Roland 100M


Overview The fourth modular analog synthesizer I built was a replica of the Roland 100M – the project took hold very quickly after I bought some BA6110 VCA chips in 2008 and realised I could build the VCF, VCA and LFO. Then I looked at the VCO schematic and realised it was an excellent design that could be modified to remove the uA726 heated transistor pair. The Roland 100M has a strong reputation for its flexibility and excellent sounds, so the project was “approved”. The aim was to complete the synth within 6 months, a world record for me! I started out in the spring of 2009, with the PCB designs completed by June, and a FracRac frame arriving soon after. The synthesizer uses the same 3U FracRac design that proved successful in the ARP 2600 clone and there are a total of 10 modules.

Design Details

  • The modules are all standard 3U 3” wide FracRac.
  • The panels are 2mm aluminium panels.
  • Blacet Research FracRac rails.
  • +/-15V power supply is Oakley Sound with Oakley Dizzy.
  • Midi to CV/Gate interface is Oakley Sound.
  • Alpha 16mm pots, cheap but reliable.
  • 15mm Mixer style plastic knobs.
  • Slide switches usually mounted directly to the PCB’s.
  • 3mm LED’s mounted in round plastic LED holders(Clip Lites).

Modules – Top Row

  • Oakley Sound – MIDI/CV
  • AM8125 VCO (x3)
  • AM8110 VCA

Modules – Bottom Row

  • AM8152 Noise, S&H and Lag
  • AM8150 LFO & Gate Delay
  • AM8121 4-pole LPF and 1-pole HPF
  • AM8075 ARP 24dB VCF
  • AM8140 Dual ADSR

Design Changes & Outcome  The synthesizer has proved the core of my setup and used to test production modules over the last 10 years. The panels were all replaced with professionally produced versions in 2011 and jack sockets upgraded. A third VCO was added and a few non 100M modules removed, such as the AM8106 Juno 106 VCF. The AM2140 was also culled to release the SSM2020 for a customer. A second 100M clone synthesizer with the same module configuration was also produced and finally completed in 2018, along with the addition of a Roland 181 Keyboard.

Copyright AMSynths 2017