Building a transistor organ monosynth

What’s the synth you’re working on?”, asked nobody at all after reading my post about PT2399 filters. Good question!

I’m a keyboard player. Piano originally, then organs (Hammond, Farfisa), then synths.

vintage Farfisa advert

I am mildly obsessed with transistor organs like the Farfisa Compact. Their circuits are ingenious but also simple enough for an untrained tinkerer like me to understand (just about). They were made over 50 years ago and they still work (just about). They are large and impressive examples of mid-century Italian design and their clever mechanisms let you fold them up into a box that you can take to a gig (just about).

Pocket Piano

I am also mildly obsessed with the Pocket Piano by Critter & Guitari. It is a tiny digital synth with charming wooden buttons that sounds unlike anything else I’ve ever played. It has several modes (I could write a book about the arpeggiator), but the one I insist on using on almost everything is RED (the one where the LED is red). It’s the basic polyphonic synth mode. It has four sounds, and one of them is a fizzy buzzsaw that cuts through any mix and spreads joy around the room. Combine it with the two-octave pitch bend knob and you have a dangerous weapon of joy.

The Farfisa multi-tone booster” sound and the Pocket Piano buzzsaw sound have a lot in common, and it’s the combination of these, along with a video about a quirky Soviet toy keyboard, that inspired me to start building a transistor organ monosynth back in July.

I’ll post more about the circuit and how it all works (and sounds!) another time. I’ve designed a PCB and ordered all the components so I’ll have something fun to show in a couple of weeks. It might be the keyboard of my dreams. Or an unusable monstrosity. Only time will tell!

January 3, 2023