Electro harmonix Mini-Synthesizer (1980)
Model EH 0400

 

Basic monophonic synthesizer with a superb compact design and a membrane keyboard, similar concept found on EDP Wasp.

KEYBOARD portable 25 membrane keys with no velocity but the IMPACT SENSOR circuit which opens filter to major pressure.
Synth bottom is made out of cheap cardboard which is a total shame.
The EHX synth features 7 sliders potentiometers, 6 two-ways switches and a built-in audio speaker.

Back panel terminal connectors:
- audio signal output
- master tuning.

Power supply is a 9V external PSU or 2 x 9V batteries.

VOICE monophonic single analog oscillator structure.
A voice is composed by a 1 VCO pulse + 1 suboscillator (1 octave lower) which is obtained from divider structure, while octave function switches the VCO to 2 octaves below.

FILTER the VCF is resonant (Q switch) and the 2x switch steps the filters 1 octave up.

EFFECT VCF phase function activates a phase shifting on the sound.

 

ENVELOPE a single EG control on the cutoff filter: the START and STOP sliders set the lower and higher frequencies range at key down and up.

 

LFO a very basic modulation on the VCO pulse rectangular width (PWM).

MAINTENANCE after some pressures (and some years) the keyboard usually has some issues: it is necessary to refurbish the contacts using some homemade tricks or directly redisigning a new cardboard.

 

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AUDIO DEMO

filter test1 filter mode2 delay xperiment phasing on attack phasing on delay want to share some EHX minisynthesizer sounds? UPLOAD

 

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MINISYNTHESIZER MANUAL

APPROXIMATIVE SCHEMATICS

PATCH SHEET PRESETS

original brochure

M.Matthews

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