There are lots of excellent sounding filters available in modular land.  I have a pretty good collection, myself.  Well, today I tried doing a comparison of four different 4-pole (24 db/octave) low pass filters.  It’s not easy to keep all things equal, but I tried, as follows.

• The audio input to all four filters is a sawtooth wave from a MOTM-300 VCO.  It’s being stepped in a repeating pattern.
• The inputs are all somewhat attenuated to avoid over-driving effects.
• The 1V/octave CV input of all four filters is a single MOTM-800 envelope generator.
• The initial cutoff frequencies of the filters are as close as I could get them by making them resonate and matching their pitches.
• The resonance (Q) is set all the way down, since I don’t have a good way to set them all to an equivalent resonance.
• I made an attempt to keep the signal levels even.
• The recording is mono.

And the four filters are:

• Synthesis Technology MOTM-490 VCF
• Oakley Filter Core Super Ladder VCF (Transistor version)
• Mattson Mini Modular VCF
• Mankato VCF

I’m not saying in what order these filters appear in this recording.  It is not the above.  You’ll have to guess.  I’m making a post on Muff’s where anyone interested can comment.  (You can comment here, too, but I’d rather have the discussion on Muff’s.)

What strikes me is that all four sound remarkably alike!  You can hear subtle differences.  This is NOT meant to be a shoot out of which is “best”.  Truth is that these filters are quite different in overall features, one from the other.  They are not mutual replacements.  But they all have a 24 db/octave low pass output.  Here it is: