Roland 100M Analog Modular Synthesizer Replica

Overview The fourth modular analog synthesizer I have built is a replica of the Roland 100M - the project toke 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. I was also in the process of building the SH-5 Filter Cube, which needed a home....The Roland 100M has a strong reputation for its flexibility and excellent sounds, so the project was "approved". The aim is 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 so successful in the ARP 2600 clone. Once again it uses cheap but high quality Alpha pots with splined shafts and low cost mixer style plastic knobs. Front panels were immediately made in aluminium, rather than my usual interim painted PCB versions.

Design Details Similar specifications to the ARP2600 FracRac:

• The modules are all standard 3U 3" wide FracRac.
• The panels are Aluminium
• Blacet Research FracRac rails are used.
• The +/-15V power supply is Oakley Sound with Oakly Dizzy.
• The Midi to CV/Gate interface is from MIDIBOX with a 16x2 LCD
• Pots are Alpha 16mm, cheap but reliable
• Slide switches usually mounted directly to the PCB's.
• Lights - 3mm LED's mounted in round plastic LED holders(Clip Lites).
• The power supply is 1.5A +/-15V and the transformer is remote.