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
After working for four years at Interdesign, Inc. Doug Curtis went on to found Curtis Electromusic Specialties in 1979. . He did this 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.

The designs
De-encapsulated (defective) CEM ICs are obviously bipolar arrays, although Interdesign or Ferranti die marks are missing. They exactly match the 1980 databook 201 Analog IC Designs from Interdesign.

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 - μP Controllable Signal Processor
 * CEM3374 - Dual VCO
 * CEM3378 - Voltage Controlled Signal Processor, (two-channel voltage controlled mixer, four-pole low-pass VCF, and VCA)
 * CEM3379 - Voltage Controlled Signal Processor, (two-channel voltage controlled output pan, four-pole low-pass VCF, and VCA)
 * CEM3381 - Dual Low Rise VCA
 * CEM3382 - Dual Low Rise VCA
 * CEM3385 - Dual Low Noise VCF
 * CEM3387 - Low Noise voltage controlled Signal Processor
 * CEM3389 - Voltage Controlled Signal Processor
 * CEM3391 - μP Controllable Dynamic Signal Processor
 * CEM3394 - μP Controllable synthesizer voice
 * CEM3396 - μP Controlled Waveshaper/Filter
 * CEM5310 - Hex ADSR and VCA
 * CEM5315 - Quant ADSR and Octave Divider
 * CEM5508 - Octal Sample & Hold
 * CEM5512 - Octal Double Buffered Sample & Hold
 * CEM5510 - Fast Octal Sample & Hold
 * CEM5530 - 30 Channel Sample & Hold
 * CEM5570 - Bus Controlled Signal Processor

Synthesizers using CEM ICs

 * Akai AX-60 - 6 CEM3394
 * Akai VX600	- 1 CEM3374B, 1 CEM3378, 9 SSM2300
 * Akai AX-80 - 6 CEM3372
 * Böhm Soundlab - CEM3310, CEM3320, CEM3330, CEM3340
 * Buchla 296e - 1 CEM3360
 * Cheetah MS6 - 6 CEM3396
 * Crumar Bit 01 - 6 CEM3328 in late models
 * Crumar Composer - 2 CEM3310, 2 CEM3320, 2 CEM3330
 * 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 A-107 - CEM3379
 * Doepfer A-109 - CEM3379
 * Doepfer A-111-1 - CEM3340
 * Doepfer A-111-2 - CEM3394?
 * Doepfer A-111-5 - CEM3394
 * Doepfer A-121 - CEM3320
 * Doepfer A-122 - CEM3320, CEM3379 in newer versions
 * Doepfer A-123 - CEM3320
 * Doepfer A-124 - CEM3379
 * Doepfer A-126 - CEM3382
 * Doepfer A-130 - CEM3381 in earlier models, alternately CEM3382
 * Doepfer A-131 - CEM3381 in earlier models, alternately CEM3382
 * Doepfer A-132-3 - CEM3360
 * Doepfer A-134 - CEM3381
 * Doepfer A-179 - CEM3320
 * Doepfer Dark Energy - CEM3394 (original model only)
 * E&MM Spectrum Synthesizer - 2 CEM3310, 1 CEM3320, 2 CEM3330, 3 CEM3340
 * EH-30 Modular - 2 CEM3310, 4 CEM3330, 4 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
 * Fairlight CMI II - 8 CEM3320, in earlier versions
 * Fender/Rhodes Chroma - 8 CEM3350, 8 CEM3360
 * Fender/Rhodes Polaris - 6 CEM3372, 6 CEM3374
 * Forat F9000 - 4 CEM3320
 * Keytek CTS-2000 - 8 CEM3389, 1 CEM5530
 * Kurzweil K250 - 8 CEM3335
 * Linndrum - 2 CEM3320, 1 CEM3360
 * Linn 9000 - 4 CEM3320
 * MIDIbox 3396 - CEM3396
 * Moog Memorymoog - 12 CEM3310, 19 CEM3340, 26 CEM3360
 * Mutronics Mutator
 * Oberheim DX - 3 CEM3328
 * Oberheim DMX - 1 CEM3320, or CEM3350 depending upon the voice card
 * Oberheim Martix 6 & 6R - 6 CEM3396
 * Oberheim Matrix 12 - 12 CEM3374, 12 CEM3372
 * Oberheim Matrix 1000 - 6 CEM3396
 * Oberheim OB-1 - 2 CEM3310
 * Oberheim OB-8 - 16 CEM3310, 16 CEM3320, 16 CEM3340, 2 CEM3360
 * Oberheim OB-SX - 2 CEM3310, 1 CEM3320, 2 CEM3340, 1 CEM3360 per voice
 * Oberheim OB-X - 2 CEM3310
 * Oberheim OB-Xa - 16 CEM3310, 8 CEM3320, 16 CEM3340, 2 CEM3360
 * Oberheim Prommer - 1 CEM3328
 * Oberheim Xpander - 6 CEM3372, 6 CEM3374
 * Oberheim JLCooper filter mod - 1 CEM3320 per voice
 * 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 Multi-Trak - 6 CEM3394
 * Sequential Circuits Pro One - 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 - 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 SDS7 - 1 CEM3340 per module, 1 CEM3372 per module
 * Simmons SDS8 - 5 CEM3372
 * Simmons SDS800 - 4 CEM3394
 * Simmons SDS9, SDS1000 - 3 CEM3394
 * Steiner EVI - CEM3340?
 * Syntec Banana - 12 CEM3310, 12 CEM3340, 12 CEM3360
 * 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