger view.

Fender G-VOX pickup installed for use with STK-1/LPK-1 or G-202/303/505/707/808 Electronics

Click on any image for larger view.

Schematics - Repairs - Service Bulletins:

There are no known service bulletins from Roland addressing any GK-1 problems.

Download the GK-1 Service Manual Schematics.

Notes on Adjusting the GK-1 Output Level.

GK-1 Magazine Advertising:

There are examples of GK-1 advertising and a comprehensive product brochure on the GM-70 page.