# OnChip Systems

**OnChip Systems** formerly known as **Curtis Electromusic Specialities**.

## The company

After working for four years at Interdesign, Inc. Doug Curtis went on to found Curtis Electromusic Specialties in 1979.^{[1]} 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 CEM3340, 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.^{[2]}

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.^{[2]}^{[3]}

## 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.^{[2]}^{[4]}^{[5]}

In 2016 OnChip Systems re-released the 3340, in response to Coolaudio's V3340 re-design of the part to the same specifications.^{[6]}^{[7]}

## Clones

Alfa Rpar AS produces the AS33xx equivalent ICs in DIP and SMT packages.

## The designs

CEM ICs have part numbers of the form "33nn", and synth designers and techs often speak these part numbers without further attribution.^{[2]} 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.^{[1]}

## CEM ICs

- CEM3310 – Voltage controlled envelope generator (VCEG)
- CEM3320 – Voltage controlled filter (VCF)
- CEM3328 – Four pole low pass VCF
- CEM3330 – Dual voltage controlled amplifier (VCA)
- CEM3335 – Dual VCA
- CEM3340 – Voltage controlled oscillator (VCO)
- CEM3345 – VCO
- CEM3350 – Dual VC state variable filter (VCSVF)
- 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 / PDA381 – Dual low rise VCA
- CEM3382 / PDA382 – 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 / PD508 – Octal sample & hold
- CEM5512 – Octal double buffered sample & hold
- CEM5510 – Fast octal sample & hold, custom-made for sequential Circuits
- CEM5530 – 30 channel sample & hold, custom-made for sequential Circuits
- CEM5570 – Bus controlled signal processor

^{[8]}^{[9]}^{[10]}^{[11]}

## Synthesizers using CEM ICs

### Prebuilt

- Akai AX-60 – 6 x CEM3394
- Akai AX-80 – 6 x CEM3372
- Akai VX600 - 12 x CEM3374B, 12 x CEM3378
- Behringer Crave - 1 x CEM3340
- Behringer Neutron - 2 x CEM3340
- Buchla 296e – 1 x CEM3360
- Cheetah MS6 – 6 x CEM3396
- Crumar Bit 99 – 6 x CEM3328
- Crumar Bit One – 6 x CEM3328 in late models
- Crumar Composer – 2 x CEM3310, 2 x CEM3320, 2 x CEM3330
- Crumar Spirit – 2 x CEM3340, 2 x CEM3350, 3 x CEM3360
- Crumar Stratus – 6 x CEM3310, 6 x CEM3320, 6 x CEM3330
- Crumar Trilogy – 6 x CEM3310, 6 x CEM3320, 6 x CEM3330
- Doepfer A-106-6 XP Filter - CEM3379
- Doepfer A-107 Multitype Morphing Filter - CEM3379
- Doepfer A-109 Voltage Controlled Signal Processor - CEM3379
- Doepfer A-111-1 High-End VCO - CEM3340
- Doepfer A-111-2 High End VCO II/VCLFO - CEM3340
- Doepfer A-111-3 Micro Precision VCO - CEM3340
- Doepfer A-111-4 Quad Precision VCO - CEM3340
- Doepfer A-111-5 Synthesizer Voice - CEM3394
- Doepfer A-121 Multimode Filter - CEM3320
- Doepfer A-122 24dB Curtis Low Pass Filter - CEM3320, CEM3379 in later versions
- Doepfer A-123 24dB High Pass - CEM3320
- Doepfer A-124 Wasp Filter - CEM3379
- Doepfer A-126 Voltage Controlled Frequency Shifter - CEM3382
- Doepfer A-130 Voltage Controlled Amplifier - CEM3381 in earlier models, alternately CEM3382
- Doepfer A-131 Voltage Controlled Amplifier - CEM3381 in earlier models, alternately CEM3382
- Doepfer A-132-3 Dual linear/exponential VCA - CEM3360 (early versions)
- Doepfer A-134-1 Voltage Controlled Panner/Crossfader - CEM3381
- Doepfer A-179 Light Controlled Voltage Source - CEM3320
- Doepfer Dark Energy - CEM3394 (original model)
- Dynacord Add-one - 8 x CEM3389
- EH-30 Modular – 2 x CEM3310, 4 x CEM3330, 4 x CEM3340
- Elka Synthex – 8 x CEM3320
- Elka EK-22 – 6 x CEM3396
- Ensoniq ESQ-1 – 1 x CEM3360, 8 x CEM3379
- Ensoniq ESQ-2 – 1 x CEM3360
- Ensoniq Mirage – 8 x CEM3328
- Ensoniq SDP-1 - 10 x CEM3328
- Ensoniq SQ-80 – 1 x CEM3360, 8 x CEM3379
- Ensoniq SQ-81 – 1 x CEM3360
- Fairlight CMI II – 8 x CEM3320, in earlier versions
- Fender/Rhodes Chroma – 8 x CEM3350, 8 x CEM3360
- Fender/Rhodes Polaris – 6 x CEM3372, 6 x CEM3374
- Forat F9000 – 4 x CEM3320
- Hyperflange + Chorus by Craig Anderton - 1 x CEM3340
- Hohner PK150 - 1 x CEM3391
- Hohner PK250 - 2 x CEM3391
- Keytek CTS-2000 – 8 x CEM3389, 1 x CEM5530
- Kurzweil K250 – 8 x CEM3335
- Linndrum – 2 x CEM3320, 1 x CEM3360
- Linn 9000 – 4 x CEM3320
- Marion Systems MSR-2 - CEM3397
- Marion Systems MS9C - 8 3387
- Moog Memorymoog – 12 x CEM3310, 19 x CEM3340, 26 x CEM3360
- Mutronics Mutator
- Oberheim DX – 3 x CEM3320
- Oberheim DMX – 1 x CEM3320, or CEM3350 depending upon the voice card
- Oberheim Matrix 6 & 6R – 6 x CEM3396
- Oberheim Matrix 12 – 12 x CEM3374, 12 x CEM3372
- Oberheim Matrix 1000 – 6 x CEM3396
- Oberheim OB-1 – 2 x CEM3310
- Oberheim OB-8 – 16 x CEM3310, 16 x CEM3320, 16 x CEM3340, 2 x CEM3360
- Oberheim OB-SX – 2 x CEM3310, 1 x CEM3320, 2 x CEM3340, 1 x CEM3360 per voice
- Oberheim OB-X – 2 x CEM3310
- Oberheim OB-Xa – 16 x CEM3310, 8 x CEM3320, 16 x CEM3340, 2 x CEM3360
- Oberheim Prommer – 1 x CEM3328
- Oberheim Xpander – 6 x CEM3372, 6 x CEM3374
- Octave Plateau Voyetra 8 – 16 x CEM3340
- Octave The Cat SRM II – CEM3340
- JLCooper Oberheim filter mod – per voice: 1 x CEM3320
- Polyfusion Series 2000 Synthesizer - 3340 revision D only, revision A and B are based on the μA726 and XR2207
- PPG Wave 2.0 – 4 x CEM3310, 4 x CEM3320
- PPG Wave, 2.2 and 2.3 – 4 x CEM3360
- Rhodes Chroma – 8 x CEM3350, 8 x CEM3360 (some versions have 9)
- Rhodes Polaris – 6 x CEM3372, 6 x CEM3374
- Roland Jupiter 6 – 12 x CEM3340, 6 x CEM3360
- Roland Jupiter 8/MKS-80 to serial #511799 (early models) – 8 x CEM3340, 4 x CEM3360
- Roland Jupiter 8/MKS-80 serial #511800 up (later models) – 4 x CEM3360
- Roland MKS-20 – 5 x CEM3360
- Roland Roland MC202 – 1 x CEM3340
- Roland Roland SH101 – 1 x CEM3340
- Sequential Circuits Drumtraks – 2 x CEM3320
- Sequential Circuits Max – 6 x CEM3394
- Sequential Circuits Multi-Trak – 6 x CEM3394
- Sequential Circuits Pro One – 2 x CEM3310, 1 x CEM3320, 3 x CEM3340
- Sequential Circuits Prophet 10 – 20 x CEM3310, 10 x CEM3320, 22 x CEM3340
- Sequential Circuits Prophet 2000 – 8 x CEM3379
- Sequential Circuits Prophet 3000 – CEM3387
- Sequential Circuits Model 206 – 6 x CEM3394 (sound card for the Sente SAC-1.
^{[12]}) - Sequential Circuits Prophet-5, Rev 3 – 10 CEM3310, 5 x CEM3320, 11 x CEM3340
- Sequential Circuits Prophet 600 – 12 x CEM3340, 4 x CEM3360, 6 x CEM3372
- Sequential Circuits Six-Trax – 6 x CEM3394
- Sequential Circuits Split8 – 8 x CEM3394
- Sequential Circuits Studio 440 – 1 x CEM3360, 8 x CEM3389, 1 x CEM5530
- Sequential Circuits T8 – 16 x CEM3340, 8 x CEM3372
- Sequential Circuits VS – 8 x CEM3378/3379, 4 x CEM3360, 2 x CEM3365, 4 x CEM5510, 2 x CEM5530
- Simmons SDS1000 – 3 x CEM3394
- Simmons SDS200 - 2 x CEM3394
- Simmons SDS400 - 4 x CEM3394
- Simmons SDS7 – – per module: 1 x CEM3340, 1 x CEM3372
- Simmons SDS8 – 5 x CEM3372
- Simmons SDS800 – 4 x CEM3394
- Simmons SDS9 – 1 x CEM3372, 3 x CEM3394
- Solton Programmer 24 - 1 x CEM3350
- Solton TS3 - 3 x CEM3360
- Solton TS4 - 1 x CEM3360
- Steiner EVI – 1 x CEM3340, 1 SSM2040
- Syntec Banana – 12 x CEM3310, 12 x CEM3340, 12 x CEM3360
- Synton Synrix – 2 x CEM3310, 2 x CEM3340, 2 x CEM3350, 1 x CEM3360
- Voyetra 8 - 16 x CEM3340
- Waldorf Microwave1 revision A – 8 x CEM3389
- Waldorf Microwave1 revision B – 8 x CEM3387
- Waldorf Wave – 16 x CEM3387

### DIY projects

- Böhm Soundlab – CEM3310, CEM3320, CEM3330, CEM3340
- Deckard's Dream - 17 x CEM3340
- Digisound 80-10 – 1 x CEM3310
- Digisound 80-16 – 1 x CEM3350
- Digisound 80-18 – 1 x CEM3310
- Digisound 80-19 – 1 x CEM3360
- Digisound 80-2 – 1 x CEM3340
- Digisound 80-21 – 1 x CEM3340
- Digisound 80-3 – 1 x CEM3340
- Digisound 80-4 – 3 x CEM3330
- Digisound 80-6 – 1 x CEM3320
- Digisound 80-7A – 1 x CEM3320, 1 x CEM3335
- Digisound 80-9 – 1 x CEM3330
- Digisound 80-C9 – 2 x CEM3310, 2 x CEM3340, 1 x CEM3360, 1 x CEM3372
- Digisound 80 Dev-91 – 1 x CEM3391
- Dusk work Self-Tuning VCO - 1 x AS3340
- E&MM Spectrum Synthesizer – 2 x CEM3310, 1 x CEM3320, 2 x CEM3330, 2 x CEM3340
- Elektor new synthesiser - 2 x CEM3310, 1 x CEM3320, 2 x CEM3340
- Elektor polyphonic synthesiser - per voice: 2 x CEM3310, 1 x CEM3320, 1 or 2 x CEM3340
- HBO AS3394 Synthesizer - 1 x CEM3394 per voice (up to six voices)
- Juergen Haible Dual VCO - 2 x CEM3340
- Kijimi - 16 x AS3340, 24 x CEM3360
- MIDIbox 3396 – CEM3396
- PAiA 6750 Hyperflange & Chorus, 1 x CEM3340
- PAiA Proteus 1 – 1 x CEM3310, 1 x CEM3320, 1 x CEM3330, 2 x CEM3340
- PAIA EKx-40 VCO - 1 x CEM3340
- Powertran Transcendent polysynth - per voice: 2 x CEM3310, 2 x CEM3340
- Thomas Henry Deluxe VCO – CEM3340
^{[13]} - Thomas Henry: A dual VCA – CEM3330
^{[13]}

^{[9]}^{[14]}^{[15]}^{[16]}^{[17]}^{[18]}^{[19]}

## See also

## References

- ^
^{a}^{b}Pictures of dead CEM chips at Stromeko Synth World - ^
^{a}^{b}^{c}^{d}Curtis Electromusic, Electronic Music wiki - ^ About the Company, Curtis Electromusic
- ^ Doug Curtis, Curtis Electromusic
- ^ About the Company, Curtis Electromusic
- ^ Curtis Electromusic Specialties, Facebook, 5 June 2016
- ^ Curtis Family Speaks Out Against Behringer Synth Clone Plans Using CEM3340 by Rounik Sethi, Ask.Audio, 21 Mar 2017
- ^ CEM data sheets
- ^
^{a}^{b}Various schematics - ^ Curtis Electromusic Product Overview
- ^
*What chip do I have in my synth?*at www.synthtech.com - ^
*The Prophet from Silicon Valley: The Complete Story of Sequential Circuits*by David Abernethy, CreateSpace Independent Publishing Platform, 2015, ISBN 1512198323, pp. 128-129 - ^
^{a}^{b}Build a better music synthesiser by Thomas Henry, Tab Books Inc, 1987, ISBN 0830627553 - ^ Curtis Electromusic Customers and Instruments
- ^ Synthesizer Database by Moogulator
- ^ CEM chips in Doepfer Modules by Pierre Serné, 28 Feb. 2012
- ^ MIDIbox 3396
- ^ Digisound 80 Synthesizer Modules
- ^ Wikipedia:CEM and SSM chips in synthesizers

## Further reading

*Synthesiser IC's*by H. P. Baumann, Elektor 078, Oct 1981, pp. 10-18*Electronic Music Circuits*by Barry Klein, Howard Sams, 1982, ISBN 067221833X*101 analog IC designs*, Interdesign Incorporated, 1976*201 analog IC designs*, Interdesign Incorporated, 1980

## External links

- Curtis Electromusic - archived
- Alfa application specific ICs
- What a Difference a Chip Makes a quarter page advertisement in Contemporary Keyboard, February 1980
- Pictures of dead CEM chips at Stromeko Synth World
- A Monolithic Voltage-Controlled Amplifier Employing Log-Antilog Techniques, by Douglas R Curtis, JAES Volume 24 Issue 2 pp. 93-102, March 1976
- Synth's Inside Out
- About the CEM3340 - ICs for Electro-Music (Part 1) by Charles Blakey, Electronics & Music Maker, March 1981
- About the CEM3320, CEM3330 and CEM3310 - ICs for Electro-Music (Part 2) by Charles Blakey, Electronics & Music Maker, April 1981
- CEM (Curtis) Love Thread, Gearspace.com, Jul 2015

## YouTube

### Data sheets

CEM3310, CEM3310 long,CEM3312, CEM3320, CEM3320 long, CEM3328, CEM3330, CEM_3330-3335 long, CEM3340, CEM_3340-3345 long, CEM3350, CEM3360, CEM3365, CEM3371, CEM3372, CEM3374, CEM3378, CEM3381, CEM3389, CEM3391, CEM3394, CEM3396, CEM5508, CEM5530

Some are also freely available from Synfo.nl