Upcoming Tubbutec products

we’ve been working on a couple of projects recently and I thought I would give you some insight what we are working on.


Prototype of the Midisex retrofit


Midisex (a working title) is a retrofit for the Korg Polysix, that adds midi and additional features. It is very easy to install (just plug and play basically) and very compact.

Features amongst others are:

  • Midi in + Midi out
  • Sustain Pedal input
  • Additional play modes: 2Voice, 3 Voice, Polychord, extended unison mode
  • New arpeggiator / sequencer mode: Powerarp
  • All functions are easily accessible via buttons: suitable for live use
  • Midi channels and various other options can be configured without external tools
  • Midi controls arpeggiator, filter and more
  • Very easy to install, no soldering required (except for one solder joint if you want midi controlled filter)
  • High quality midi sockets and sustain pedal jack

Prototype of the Midisex retrofit

Some features explained

2 voice and 2 voice

While the original Polysix only features 6-voice polyphonic, unison and chord memory, this mod adds additional play modes.2-voice and 3-voice polyphonic modes are tradeoffs between the maximum fatness of the unison and the maximum number of voices of the polyphonic mode.


Polychord lets you assign a chord consisting of up to 6 notes to any key of the keyboard. This can be done very quickly and is very suitable for playing live. Of course you can combine this feature with the normal arpeggiator or the powerarp (see below). This makes it possible to have a sequenced chord progression in the matter of seconds.

extended unsion mode

The unison mode on the Polysix is basically a monophonic mode, but lacking almost all of the features  that most monophonic synths have.The extended unison mode this modification offers changes that.
– legato mode (no envelope retrigger when playing legato)
– key priority up / down / normal


Powerarp is a feature best described as a sequencer or a custom arpeggiator.
You can define a sequence of up to 64 notes (maybe more), that are then triggered by the arpeggiator clock. Up, down, updown and random are just a few ways to replay this sequence.  You can use this with all play modes including Chord and Polychord, which means you can define complex chord progressions and replay them using the arpeggiator, an external trigger or using midi.


The Midisex board is a direct replacement for the key assigner IC. It is only slightly larger then the original IC and can be replaced without soldering.

The Balancer

Most synthesizers, drum machines and effects only have an unbalanced -10dBV (consumer level) output. In a professional studio or live environment however a balanced connection with professional +4dBu level is desired. This eliminates ground loop induced noise as well as capacitive induced noise.

The Balancer (yes, a working title) is a little kit, that converts a -10dBV unbalanced audio signal to the professional +4dBu balanced signal.
It is meant to be built inside the equipment and is only sightly larger then an XLR or Jack connector. You can replace the existing connector, or add the Balancer to have both, unbalanced and balanced outputs.

The picture below shows a crude rendering of the XLR version.

imxlr (5)


  • unbalanced -10dBV to balanced +4dBu conversion
  • XLR and Jack version
  • Uses high quality Neutrik connectors
  • Very low noise design
  • DC output protection
  • Circuit built into connectors

Midified CR78 and TR606 sound demos

Here are two sound demos of a TR606 and a CR78 I midified.

Note the full velocity sensitivity capability of the 606 and the pseudo-velocity sensitivity of the CR78.



Some more infos about the CR78 mod:

Depending on the midi velocity sent to the device, the master volume is adjusted. That is of course not the same as full velocity sensitivity, but gives you a surprisingly great amount of flexibility. Think of the 808 for example which has one accent track – this is similar, but you can adjust the accent on the fly.

4x Midi CV Interface rev.2

While waiting for my Polysix mod PCB, I am working on rev. 2 of my midi to cv interface. Rev 1 was working well, but I realized I wanted some more features.


The new one will have:

  • 4 x CV out, 12 bit precision each
  • 4x Gate
  • Glide / portamento control for CV outs
  • For each CV you can switch glide mode between (on/auto/off)
  • For CV 3/4 you can choose individually whether they output midi notes or midi velocity from CV 1/2
  • Each CV can be controlled by midi notes and midi controller
  • FM in
  • Midi learn
  • Leds for gate and CV out
  • Doesn’t use smd parts an can be built by everyone

This basically enables you to have 4x polyphony with a modular synthesizer !…..and much more 🙂


Midi for Acetone Rythm Ace drum machines

we now offer to add midi input for Acetone Rythm Ace and similar drum machines.

contact us for details and prices.

An example: This is a Goya Melodic Rhythmer an analogue drum machine built into a guitar amplifier case. But is is not only very similar to the Acetone Rythm Ace, it also uses the same PCB ! So it is basically a RythmAce for cheap (but sounds the same).
The picture shows my own unit in my studio, it has been modified and now has midi input. Also the original lights at the front had been substituted by bright red LEDs. The downbeat indicator now blinks in sync with the midi clock.