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

Insert jacks

I just put insert jacks on my ‘things to check first’ – list. A couple of days ago I repaired a Soundcraft mixer, after disassembling it and figuring out the signal path (didn’t have schematics) it turned out that the contacts on the insert jacks were corroded disabling the signal flow.

The very same problem just occurred in an audio amplifier whose headphone jacket had the same problem leading to a defect left channel.