Buy the RK-002

Popular uses

  • Add 1-channel sample triggers and chromatic 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…

Here's a video with Sonicstate’s Nick and Gaz having a ball with the RK-002 (mind you the RK-002 now is shipped with a new 3D-printed orange plug end as opposed to the version in the video. Also we have increased the length to 1.5m).

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:

  • Arpeggiator firmware
    Adds arpeggiator capabilities to your MIDI
  • KORG volca FM firmware (or Roland Boutiques)
    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.
  • KORG Kaossilator firmware
    This firmware allows you to play the KORG Kaossilator from 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 settings page. In this page it’s also possible to change the parameter mapping.


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-004 MIDI merger/splitter 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 chromatic play area at note C4 and up

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 chromatic area defined by PC message nr 1..10

*as of firmware v50:
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 volca sample channel 5-10 left for triggering

*as of firmware v51:
20 – multichannel mode / multi-timbral chromatic play – 10 midi channels, NO trigger area
21..29 multichannel mode / trigger area + multi-timbral chromatic

So; select 21 and you’ll have trigger and chromatic on the same channel, chromatic locked to volca sample channel 1

(The base channel is the RK-002 set global channel)
select 22, and you’ll have to trigger and +1 to chromatic
select 23, and you’ll have to trigger AND +1 to chromatic AND +2 to chromatic
etc, etc..

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, you can do that via this page (chrome preferred):

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

This entry was posted in RK002.