This is a modular analogue synthesiser and controller keyboard (actually a second modular synth in its own right) that was built from a design published in 1973 in the UK magazine Practical Electronics. This is the only one I have ever seen and is possibly the only surviving example.
The design was by G.D Shaw who later designed the Minisonic synthesiser. I think it is fair to say that the design was greatly influenced by the EMS Synthi in both functionality and controls (and sound I have heard). It was also the first magazine DIY synth published in the UK at least.
The Synthesiser is in two parts – a rack unit with the main sound modules (oscillators, amplifiers, tone filters, sample & hold, ring modulator, spring reverb, meter etc) and a separate controller keyboard with extra functionality (oscillator, VCF etc)
This example (the main rack unit) was built exactly to the published specification as far as I can tell and was completed to a very high standard (I would describe it as ‘laboratory grade’ construction). It features hand wired circuit boards (as per the published design and layouts) that plug in to a ‘backplane’ so it is a truly modular synth. All patching is done by 2mm plugs on the front panel, original patch cables are included.
The rack unit has a good range of modules included. Here is a complete list -
Stabilised Power Supply
2 x Input Amplifiers
2 x V.C. Modulators (Ramp & Pulse Generators)
2 x V.C. Oscillators (Triangle & Square Waves)
2 x Output Amplifiers
Reverberation Amplifier & Spring Line
2-Band Tone Filter
Envelope Shaper (Incl. Trapezoid)
Sample & Hold
Analogue Meter” Link