The RK-002 ‘Smart MIDI cable’ has already found it’s way in various setups (not just with the volca Sample)

Buy the RK-002

Popular uses

  • Add 1-channel sample triggers with velocity and polyphonic play on multiple MIDI channels for the volca Sample
  • Adds arpeggiator functionality to existing MIDI data
  • Adds KORG volca FM velocity sensitivity
  • Add extra parameter control to Roland Boutique Synths
  • Add polyphony to the Elektron Digitakt
  • …and much more…

Watch Sonicstate’s Nick and Gaz having a ball with the RK-002 (2016)
Mind you the RK-002 now is shipped with a new orange plug end as opposed to the version in the video. Also we have increased the length to 1.5m and the RK-002 is able to run custom firmware for multitude of other MIDI devices.

The RK-002 ‘Smart MIDI cable’ has already found it’s way in various setups, not just for the volca Sample. It looks like a +/-1.5m ordinary  male-male MIDI-cable but has a microprocessor on board which ‘bends’ midi data on the fly.

Initially developed to solve the KORG volca Sample’s MIDI behaviour but in the meantime various other firmware flavours have come to life:

  • Digitakt firmware Details
    The Digitakt firmware adds polyphony, euclidian rhythms and an arpeggiator to the Elektron Digitakt. By default set to use with the RK002 in loopback mode to make use of the Digitakt’s own sequencer but also useable for exernal play.
  • MOD firmware (volca FM velocity fix, Digitakt polyphony or …) Details
    Actually not only to add velocity data to the volca FM – it’s a more versatile firmware version which is able to add extra controller mapping to key, aftertouch, pitch and modulation. This can come in handy on various MIDI devices.
  • Volca Sample firmware Settings
    Adds single MIDI channel sample triggering, velocity, polyphonic play capabilities and more to the Volca Sample
  • Arpeggiator firmware Settings
    Adds arpeggiator capabilities to your MIDI
  • KORG Kaossilator firmware Details
    This firmware allows you to play the KORG Kaossilator from a regular MIDI keyboard.

And some with a bit more experimental nature:

  • MIDI -> Sync firmware Settings
    Instead of putting MIDI out signal, in this firmware the RK-002 sends a clock out signal. The clock can be a partial of the received MIDI clock, much alike the RK-004 Clock processor and RK-006 master hub
  • MIDI -> Video firmware Settings
    With this firmware you can play lo-res video images via a regular MIDI keyboard.


The RK002 firmware is updatable via MIDI, you can implement the RK-002’s sysex messages in e.g. a MIDI controller or visit the firmware parameter-settings pages. Firmware update can also be done from the browser via the DUY Exchange Portal.


To keep things portable and solderless we decided to make the RK-002 MIDI-Powered. This means the embedded controller is powered by the MIDI bus and you don’t need an extra power supply. Beware though: Although power consumption is very, very low: Not every MIDI interface or device supports MIDI power! In order to make the RK-002 work in these cases there are multiple options, but if you want to work with what you have at hand; Sometimes looping the RK-002 through another synthesizer’s MIDI-In -> MIDI-Thru port can solve the problem. Our RK-006 USB MIDI Interface / Standalone USB Host also does the trick.


You can drive the RK-002 via our RK-004 when you set the MIDI port to ‘out mode’. Added bonus on the RK-004 is that you can update the firmware via an audio signal, e.g. people who use the RK-002 with the BeatStep Pro (which filters out our firmware SysEx messages) can now update their RK-002 via a plain and simple MP3 file.


Note that you can upload other firmware flavours to our RK-002 but here’s short summary of the Volca Sample firmware’s possibilities (v51+):

Here is a short overview of the RK-002 Play modes on the preloaded volca sample firmware:
By default there are two ‘hot areas’ on your keyboard:
C3-A3: 10 Sample triggers
Last triggered sample sets that specific sample under pitch control area at note C4 and up. You can change this behaviour via:


The ‘MIDI Program Change’ message can switch between RK-002/volca sample play modes:
Values can be :
0: singlechannel mode, chromatic area defined by last triggered channel note (like described above).
1..10: singlechannel mode, sample played in pitch control area defined by PC message nr 1..10

*as of firmware v50: Polyphonic play
11..19 : singlechannel / trigger area + polymux chromatic.
11..19 defines how many poly channels to use:
so let’s say you have 4 channels in the polyphonic group (Program Change=14), that means you have channel 1-4 are bundled as a 4-voice polyphonic sample player. The volca sample channel 5-10 are left for normal triggering via it’s sequencer for example, allowing you to play chords while you have a rhythm going on the internal sequencer.

*as of firmware v51: Multi timbral modes
Program change 20: multichannel mode / multi-timbral chromatic play
All 10  volca sample channels are mapped as original but with chromatic play added, NO trigger area.

21..29: multi-timbral chromatic+ trigger area
(The base channel is the RK-002 set global channel)
Example: RK002 MIDI global channel set to 1
mode: 21: all sample triggers on midi channel 1
chromatic play on volca channel 1 responding to midi channel 2

Example: RK002 MIDI global channel set to 4
mode 22: all sample triggers on midi channel 4
chromatic play on volca channel 1 responding to midi channel 5
chromatic play on volca channel 2 responding to midi channel 6

Note that the RK002 uses the available MIDI implementation of the volca Sample to make these extras possible. For example: it uses the part level, EG-control and pitch amount to emulate note velocity and a chromatic scale. The volca Sample’s pitch tuning however is not 100% chromatic and can deviate a bit at some notes.

as of version 58
Easy MIDI configuration! Start your synth and keep the key pressed on which you want to set the sample trigger basechannel. Plug the RK-002 and release the key within three seconds. Don’t press anything else or the RK-002 will not be reconfigured.

In order to do this, first the RK-002 must be unplugged/unpowered*.

  • Plug the RK-002 orange(MIDI out) end.
  • Set your keyboard/controller to the desired midi channel and octave you want to use with the RK-002.
  • Press the key on the keyboard/controller you want to set as basekey and keep it pressed.
  • Plug the RK-002 to the keyboard/controller.
  • Release the key on the keyboard/controller within three seconds.

After release, the midi channel and trigger basekey are set and saved to the RK-002 settings.

This configuration method applies for different firmware versions:

Firmware Action
Volca Sample set trigger basekey and midi channel
Modifier set midi channel
Arpeggiator set midi channel and command key

* Keep in mind that the RK-002 still runs a while on internal power after you have unplugged it. To drain the power from the RK-002, shorten the three middle pins on the black end with a piece of metal – the tip of a jack plug for example.

If you are using Google Chrome (or have the jazz-plugin enabled on other browsers which don’t support webMIDI) you can also reconfigure the RK-002 cable here:
If you want to change the firmware, the old updater is here (chrome preferred):

This updater is 1-way meaning you only have to connect the black end of the RK-002 to the MIDI OUT port of your MIDI Interface. The downside of this is that you are not actually seeing if the update has any effect. For that, use the 2-way connection (orange end of the RK-002 back into the MIDI-IN port of your interface) and go to the RK002/DUY Exchange Portal

Changing the MIDI response channel can be done without a computer, watch this video to see the startup procedure which allows you to change the basekey and MIDI channel. If you prefer a program like midi-ox (PC) or sysex librarian (MAC) to update (in case of sysex librarian; don’t forget to add a 150/200mS pause between sysex packages in the settings) you can download the firmware from the settings page mentioned above.
Note: The same which counts for normal usage of the cable: You need a MIDI-interface with midi power – and MIDI SystemExclusive message support – to do an update.

If the browser acts up with the plugin you can find a .zip file on the bottom of that page and some suggestions of PC/Mac software to upload the sysex file to the RK-002.

An extra note about MIDI power:
An easy test to see if the cable gets power is to feed the MIDI stream with a tempo/clock signal. The volca will start/stop with the tempo, indicating that the cable is working.

If you have no response whatsoever with the cable (and the volca does react to tempo with a normal MIDI cable) it probably means the midi sender you use does not have MIDI power.

A MIDI thru box (like our RK-004) can solve that, but you can also try and inject power to the RK-002 by using it via another synth or synth-module’s thru port like this:

MIDI sender -> [Synth in – Synth thru] -> RK-002 -> Volca