Playing around with the Minisonic II Analogue Synthesizer

Here I am making some initial knob twiddles and switch action on my Minisonic II. I recently improved the power supply, and tuning of the VCOs.

Category:

Music

Tags:

• Synthesizer
• Sound
• Minisonic
• Analog
• Analogue
• VCO
• VCF
• Synth

[DarkGlassly]

Nice to see it here - I made one myself at the time. Still have it buried away somewhere. It suffered from a few design flaws, but good to play around with and modify.

[cogshiftingman]

@DarkGlassly Thanks for the comment. If you decide to sell your original, please let me know - I'd like to have one as a comparison.

[DarkGlassly]

@cogshiftingman Think I'll be hanging onto it for a little longer. Your video has inspired me to dig it out and have a play, so I may do a demo video myself when I have time. I did make improvements to it, adding an ADSR generator, new pitch detector and switchable waveforms, but of course it still has some of the original problems such as drifting VCOs and slight pitch change induced by the ultrasonic key switching technique it used.

[cogshiftingman]

@DarkGlassly I look forward to the demo! I spent ages setting up the VCOs on mine. I was hampered by having to use a bonded transistor pair for one of them rather than the original dual transistor. The key switch/hold using HF is neat - I didn't have any problem with that part.

[timjmoran]

wow.. what a cool looking synth!! Is this a contemporary synth? Or vintage?

Made in the US? Looks kinda vintage to me....

[cogshiftingman]

@timjmoran Thanks - I made it myself: electronics are from a 1973 design. Cabinet design my own.

[janxenjanxen]

toys toys toys ;-)

[fritagogo1]

Ooops Electronic Wave Research with Mini Sonic ! 1973 ! Ok !

[thickinthead]

Thanks for putting this up. I also built one of these back in '74. The oscillators were temperature compensated by using stuck-together emitter coupled trannies (didn't the original use a crystal oven?), but mine still drifted wildly. The close tolerance resistor chain for the keyboard just wasn't close enough to make an even-tempered scale, and the ring modulator didn't modulate. Still, it taught me a lot about basic synths and was fun (bloody expensive fun!) to build.

[ricardlupus]

I started out building one of these, the original version from Practical Electronics magazine. Great starting point if you were on a tight budget, as I was as a young teenager. The original oscillators were completely uncompensated, so consequently drifted wildly with temperature. The Minisonic II was better, but I still had problems getting them to track properly. And I never got the envelope generators to work at all. Filter was nice, had a hint of organic Moog quality, being a ladder design.

[DarkGlassly]

@cogshiftingman The "pitch droop" was a variable problem, occurring when the key was released, I was never able to resolve it. Just seen your web site page about the Minisonic - excellent! I replaced most of the 741 ICs with LF351, which improved the sound quality with its much higher slew rate and lower noise. I did have the 128-note sequencer for the synth up until a few years ago, which I threw away.