ARP2600 Analog Modular Synthesizer Replica

Overview The third analog synthesizer I built turned out to be a replica of the original ARP 2600 synthesizer - the idea evolved over time. I started out in the summer of 2007 with an empty set of 2 FracRac's, and the lessons from building the Pro-One modular which was 4U high and used high quality Spectrol pots. This was expensive design, and the 1/8" shaft Spectrols were of variable quality, I had to replace quite a few pots after burning in the sysetm - not a happy badger! For my third modular I decided to use cheaper Alpha pots with splined shafts and low cost mixer style plastic knobs (15p rather than £1.00+). This reduced the cost of building a module, albeit its a compact panel layout.

Initially I started building a collection of filter modules; various ARP designs, SSM2040 and CEM3320, and then some modern VCA's using the SSM2018 and SSM2164 chips. In 2008 I started tackling the ARP 4027-1 VCO, and over a number of months perfected the design. By late 2008 the idea of a FracRac 2600 was becoming a reality, especially once Tony at Oakley Sound Systems announced PCB's for the 4014 and 4019. I have built so many filters and other modules, that I'll need to build a second cabinet with 2 FracRacs to hold everything.

Design Details Confident that I could at least find the necessary electronics, I could now plan the physical format. The original physical design was based on high quality electronics and mechanics, and I set the same objectives albeit with some compromises and changes:

• The mdodules are all standard 3U 3" wide FracRac.
• The panels are PCB material spray painted with car aryclic paint and then lettered with Transmat.
• 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
• Minature "round" toggle switches.
• Lights - 3mm LED's mounted in round plastic LED holders(Clip Lites).
• The power supply is 1.5A +/-15V and the transformer is remote.
• A BBD (MN3007) Digital Reverb replaces the original spring reverb.