OnChip Systems

Most Curtis Electromusic Specialities or CEM ICs have part numbers of the form "33nn", and synth designers and techs often speak these part numbers without further attribution.

The company
Founded by Doug Curtis in 1979 specifically to design and manufacture integrated circuits for music synthesizers. Curtis Electromusic Specialties manufacturered a wide variety of ICs, many of which incorporated an entire synthesizer functional component, for example, the 3340, which contained a complete voltage controlled oscillator. By using chips from Curtis (and its competitor, SSM), synth manufacturers were able to considerably reduce the size of their circuitry. This (along with the advent of inexpensive microprocessor control) is what led to the wave of polyphonic analog synthesizers in the 1980s. By using the Curtis and SSM chips, manufacturers were able to shrink the size of their circuitry to where it could all fit in a package no larger than what was necessary to also house a keyboard and control panel.

Later developments included more highly integrated circuits such as the 3389 signal processor and the 3396 synth-on-a-chip. The further miniaturaization led to the creation of rackmount synthesizers, played via MIDI from a master keyboard, and saving performers both money and space. However, Doug Curtis folded his interest in CEM into OnChip Systems in 1988, and further design work on music synthesis products ended. Curtis himself largely moved out of the music field, occasionally doing consulting work with synth manufacturers until his untimely death in 2007.

Although the company still maintains a web page, it is no longer doing business. Before his death in 2007, Curtis apparently helped Dave Smith Instruments secure a supply of certain CEM chips to use in their Evolver line of synths. Whether these chips are new production or just stock that Curtis had warehoused is unclear.

CEM ICs

 * CEM3310 - Voltage Controlled Envelope Generator
 * CEM3320 - Voltage Controlled Filter
 * CEM3328 - Dual Voltage Controlled Amplifier
 * CEM3330 - Dual Voltage Controlled Amplifier
 * CEM3335 - Dual Voltage Controlled Amplifier
 * CEM3340 - Voltage Controlled Oscillator
 * CEM3345 - Voltage Controlled Oscillator
 * CEM3350 - Dual VC State Variable Filter
 * CEM3360 - Dual VCA
 * CEM3365 - Fast Dual DAC Multiplier
 * CEM3372 - uP Controllable Signal Processor
 * CEM3374 - Dual VCO
 * CEM3378 -
 * CEM3379 -
 * CEM3381 - Dual Low Rise VCA
 * CEM3382 - Dual Low Rise VCA
 * CEM3385 - Dual Low Noise V.C. Filter
 * CEM3387 - Low Noise V.C. Signal Processor
 * CEM3389 - Voltage Controlled Signal Processor
 * CEM3391 - uP Controllable Dynamic Signal Processor
 * CEM3394 -
 * CEM3396 - uP Controlled Waveshaper/Filter
 * CEM5310 - Hex ADSR and VCA
 * CEM5315 - Quant ADSR and Octave Divider
 * CEM5508 - Octal Sample & Hold
 * CEM5512 - Octal Double Buffered Sample and Hold
 * CEM5510 - Fast Octal Sample & Hold
 * CEM5530 - 30 Channel Sample & Hold
 * CEM5570 - Bus Controlled Signal Processor

CEM ICs used in

 * Akai AX-60 - 6 CEM3394
 * Akai AX-80 - 6 CEM3372
 * Bananna Poly Synth - 12 CEM3310, 12 CEM3340, 12 CEM3360
 * Böhm Soundlab - CEM3310, CEM3320, CEM3330, CEM3340
 * Buchla 296e - 1 CEM3360
 * Cheetah MS6 - 6 CEM3396
 * Crumar Bit 01 - 6 CEM3328 in late models
 * Crumar Spirit - 2 CEM3340, 2 CEM3350, 3 CEM3360
 * Crumar Trilogy - 6 CEM3310, 6 CEM3320, 6 CEM3330
 * Digisound 80-10 - 1 CEM3310
 * Digisound 80-16 - 1 CEM3350
 * Digisound 80-18 - 1 CEM3310
 * Digisound 80-19 - 1 CEM3360
 * Digisound 80-2 - 1 CEM3340
 * Digisound 80-21 - 1 CEM3340
 * Digisound 80-3 - 1 CEM3340
 * Digisound 80-4 - 3 CEM3330
 * Digisound 80-6 - 1 CEM3320
 * Digisound 80-7 - 1 CEM3320, 1 CEM3335
 * Digisound 80-9 - 1 CEM3330
 * Digisound 80-C9 - 2 CEM3310, 2 CEM3340, 1 CEM3360, 1 CEM3372
 * Digisound 80 Dev-91 - 1 CEM3391
 * Doepfer A-106-6 - CEM3379
 * Doepfer A107 - CEM3379
 * Doepfer A-109 - CEM3379
 * Doepfer A-111-1 - CEM3340
 * Doepfer A-111-2 - CEM3394?
 * Doepfer A-111-5 - CEM3394
 * Doepfer A121 - CEM3320
 * Doepfer A122 - CEM3320, CEM3379 in newer versions
 * Doepfer A123 - CEM3320
 * Doepfer A124 - CEM3379
 * Doepfer A-126 - CEM3382
 * Doepfer A-130 - CEM3381 in earlier models, alternately CEM3382
 * Doepfer A131 - CEM3381 in earlier models, alternately CEM3382
 * Doepfer A132-3 - CEM3360
 * Doepfer A-134 - CEM3381
 * Doepfer A179 - CEM3320
 * Doepfer Dark Energy - CEM3394
 * E&MM Spectrum - 2 CEM3310, 1 CEM3320, 2 CEM3330, 3 CEM3340
 * Elka Synthex - 8 CEM3320
 * Ensoniq ESQ1 - 1 CEM3360, 8 CEM3379
 * Ensoniq ESQ2 - 1 CEM3360
 * Ensoniq Mirage - 8 CEM3328
 * Ensoniq SQ-80 - 1 CEM3360, 8 CEM3379
 * Ensoniq SQ-81 - 1 CEM3360
 * Erik G's EH-30 Modular - 2 CEM3310, 4 CEM3330, 4 CEM3340
 * Fairlight CMI II - 8 CEM3320, in earlier versions
 * Fender/Rhodes Chroma - 8 CEM3350, 8 CEM3360
 * Fender/Rhodes Polaris - 6 CEM3372, 6 CEM3374
 * Keytek CTS-2000 - 8 CEM3389, 1 CEM5530
 * Linndrum - 2 CEM3320, 1 CEM3360
 * MIDIbox 3396 - CEM3396
 * Moog Memorymoog - 12 CEM3310, 19 CEM3340, 26 CEM3360
 * Oberheim DX - 3 CEM3328
 * Oberheim DMX - 1 CEM3320, or CEM3350 depending upon the voice card
 * Oberheim Martix 6 & 6R - 6 CEM3396
 * Oberheim Matrix 1000 - 6 CEM3396
 * Oberheim OB-1 - 2 CEM3310
 * Oberheim OB8 & OBX-A - 16 CEM3310, 16 CEM3320, 16 CEM3340, 2 CEM3360
 * Oberheim OB-SX - 2 CEM3310, 1 CEM3320, 2 CEM3340, 1 CEM3360
 * Oberheim Prommer - 1 CEM3328
 * Oberheim Xpander - 6 CEM3372, 6 CEM3374
 * Paia Proteus - 1 CEM3310, 1 CEM3320, 1 CEM3330, 2 CEM3340
 * Powertran Transcendent Polysynth - 2 CEM3310 per voice, 2 CEM3340 per voice
 * PPG Wave 2.0 - 4 CEM3310, 4 CEM3320
 * PPG Wave, 2.2 and 2.3 - 4 CEM3360
 * Rhodes Chroma - 8 CEM3350, 8 CEM3360 (some versions have 9)
 * Rhodes Polaris - 6 CEM3372, 6 CEM3374
 * Roland Jupiter 6 - 12 CEM3340, 6 CEM3360
 * Roland Jupiter 8/MKS-80 serial - 4 CEM3360
 * Roland Jupiter 8/MKS-80 to serial - 8 CEM3340, 4 CEM3360
 * Roland MKS-20 - 5 CEM3360
 * Roland Roland SH101 & MC202 - 1 CEM3340
 * Sequential Circuits Drumtraks - 2 CEM3320
 * Sequential Circuits Max - 6 CEM3394
 * Sequential Circuits Pro-1 - 2 CEM3310, 1 CEM3320, 3 CEM3340
 * Sequential Circuits Prophet 10 - 20 CEM3310, 10 CEM3320, 22 CEM3340
 * Sequential Circuits Prophet 2000 - CEM3379
 * Sequential Circuits Prophet 3000 - CEM3387
 * Sequential Circuits Prophet 5 Rev 3 - 10 CEM3310, 5 CEM3320, 11 CEM3340
 * Sequential Circuits Prophet 600 - 12 CEM3340, 4 CEM3360, 6 CEM3372
 * Sequential Circuits Six-Trax - CEM3372, 6 CEM3394
 * Sequential Circuits Split8 - 8 CEM3394
 * Sequential Circuits Studio 440 - 1 CEM3360, 8 CEM3389, 1 CEM5530
 * Sequential Circuits T8 - 16 CEM3340, 8 CEM3372
 * Sequential Circuits VS - 8 CEM3378, 8 CEM3382, 1 CEM5510, 1 CEM5530
 * Simmons Drums SDS8 - 5 CEM3372
 * Simmons Drums SDS800 - 2 CEM3394
 * Simmons Drums SDS9, SDS1000 - 3 CEM3394
 * Steiner EVI - CEM3340?
 * Synton Synrix - 2 CEM3310, 2 CEM3340, 2 CEM3350, 1 CEM3360
 * Thomas Henry: Deluxe VCO - CEM3340
 * Thomas Henry: A dual VCA - CEM3330
 * Waldorf Microwave1 revision A - 8 CEM3389
 * Waldorf Microwave1 revision B - 8 CEM3387
 * Waldorf Wave - 16 CEM3387

Data sheets
Data sheets are freely available from:
 * CEM3374.com
 * CEM3310, CEM3312, CEM3320, CEM3328, CEM3330, CEM3340, CEM3350, CEM3360, CEM3365, CEM3371, CEM3372, CEM3374, CEM3378, CEM3381, CEM3389, CEM3391, CEM3394, CEM3396, CEM5508, CEM5530