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The SSM2040 IC is a 4-pole filter from Solid State Micro Technology for Music (SSM). Regarded as one of the best sounding filters, because of the way resonance and small amounts of soft distortion when overdriven, can add harmonics to the original signal.[1]


Designed by Dave Rossum of E-mu Systems and used in the first 2 versions of the Sequential Circuits Prophet 5. Early SSM chips were often defective, and having to pay royalties led Sequential to switch to Curtis ICs in later versions of the Prophet 5.[2][3]

Circuit building block

The device's cutoff frequency can be exponentially voltage controlled over a 10,000 to 1 range. It is an extremely flexible circuit building block which can be used in virtually any active filter design including low-pass, high-pass, band-pass and notch. Roll-off characteristics can be selected to be Butterworth, Chebyshev, Cauer, Bessel or any other filter type.[4]

Clones and schematics

In chronological order:

Synthesizers etc. using the SSM2040 or clone

See also


  1. ^ The SSM2040 Integrated Circuit, by James Gideon, 2006
  2. ^ SSM2040 Voltage Controlled Filter Chip History, Mad Science Lab 2008
  3. ^ SSM2040 VCF with LFO, Mad Science Lab 2008
  4. ^ SSM2044 data sheet
  5. ^ News and Notes, January 1983, Digisound Ltd.

Further reading

  • SSM2044 data sheet
  • Build a better music synthesiser by Thomas Henry, Tab Books Inc, 1987, ISBN 0-830-62755-3, Chapter 6: A four-pole lowpass VCF – SSM2040
  • Electronic Music Circuits by Barry Klein, Howard Sams, 1982, ISBN 0-672-21833-X, pages 125-126, 135-137, 141
  • Two ICs For Electronic Music – SSM2020 And SSM2040 by Dave Rossum, Electronotes 78, Volume 9, 1977, p. 15
  • Reader's Circuits – VCF With SSM2040 by Rich Ryan, Electronotes 84, Volume 9, 1977, p. 17
  • A Fourth Order State-Variable Filter by Bob Chidlaw, Electronotes 99, Volume 11, 1979, p. 3
  • Musical Applications of Microprocessors by Hal Chamberlin, Hayden, 1985 ISBN 0-8104-5768-7, pages 218-220, 599, 603
  • The Smooth Phaser by Thomas Henry, Electronic Musician, June 1988, pp. 78, 80-83.

External links