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.

OnChip Systems
In 1988 with the advent of digital technology and software, Doug Curtis broadened his focus beyond synthesizers forming OnChip Systems and did no further design work on music synthesis products, except for occasional consulting for synth manufacturers until his premature death in 2007. Several more patents in his name are assigned for chips designed into various commercial products.

In 2016 OnChip Systems re-released the 3340, in response to Coolaudio's V3340 re-design of the part to the same specifications.

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

 * CEM 3310 – Voltage Controlled Envelope Generator
 * CEM 3320 – Voltage Controlled Filter
 * CEM 3328 – Dual Voltage Controlled Amplifier
 * CEM 3330 – Dual Voltage Controlled Amplifier
 * CEM 3335 – Dual Voltage Controlled Amplifier
 * CEM 3340 – Voltage Controlled Oscillator
 * CEM 3345 – Voltage Controlled Oscillator
 * CEM 3350 – Dual VC State Variable Filter
 * CEM 3360 – Dual VCA
 * CEM 3365 – Fast Dual DAC Multiplier
 * CEM 3372 - µP Controllable Signal Processor
 * CEM 3374 – Dual VCO
 * CEM 3378 – Voltage Controlled Signal Processor, (two-channel voltage controlled mixer, four-pole low-pass VCF, and VCA)
 * CEM 3379 – Voltage Controlled Signal Processor, (two-channel voltage controlled output pan, four-pole low-pass VCF, and VCA)
 * CEM 3381 – Dual Low Rise VCA
 * CEM 3382 – Dual Low Rise VCA
 * CEM 3385 – Dual Low Noise VCF
 * CEM 3387 – Low Noise voltage controlled Signal Processor
 * CEM 3389 – Voltage Controlled Signal Processor
 * CEM 3391 - µP Controllable Dynamic Signal Processor
 * CEM 3394 - µP Controllable synthesizer voice
 * CEM 3396 - µP Controlled Waveshaper/Filter
 * CEM 5310 – Hex ADSR and VCA
 * CEM 5315 – Quant ADSR and Octave Divider
 * CEM 5508 – Octal Sample & Hold
 * CEM 5512 – Octal Double Buffered Sample & Hold
 * CEM 5510 – Fast Octal Sample & Hold, custom-made for Sequential Circuits
 * CEM 5530 – 30 Channel Sample & Hold, custom-made for Sequential Circuits
 * CEM 5570 – Bus Controlled Signal Processor

Synthesizers using CEM ICs

 * Akai AX-60 – 6 CEM 3394
 * Akai VX600	- 6 CEM 3374B, 6 CEM 3378, 9 SSM 2300
 * Akai AX-80 – 6 CEM 3372
 * Böhm Soundlab – CEM 3310, CEM 3320, CEM 3330, CEM 3340
 * Buchla 296e – 1 CEM 3360
 * Cheetah MS6 – 6 CEM 3396
 * Crumar Bit 01 – 6 CEM 3328 in late models
 * Crumar Composer – 2 CEM 3310, 2 CEM 3320, 2 CEM 3330
 * Crumar Spirit – 2 CEM 3340, 2 CEM 3350, 3 CEM 3360
 * Stratus – 6 CEM3310, 6 CEM3320, 6 CEM3330
 * Crumar Trilogy – 6 CEM 3310, 6 CEM 3320, 6 CEM 3330
 * Deckard's Dream - 17 CEM3340
 * Digisound 80-10 – 1 CEM 3310
 * Digisound 80-16 – 1 CEM 3350
 * Digisound 80-18 – 1 CEM 3310
 * Digisound 80-19 – 1 CEM 3360
 * Digisound 80-2 – 1 CEM 3340
 * Digisound 80-21 – 1 CEM 3340
 * Digisound 80-3 – 1 CEM 3340
 * Digisound 80-4 – 3 CEM 3330
 * Digisound 80-6 – 1 CEM 3320
 * Digisound 80-7 – 1 CEM 3320, 1 CEM 3335
 * Digisound 80-9 – 1 CEM 3330
 * Digisound 80-C9 – 2 CEM 3310, 2 CEM 3340, 1 CEM 3360, 1 CEM 3372
 * Digisound 80 Dev-91 – 1 CEM 3391
 * Doepfer A-106-6 XP Filter - CEM 3379
 * Doepfer A-107 Multitype Morphing Filter - CEM 3379
 * Doepfer A-109 Voltage Controlled Signal Processor - CEM 3379
 * Doepfer A-111-1 High-End VCO - CEM 3340
 * Doepfer A-111-2 High End VCO II/VCLFO - CEM 3394?
 * Doepfer A-111-5 Synthesizer Voice - CEM 3394
 * Doepfer A-121 Multimode Filter - CEM 3320
 * Doepfer A-122 24dB Curtis Low Pass Filter - CEM 3320, CEM 3379 in newer versions
 * Doepfer A-123 24dB High Pass - CEM 3320
 * Doepfer A-124 Wasp Filter - CEM 3379
 * Doepfer A-126 Voltage Controlled Frequency Shifter - CEM 3382
 * Doepfer A-130 Voltage Controlled Amplifier - CEM 3381 in earlier models, alternately CEM 3382
 * Doepfer A-131 Voltage Controlled Amplifier - CEM 3381 in earlier models, alternately CEM 3382
 * Doepfer A-132-3 Dual linear/exponential VCA - CEM 3360
 * Doepfer A-134-1 Voltage Controlled Panner/Crossfader - CEM 3381
 * Doepfer A-179 Light Controlled Voltage Source - CEM 3320
 * Doepfer Dark Energy - CEM 3394 (original model)
 * E&MM Spectrum Synthesizer – 2 CEM 3310, 1 CEM 3320, 2 CEM 3330, 3 CEM 3340
 * EH-30 Modular – 2 CEM 3310, 4 CEM 3330, 4 CEM 3340
 * Elka Synthex – 8 CEM 3320
 * Elka EK-22 – 6 CEM3396
 * Ensoniq ESQ1 – 1 CEM 3360, 8 CEM 3379
 * Ensoniq ESQ2 – 1 CEM 3360
 * Ensoniq Mirage – 8 CEM 3328
 * Ensoniq SQ-80 – 1 CEM 3360, 8 CEM 3379
 * Ensoniq SQ-81 – 1 CEM 3360
 * Fairlight CMI II – 8 CEM 3320, in earlier versions
 * Fender/Rhodes Chroma – 8 CEM 3350, 8 CEM 3360
 * Fender/Rhodes Polaris – 6 CEM 3372, 6 CEM 3374
 * Forat F9000 – 4 CEM 3320
 * Hyperflange + Chorus by Craig Anderton - 1 CEM 3340
 * Hohner PK150 - 1 CEM 3391
 * Hohner PK250 - 2 CEM 3391
 * Keytek CTS-2000 – 8 CEM 3389, 1 CEM 5530
 * Kurzweil K250 – 8 CEM 3335
 * Linndrum – 2 CEM 3320, 1 CEM 3360
 * Linn 9000 – 4 CEM 3320
 * MIDIbox 3396 – CEM 3396
 * Moog Memorymoog – 12 CEM 3310, 19 CEM 3340, 26 CEM 3360
 * Mutronics Mutator
 * Oberheim DX – 3 CEM 3328
 * Oberheim DMX – 1 CEM 3320, or CEM 3350 depending upon the voice card
 * Oberheim Martix 6 & 6R – 6 CEM 3396
 * Oberheim Matrix 12 – 12 CEM 3374, 12 CEM 3372
 * Oberheim Matrix 1000 – 6 CEM 3396
 * Oberheim OB-1 – 2 CEM 3310
 * Oberheim OB-8 – 16 CEM 3310, 16 CEM 3320, 16 CEM 3340, 2 CEM 3360
 * Oberheim OB-SX – 2 CEM 3310, 1 CEM 3320, 2 CEM 3340, 1 CEM 3360 per voice
 * Oberheim OB-X – 2 CEM 3310
 * Oberheim OB-Xa – 16 CEM 3310, 8 CEM 3320, 16 CEM 3340, 2 CEM 3360
 * Oberheim Prommer – 1 CEM 3328
 * Oberheim Xpander – 6 CEM 3372, 6 CEM 3374
 * Octave Plateau Voyetra 8 – 16 CEM 3340
 * Octave The Cat SRM II – CEM 3340
 * Oberheim JLCooper filter mod – 1 CEM 3320 per voice
 * Paia Proteus – 1 CEM 3310, 1 CEM 3320, 1 CEM 3330, 2 CEM 3340
 * PAIA EKx-40 VCO - 1 CEM 3340
 * Powertran Transcendent Polysynth – 2 CEM 3310 per voice, 2 CEM 3340 per voice
 * PPG Wave 2.0 – 4 CEM 3310, 4 CEM 3320
 * PPG Wave, 2.2 and 2.3 – 4 CEM 3360
 * Rhodes Chroma – 8 CEM 3350, 8 CEM 3360 (some versions have 9)
 * Rhodes Polaris – 6 CEM 3372, 6 CEM 3374
 * Roland Jupiter 6 – 12 CEM 3340, 6 CEM 3360
 * Roland Jupiter 8/MKS-80 to serial #511799 (early models) – 8 CEM 3340, 4 CEM 3360
 * Roland Jupiter 8/MKS-80 serial #511800 up (later models) – 4 CEM 3360
 * Roland MKS-20 – 5 CEM 3360
 * Roland Roland MC202 – 1 CEM 3340
 * Roland Roland SH101 – 1 CEM 3340
 * Sequential Circuits Drumtraks – 2 CEM 3320
 * Sequential Circuits Max – 6 CEM 3394
 * Sequential Circuits Multi-Trak – 6 CEM 3394
 * Sequential Circuits Pro One – 2 CEM 3310, 1 CEM 3320, 3 CEM 3340
 * Sequential Circuits Prophet 10 – 20 CEM 3310, 10 CEM 3320, 22 CEM 3340
 * Sequential Circuits Prophet 2000 – 8 CEM 3379
 * Sequential Circuits Prophet 3000 – CEM 3387
 * Sequential Circuits Prophet 5 Rev 3 – 10 CEM 3310, 5 CEM 3320, 11 CEM 3340
 * Sequential Circuits Prophet 600 – 12 CEM 3340, 4 CEM 3360, 6 CEM 3372
 * Sequential Circuits Six-Trax – 6 CEM 3394
 * Sequential Circuits Split8 – 8 CEM 3394
 * Sequential Circuits Studio 440 – 1 CEM 3360, 8 CEM 3389, 1 CEM 5530
 * Sequential Circuits T8 – 16 CEM 3340, 8 CEM 3372
 * Sequential Circuits VS – 8 CEM 3378/3379, 4 CEM 3360, 2 CEM 3365, 4 CEM 5510, 2 CEM 5530
 * Simmons SDS7 – 1 CEM 3340 per module, 1 CEM 3372 per module
 * Simmons SDS8 – 5 CEM 3372
 * Simmons SDS800 – 4 CEM 3394
 * Simmons SDS9, SDS1000 – 3 CEM 3394
 * Solton Programmer 24 1 CEM 3350, 1 SSM 2044
 * Steiner EVI – CEM 3340?
 * Syntec Banana – 12 CEM 3310, 12 CEM 3340, 12 CEM 3360
 * Synton Synrix – 2 CEM 3310, 2 CEM 3340, 2 CEM 3350, 1 CEM 3360
 * Thomas Henry: Deluxe VCO – CEM 3340
 * Thomas Henry: A dual VCA – CEM 3330
 * Waldorf Microwave1 revision A – 8 CEM 3389
 * Waldorf Microwave1 revision B – 8 CEM 3387
 * Waldorf Wave – 16 CEM 3387

Data sheets
CEM 3310, CEM 3312, CEM 3320, CEM 3328, CEM 3330, CEM 3340, CEM 3350, CEM 3360, CEM 3365, CEM 3371, CEM 3372, CEM 3374, CEM 3378, CEM 3381, CEM 3389, CEM 3391, CEM 3394, CEM 3396, CEM 5508, CEM 5530 Some are also freely available from:
 * Curtis Electromusic
 * Synfo.nl