The MiMi-a

The MiMi-a Polyphonic Synthesizer
The MiMi-a is a microprocessor controlled six-voice multitimbral analog MIDI synthesizer that I built (mostly) during the spring of 1987. That makes it ... wow ... over 30 years ago ...

Each voice is mostly analog; all signal processing is analog, with the envelope generators and LFO's being partly digital, as well as the oscillator front-ends. This makes for a warm analog sound while at the same time retaining digital precision for the envelope and LFO timing, and oscillator frequencies.

Each voice consists of:

Two oscillators, A and B, each with an adjustable range of six octaves, with sawtooth, pulse and square waveforms, as well as combinations of these, as well as two ring-modulator-type waveforms. Oscillator A can be hard-synced to oscillator B.
A combined sub-oscillator/noise generator (oscillator C).
A Moog-type -24dB/octave voltage controlled lowpass filter with voltage controlled resonance.
A linear/exponential VCA.
Three ADSSR envelope generators, one for the filter, one for the VCA and one assignable.
One syncable LFO.

The LFO and General Contour Generator are individually assignable to the following destinations:

Oscillator A pitch, or oscillators A+B pitch
Oscillator A, B or A+B waveshape
Filter (LFO only, the filter has its own envelope)
Filter-modulation-by-oscillator-B amount (Envelope only)
Filter peak (resonance)

As well as the programmable level control, the LFO is also routed through the modulation wheel in parallel. A bend wheel can be routed to oscillator A or oscillators A+B, with a range of up to one octave up or down.

There are six individual outputs which may be routed to the any of the six voices. A number of key assign modes are available, as well as a sostenuto function, whereby only keys depressed are affected by the sustain pedal. A multitimbral mode (VGC mode - short for Voice Group Configuration) is also available, although for ease of use two-way split and layer modes are also directly available.

The MiMi-a is powered by a Z80B microprocessor, running overspeed at 8 MHz. Apart from play and edit modes, there's also a machine language monitor, and it's possible to download application software via MIDI. For instance, I once ported John Simonton's Pink Tunes to the MiMi-a.

The instrument is built in a Yamaha CP-10 case, with only the bottom and sides and keyboard having been kept from the original. After quite a few years in service, the original carbon-on-rubber keyboard switches started acting erratically, and were replaced by keyboard switches from a scrapped computer terminal keyboard. The name MiMi-a is an acronym for Microprocessor-controlled Musical Instrument, version a.

Check here for a closer look inside the case.

For an example of what it sounds like, check out my music page.

The MiMi-a from the back

Back to my synth page.