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MIDI Ultimate Synth

The MIDI Ultimate project is a fully-featured analogue synth with a performance comparable to many commercially available instruments. The MIDI Ultimate is an evolution of the (MFOS) Sound Lab Ultimate design by the late Ray Wilson who is credited for much of the design which has been reproduced with kind permission of in the US.

This project will appeal to both those whose primary interest is in electronics and those whose interest is purely making music. This is quite a large build to take on with nearly 700 components (fig 1) and may initially be seen as rather daunting. However, the construction is covered in 6 issues of the EPE magazine with cover dates from February 2019 to July 2019. With care and with our detailed constructional articles, it is quite achievable. The two essential skills needed to undertake this construction are soldering and component identification. If these are new to you then numerous guides and videos can be found online. If you are a first timer or relatively inexperienced in electronics, practice your soldering before starting on this synth. Whilst the component count is high, the PCB is assembled systematically with each individual section tested before moving onto the next.

Synth Features

  • Three Musically Accurate Voltage Controller Oscillators (VCOs) with sawtooth and variable width pulse wave forms, pulse width modulation, hard-sync, log CV inputs.
  • Voltage Controlled Low Pass Filter (VCF) 12db/Oct doubles as a sine wave oscillator
  • Voltage Controlled Amplifier (VCA)with log response
  • White Noise Generator
  • Active 8 Channel Mixer for all VCO waveforms, noise and external input
  • Two Attack, Decay, Sustain & Release Envelope Generators (ADSR)
  • Two Low Frequency Oscillators (LFO) with square, ramp, triangle and sawtooth waveforms
  • Repeat Gate Generator that can also double as another square wave LFO)
  • Sample & Hold (S&H) with variable sample rate and glide
  • Toggle Switch Patching with potentiometer mixing
  • Echo Effect Sound Processor
  • MIDI to CV Interface with 1-16 channel selector switch, responds to all 128 MIDI note keys
  • Headphones and Line output
  • Integral +/- 12Vdc Power supply Regulator (needs external 12Vac 500mA plug top adaptor)
  • DIY Construction with through hole components
  • Single board design with PCB mounted pots and switches eliminates panel wiring


Block Diagram with Patching (click on image for full size view)

Soundtronics MIDI Ultimate Block Diagram

Consistent with our philosophy, you can choose whether to purchase individual components, kits, panels, case etc. To help you make your decision, the following is a complete product list if purchasing everything from Soundtronics. For a complete kit of parts, see here.

PCBs Kits Enclosures / Panels Miscellaneous
Main 7215-074 Fixings 7215-170 Hardwood Case 7250-015 UK Mains Adaptor 1090-080
PSU PCB 7215-083 VCOs 7215-268 PSU Case 7215-383 Set of Coloured Knobs
Jack Socket PCB 7210-736 VCF 7215-269 Front Panel 7215-574 Set of Black Anodised Knobs
MIDI Socket PCB 7210-790 Mixer 7215-270 Back Panel 7215-874 Pack of 7 Jack Sockets 7212-207
  VCA 7215-271 Acrylic Back Panel* 7215-384 Stereo Jack Socket 7212-201
  Echo 7215-272 Rear Panel 7215-385 MIDI Sockets 7212-318 x 2
  Noise 7215-273    
  Amplifier 7215-274    
  LFOs 7215-275    
  ADSRs 7215-276    
  S&H 7215-277    
  Gate 7215-278    
  MIDI I/F 7215-279    
  PSU 7215-283    

*Optional if not purchasing the aluminium back panel 7215-874