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

Tubbutec Polysex – dev blog


I thought I let you know what I’ve been doing since the last update. I worked a lot on my Polysix mod and will finally be able to sell it as a kit soon.


Tubbutec Polysex

What does the Polysex mod do?

There are some sound demos at the end of this article which should give you an impression, of some (but definitely not all) the new sounds which are achievable with this mod.

There are two different mods which can both be used at the same time:

  • The pitch mod routes the envelope to the pitch. You can choose the polarity of the envelope and the reference point in the envelope where the pitch is not changed. This mod is very useful to create portamento like effects, brass instruments, percussive sounds and much more.
  • The second mod is the voice spread mod which is a very powerful tool. You can determine the amount of voice spread, route the envelope and one of two LFOs to it and switch voice spreading on and off in poly mode. This mod can be used to adjust and modulate the fatness of the sound in unison mode, in poly mode you can modulate how detuned the Polysix sounds. This can lead to more natural sounds, but can also be used to accomplish complex sound effects.

What will the kit include?

The kit will include a PCB, all necessary parts and a front panel which you can use to mount the controls onto your Polysix. The front panel is made of fully anodized and printed aluminum and done in Polysix style (see images above and below). Instead of original Polysix knobs the kit will only contain similar ones, but it is possible to use Polysix knobs (one can find used ones). There will be a version with the PCB fully assembled and tested,too.


Prototype of the front panel made of plastic. I made this to check if everything fits as intended before having a large amount manufactured properly. The two switches on the right are not the final ones of course and as you can see I try a number of different knobs. The final version will be in Polysix style blue rather than grey.

Is it difficult to build?

No! The Polysex mod was designed as a kit, which means I tried to make it as easy as possible to assemble and install it. You will need basic soldering and metal work skills, but nothing you can’t learn by watching half an hour of a soldering tutorial on youtube. You will have to drill some holes into the metal casing of the Polysix, but precision is not needed because everything is covered by the front panel and will look very nice.

So why is it not already available? How long will it take? What are you doing the whole time?

At the moment I am working on collecting all the parts in larger quantities, getting the front panel and the PCBs produced, writing a manual and setting everything up nicely so you will get a good product and have a fun time 🙂

I have more questions!

Please don’t hesitate to ask them, I will answer and update this little FAQ.

Sound demos:

None of the sound examples make use of the effect section of the Polysix (or any external effects)


A simple arpeggio with mid attack and decay settings. The envelope to pitch amount is slowly increased to achieve a brass instrument like effect.


The whole Polysex mod is used in this example. A little bit of voice spread is set to achieve the sound of a slightly detuned synthesizer. Some more life is added by modulating the voice spread by the PWM LFO. Further more the envelope is routed to the pitch with the reference set to the sustain level and the polarity to negative, so that it pitches up as the sound decays.(The recording is a little bit distorted unfortunately)


Polysix in unison mode with the envelope routed to voice spread, long attack and release.
At first the reference is set to the sustain level, so the sound starts very dissonant, becomes more consonant and fat until it becomes a slowly phasing sound. As the key is released it reverses into dissonance.
The second time the reference is set to the zero level, the sound starts consonant, becomes dissonant and then consonant again.


An arpeggio in unsion mode. The voice spread amount is slowly increased – the sound becomes fatter and denser.


This sound demo uses voice spread modulated by the a fast PWM LFO.


Chords with long release and short attack, envelope routed to voice spread, with the sustain level as reference. As the chords decay, the sounds becomes more and more detuned. Sometimes the attack is set longer to achieve a sound that starts dissonant and increases in consonance.


The envelope is routed to the pitch to achieve a bass drum like percussive sound. The filter is modulated and different decay times and sustain levels are being set.

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.