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The HM2040 is an equivalent of the now obsolete SSM2040 voltage controlled filter IC.  The HM2040 voltage controlled filter module can be used for all circuit configurations originally designed to use the SSM2040 integrated circuit.  The module is housed in a rigid potted enclosure with 0.1" pitch legs spaced 0.7" apart.  Shortened pin identifies pin 1.

  • +/-12V* or +/-15V Supplies
  • 4 filter sections in one package
  • Very low noise
  • Low distortion
  • Low control feed through
  • 10,000 : 1 Sweep range
  • Works with any circuit utilizing the (obsolete) SSM2040 IC.

Low offset and good stability is achieved by using closely matched transistors throughout the design.  Differential stages are implemented with monolithic (same die) transistors.  These matched pairs are then encapsulated in a thermally conductive potting compound assuring that all transistors remain at the same temperature.  The thermal mass of the potting reduces the effect of self heating and short term temperature fluctuations in addition to providing good mechanical resilience.

A number of example circuits is given on the HM2040 datasheet.  An additional example circuit is given for a 2-pole state variable filter design with voltage controlled resonance.

Prices, stock level and ordering information can be found in the Shop.  A more in depth look at the filter can be found in the SSMT patent.

Demo & Testimonials

This demo was created by Matt J and demonstrates the SSM2040 configured as a 4-pole low pass filter

Galactic Horizon

"This was great fun to build! This demo shows The HMVCO1c with a little PWM fed in to the HM2040. Envelope on filer CV 1 is from the Frequency central System X Env. A tempo synced LFO from Silent way is fed in to CV 2."

“I have used them before in my Model 2040 it sounded exactly 100% like the SSM2040 as i made the pcb so you can swap between a HM2040 and SSM2040.
I am huge fan of this filter design  For me it’s the best filter ever, and yours are the only on the planet that sounds 100% spot on.”

*Datasheet specifications based on +/-15V supplies.
George Hearn,
19 Jul 2009, 11:50
George Hearn,
1 Oct 2009, 04:55
George Hearn,
13 Jul 2009, 03:29
George Hearn,
11 May 2010, 01:47