MATRIXSYNTH: Crumar Bit One w/ MIDI Mod

Tuesday, November 02, 2021

Crumar Bit One w/ MIDI Mod

via this auction

Pics of the inside below.

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.

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.

Crumar Bit One with midi mod installed. It works great and has been serviced recently.

The keyboard contacts have been cleaned.
Potentiometers have been cleaned and lubricated. (Transmitted MIDI channel is fixed on channel 1)
All capacitor electrolytic are new.
The Rom Midi upgrade provides the following improvements to the synth :
Editing sounds via external controller: CC control of all sound parameters
Improved Sysex sound dump
More sensible settings on power-up: OMNI MIDI disabled (was enabled), Program Change enabled (was disabled), Sustain/Release via MIDI enabled (was disabled), MIDI mod CC enabled (was disabled), MIDI wheel message enabled (was disabled)
Previous MIDI channel retained on power-off
Partial real-time control (unfortunately, most parameters are only updated when a new note is triggered.
The PCB kit 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 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 v1.4 - includes an arpeggiator ! Requires an external MIDI clock source such as a drum machine."

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