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Retrokits RK-006

Portable USB MIDI/Gate Hub By Simon Sherbourne
Published March 2022

Retrokits RK-006

Retrokits’ RK‑006 is a tiny but incredibly versatile hub for MIDI, USB and modular.

Retrokits’ RK‑005 (reviewed in SOS March 2019) was the right product at the right time, arriving just as I was getting into tabletop synth jams. It allowed my Circuit, OP‑1 and Pocket Operators to talk to each other, without needing a computer or iPad to coordinate things. The 006 is an even more capable hub that’s perfect for my expanded synth shelf, which now revolves around a Maschine+, and which I like to use both standalone and with a DAW. The RK‑006 features 10 MIDI outputs and two inputs as well as USB hosting and analogue clocking and gating, while still being small enough to slip into a Swan Vesta box.

Split Personality

The RK‑006 wears multiple hats, facilitated by on‑board config presets and a web‑based setup tool. Connected to your computer or tablet it’s a straightforward 2‑in/10‑out MIDI interface. It also works in this mode with some standalone workstations: I used it for a while connected to an MPC Live II, and it now spends much of its time as a MIDI interface for my standalone Maschine+.

When not connected to a host the RK‑006 becomes a giant USB‑powered MIDI thru box, merging its two inputs and passing them to all 10 outs if you like (you can also split the two inputs to merge to odd and even outputs). This alone would be super‑useful in a live or DAW‑less setups, but like the 005, the 006 can also host USB MIDI devices. This means you can interconnect MIDI modules and controllers via a USB hub, and get more input sources.

Jack Of All Trades

Traditionally a MIDI interface with this level of connectivity would be a 19‑inch rack unit. The 3.5mm jack ports used on the RK‑006 allow for its sub‑credit‑card footprint. The ports use the now standard TRS‑A connections, meaning you can replace MIDI cables with stereo mini‑jack cables to connect to other devices that use this format. Of course full‑sized MIDI DIN connectors are still everywhere, so the RK‑006 comes with an adaptor. For an entirely reasonable €8 you can add the cable bundle, which provides four more DIN break‑outs and a TRS‑A to TRS-B cable for direct connection to non‑conformists like the original Novation Circuit.

The RK‑006 has many more possibilities and tricks up its sleeve than I’ve made use of, but it’s become an essential part of my rig...

The use of jack ports has other interesting possibilities, which Retrokits have taken full advantage of. Outputs can be repurposed as analogue gate/trigger sources. You can output analogue clock in any format I can think of, with timing taken from incoming MIDI Clock or the RK‑006’s own internal tempo. The clock, or run/stop triggers, can be tied to MIDI Start/Stop messages. You can even adjust timing.

MIDI notes can also be used to trigger gate pulses. You could use this as another way to clock a modular synth (with swing if you wanted), or by triggering different ports from different MIDI notes you could sequence drum modules via the RK‑006. In fact you could use an RK‑006 to interface a MIDI pad controller with your modular without a computer. Assign some ports as gates, another as a Start/Stop, another as a Reset, etc.

RK-006 Conclusion

The RK‑006 has many more possibilities and tricks up its sleeve than I’ve made use of, but it’s become an essential part of my rig whether I’m running with or without a computer.


Incredibly versatile hub for MIDI, USB and modular, and probably the only MIDI interface you’ll ever need in or out of the studio.


£149 including VAT.

€134.71 euros