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GX-2 GK Guitar and Unit Switcher

First ever all GK/Hex/Poly Signal Programmable Switcher,
Hex Pre-Amp, MIDI CLOCK Controller and separate string Modulator,
Semi-Arp, Poly Slow Gear, Sustainer and Enveloper. All in one unit.

NEW FIRMWARE V2.4 - New great features!
- Patch guitar select. A Patch may select a specific guitar when invoked.
- MIDI controller. GKVOL,S1,S2,CTRL1 and CTRL2 may act as MIDI sources.
- Handle ten (10) individual guitar/bass individuals: Freely map the "GK Settings" to the inputs IN1,IN2 and IN3. Each "GK Setting" contain internal volumes/sensitivities as well as which GK-SETs to use by the individual synth units (require MIDI cable). The ten "GK Settings" may be mapped differently per PATCH (overriding SYSTEM settings).
GX-2 Gear-Grinder V2 Editor (Mac OS/Windows) by GumTown is available, with firmware update feature. Click here!
GX-2 All released firmware hex files (Unzip and use with GearGrinder Editor) Click here!
Download V2.4 Reference Manual (EN) (other languages at the bottom of the page).
Download Windows GX-2 Assistant and Firmware V2.4 (also contain V1.x)


Seamless GK Guitar Switcher

GX-2 allows you to connect up to three instruments. Two GK and one regular. Switch instrument with just a stomp and keep focusing on the next song. The GX-2 will take care of normalizing the difference in guitar volume. Hex pickups as well as the regular guitar pickup

Option 1. Each individual guitar may have their separate string levels (and regular pickup) programmed into the unit to normalize their differencies in volume.

Option 2.Connect MIDI cable to your GK synth(s) to automatically switch between pre-programmed GK-Settings.

True GK Unit Selector

Connect up to two synth units (i.e. SY-1000, GR-55, GP-10 etc) with instant silent all-string mute. In contrary to other Unit Selectors the GX-2 mutes even if GK Volume knob is assigned to something else than volume.

Note: All other GK Unit selectors on the market only mute by setting the GK Volume signal to 0 Volts, this unit does it the proper way.

Expand your sound palette

Combine the built-in analog modulators effects, semi-arpeggiators, envelopers or sustainer with any existing sound of your GK-Units. Modulate volumes between the strings or between the GK Synth units. The unit hosts up to 99 effect patches.


The GX-2F (for Piezo Guitars) includes an analog Subsonic Filter board for enhanced tracking with Piezo pickups for synthesizers like Roland GR-55/VG-99(B) and older. This filter has virtually no effect with GK-Pickups/GP-10/SY-1000 and Godin Guitars with latest RMC boards.

HEX Pre-Amp

Amplify individual weak string pickups to catch up with the rest or tame very "hot" pickups. Master gain settings as well as individual string settings. There's also gain settings for the regular pickup. All gain settings are individual programmed for each guitar input.

MIDI CLOCK Controller

The GX-2 will lock to incoming MIDI CLOCK and keep the internal engine as well as your output devices syncronized to the beat.
If used without incoming MIDI CLOCK yo may use the TAP TEMPO button to set the speed of the internal engine as well as units connected to the two MIDI OUT connectors.

Source of Ultra Low Noise GK Power

The GX-2 incorporates two very low noise (4 and 16 uVRMS) DC linear LDO voltage regulators from Texas Instruments, supplying your polyphonic guitars with ultralow-noise voltage without ANY current drawn from the connected Synth Units. GX-2 power up your guitars regardless if a GK synth is connected or not.
It however require a low-noise 9VDC Power Supply (not supplied) rated >=0.5A. We recomend NUX ACD-006A or a BOSS PSA adapter.

99 Patches


Each patch may also contain individual patch-specific assigns for GK Volume, GK S1/S2, CTRL1, CTRL2 inputs and MIDI controls.

GX-2 Release notes
V2.4 2023-08-03
New: A Patch may select a dedicated guitar input (thx Fokof)
Imp: External BPM rate stabile (thx Chrissie)
Imp: Internal BPM rate stabile using timed interrupts.
V2.1 2022-11-02
Bug: INP3:Inp.setting scrolled one option too much
V2.0 2022-10-02
New: 10 mapable GK Settings instead of 3 fixed
New: Use GKVOL/S1/S2/CTRL1/CTRL2 as MIDI Controllers
New: Menu option to revert to factory settings
Bug: Fixed MIDI routing problems
Works With

Works with any 13-pin device on the market. You may put additional GK pedals before or after the GX-2.

Videos and Images

GX-2 Guitar Selector

This video shows the GX-2 as Guitar Selector. Two GK Inputs and one regular. The Synth units may be programmed to handle the shift by MIDI if required.

GX-2 Basic Operations

This video explains basic information about GX-2 functionality and connections.

Some of GX-2 Factory Patches

This video runs through the first 29 factory patches.
GX-2 Assistant
This PC software allows you to Backup and Restore the GX-2 Settings and update the GX-2 firmware (i.e. the GX-2 system program).



GX-2 firmware may be updated using the GX-2 Windows Assistant Windows PC software, or the MacOS/Windows Gumtown GearGrinder Editor. These softwares also allows you to Backup/Restore all settings. Backup is recommended before updating firmware.
You will also need a USB cable.

GX-2 Assistant V2.4 (incl. V1.x and latest V2.x)
GX-2 Assistant V1.3
GX-2 Mac OS/Windows Gear-Grinder Editor by GumTown
GX-2 All released firmware hex files (Unzip and use with GearGrinder Editor by GumTown)
Quick Guide Manual

The quick guide is only two pages

Download GX-2 Quick Guide (ENGLISH)