Mad Science Lab

SSM 2040 Voltage Controlled Filter Chip History

SSM 2040 VCF



The SSM 2040 filter chip was designed by Dave Rossum of Emu. Emu produced this SSM evaluation board with all SSM chips needed to create an analog synth.

After experimenting with the board on the left, I decided to build a 2040 filter for my personal use.



This is my first prototype of the SSM 2040 used as a Low Pass filter.

The SSM chip is on the left in the middle. On the right is a bread boarded version of a single low frequency oscillator. (LFO)

I wanted to compare the filters made by Curtis and SSM side by side so I built this unit and hooked it up to various synths and drum machines.

curtis filter on the left

SSM board by emu on right

mounted in a case so it could be portable



rev 1.0

1st run of production boards SSM VCF boards

Several changes made to improve performance

This is my personal stereo unit so I can easily compare changes to the boards. Here the 2 boards have different type of capacitors, big ones on the left , small ones on the right. I now use high quality caps different from both of these early boards.



Early SSM chips built by certain factories had very poor rate of actually working. This and the factories lack of ability to improve defects caused Sequential to switch to curtis chips in later versions of Prophet 5's. Also Sequential did not have to pay royalties to Emu, since Emu had a hand in the design of these chips, once the Prophet 5 had all Curtis chips.

The chips I am using are from one of the Last Revision Production Runs in 1988 at Japanese Foundries. These are far superior quality than the early 80s run in South Asia. (word of mouth, hard to verify) The main thing is they sound great, and they can be overdriven to create interesting sounds. Sequential Circuits Prophet-5 R1 and R2 use this SSM 2040 filter. NOT Rev 3 prophets, which use Curtis chips.







SSM 2040 Manual page

More info: Serial # 2003-03 Inside the monster


Back to Main SSM 2040 VCF page


Sequential Circuits Synthesizers Page

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