Low pass filter based around the Curtis CEM3328

The CEM3328 is a vintage 24dB/Oct Low Pass VCF IC.

The IC supports voltage control of resonance, and "Custom Tailoring of Volume vs Resonance", which allows the filters output level to stay more or less constant as the resonance is increased. Very handy!
Synths utilizing these super rad filters include:

Crumar Bit-01     
Ensoniq Mirage  
Oberheim Prommer

This is the third revision, changes with the second reversion are:

-The cutoff and res CV inputs have attenuverters instead of just regular attenuators, and the cutoff CV input is normalled to the CV bus on the power supply. If you have a keyboard spitting CV onto the bus (like me!), this gives you variable positive or negative keyboard tracking.
-V3 uses only 4-pin headers.
-V3 has a trim pot to boost the gain a bit on the output, and does not have a trim to dial in max resonance.


  • ? mA +12V
  • ? mA -12V
  • ? mA 5V
  • 37 mm deep
  • Ø 5.00 (1 Votes) Average Rating

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12 HP Filter
submitted Dec 5th 2013, 19:43 by plop | last Change Dec 5th 2013, 19:52 by plop

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