The Crumar Bit One is an underrated but very capable 6-voice polysynth from the mid 1980s. It has a great sound, backed with Curtis filters, cool industrial design and a velocity sensitive keyboard – which can be assigned to the usual envelope intensity as well as rather more unusual things like the ADSR attack times, LFO speed and pulse width. Although it shipped with MIDI capability, it is very limited.
Instead of being a software modification to the synth, as is usually the case with these kinds of projects, the MIDI upgrade takes the form of a daughterboard that installs neatly inside the synth, with its own microcontroller to perform its functions. The synth's existing circuitry and software is left exactly as it was, the new hardware integrates around it.
The Bit One's tape mode has been repurposed to work also as a setup mode for the MIDI upgrade's extended features, which are controlled with notes on the keyboard - no drilling or case mods required!
The MIDI upgrade provides the following improvements to the synth :
- Local keyboard and external MIDI can be used at the same time - plugging a cable into the MIDI IN socket no longer disables the local keyboard. Local control can be turned off in setup mode if desired.
- Receiving channel for external MIDI can be set on the synth itself, and is remembered on power-off. (Transmitted MIDI channel is fixed on channel 1)
- MIDI handling is much more reliable. The board filters out all other channels before they get to the main CPU, also ignoring any messages that it cannot use, so there are no more MIDI overload-caused crashes, stuck notes etc.
- Now receives MIDI pitch bend (±2 semitone range) and mod wheel. MIDI mod wheel is provided by a dedicated LFO, independent from the Bit One's own two LFOs. The modulation depth can also be controlled by MIDI channel aftertouch.
- Receives MIDI sustain pedal (CC 64), which is used to control the Bit One's hold functionality.
- New for firmware v1.3 - includes an arpeggiator! Requires an external MIDI clock source such as a drum machine.
Note that the current version of the MIDI board's firmware is not compatible with the new Tauntek synth firmware, although I am working on resolving this.