Doug Curtis

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Doug Curtis (March 8, 1951 – January 10, 2007) was the founder of Curtis Electromusic Specialties and OnChip Systems. Curtis was the designer of many original analogue ICs, which have been used in a number electronic music instruments. He was described in Keyboard magazine as "one of the most important and least known synthesizer pioneers of the 20th century".[1]

In high school with an interest in sound and music electronics, he designed and built a synthesizer. He majored from Northwestern University, with radio-TV-film. While here he perfected several more synthesizers. Upon graduation, he qualified for a post as junior engineer by showing circuit boards of his designs. He entered a competition to design a semi-custom chip and as a result was offered a job at Interdesign, where he worked for four years.[2]

He founded Curtis Electromusic Specialties, which produced the integrated circuits that were used in a variety of analog synthesizers for decades. There are several patents in his name. In 2006 he was inducted into the San Jose Rocks Hall of Fame for technical contributions to music. In 1988[3] with the advent of digital technology, Doug formed the company OnChip Systems.[2]

Instruments with CEM ICs are said to have that Curtis sound, described as "fantastically saturated, brash and powerful".[4]

In 2016, it was announced that the CEM3340 VCO would be remanufactured by On Chip using the original design with a revision to the VCC specification.

Curtis Chips in Post-Modern Synth Arena[edit]

The CEM3340 IC is seeing somewhat of a renaissance due to its reissue by a few semiconductor companies (ref to go here). Notably, one such company appears to have garnered the blessing of Mary Curtis (Doug's widow) herself, touted in these words appearing on a graphic on their sourcing page:[5]

"A message from Mary Curtis":

Many of you who are active on synth forums have recently contacted us regarding another company's claim of producing VCO chips that are the equivalent to the CEM3340 that was used in many legendary synthesizers.

To avoid any confusion, please know that there is only one manufacturer of the authentic CEM3340 designed by my late husband, Doug Curtis. Any claims, use of this product designation, and use of the name Curtis Electromusic by other companies are made without permission from OnChip Systems (our current company name) or the Curtis Family.

As much as Doug would be humbled and so very happy about the legacy his products enjoy, we can assure you that as a person of the highest integrity he would be deeply saddened by the attempt of others to trade on his name and to make unsubstantiated claims of equivalency to his original inventions.

In his loving memory and gratitude for the community of musicians and synthesizer enthusiasts, Doug's family is committed to making his authentic designs available as demand presents itself. Thank you for your continued support of Doug's analog synthesizer legacy.

- Mary Curtis and our daughters, Ashley and Julia

The Thonk website link also provides some graphics of the original datasheets for the chip.

(Post)-Modern Designs Using The Curtis Chip[edit]

For detailed information and circuit variation discussion, please see the excellent article published at The Electric Druid CEM3340 VCO Designs[6]

Company Model Circa Promo Blurb
Malekko Manther 2018 The heart of this beast is a coveted CEM 3340 based VCO IC chip. The analog filter is based on an ssm2044 chip.
Behringer Neutron 2018 The pure analog signal path of the Neutron is based on the v3340, a smt clone of the CEM3340 VCO chip, with variable oscillator and LFO shapes which can be blended or switched for unique sound creation.
Roland MKS-80 Revision 4 1984 CEM3340 VCO circuit saw release as a part of several implementations, including the classic Jupiter 6.
Roland SH-101 1980's The Roland SH-101 used a single CEM3340 paired with sub oscillator, fed into classic Roland ota filter based of IR3109.
Oberheim OB-Xa 1981 The OB-Xa is a legendary polyphonic synth design. its brash sound is found on many seminal albums from the 1980s. it features both 2-pole and 4-pole filters.
Sequential Prophet 5 Rev.3 1980's The Prophet-5 is a legendary and classic synth design, touted as one of the 14 most important synths in electronic music history. it sported 5-voice polyphony and a polymod section, which allowed using its oscillators as modulation sources.
Sequential Prophet T8 1980's The Prophet-T8 is a legendary and classic synth design "a monstrous 8 voice polysynth",[7] most known for its weighted keybed, and for adding velocity and polyphonic aftertouch as modulation sources.

See also[edit]


  1. ^ Ryle, Marcus (April 2007). "Keyboard". Archived from the original on 7 November 2007.
  2. ^ a b Doug Curtis at
  3. ^ "San Jose Rocks". Archived from the original on 2017-09-12. Retrieved 2012-11-18.
  4. ^ Description at Sequential Circuits Prophet-600 sounds
  5. ^ Curtis CEM3340 IC – Reissued VCO Chip
  6. ^ The Electric Druid CEM3340 VCO Designs
  7. ^ Sequential Circuits Prophet T8

External links[edit]