Wednesday, August 27, 2008

The Mankato filter

Here's a filter design that's been around for a while now, and originally designed by Thomas Henry.
I thought I would get some more info about it, as it was being used in the previous post on the Klee Sequencer.
The Mankato Filter is a four-pole lowpass filter with positive and negative outputs at every pole, giving you slopes of 6 dB/oct, 12 dB/oct, 18 dB/oct, and 24 dB/oct simultaneously. the negative slope outputs allow you to use the Mankato as a quadrature sine oscillator with 8 available phases. the Mankato will self-resonate from subaudio to superaudio, and responds to one volt per octave through its unattenuated control inputs. the signal inputs are DC coupled, which allows you to use the Mankato as a voltage-controlled slew limiter. The picture shows the Mankato filter as produced and sold by STG Soundlabs, in the MOTM format, albeit cosmetically closer to the Moogs and Synth dot com modules.
Some sample links are below via Magic Smoke Electronics, who also produce a PCB , should you fancy building one yourselves from scratch :-)
Mankato Sequence 1
Mankato 6db
This second demo uses two Mankato's and here's how it was done:
"I fed an ARP Odyssey into Mankato 1; that's the low drone you hear at the very beginning. For CVs I had a standard LFO modulating Mankato 2 -- set to oscillate -- and the output of the prototype modulating Mankato 1. Various settings of the LFO, Mankato 2 (acting as a VC-LFO), and Mankato 1 (acting as a VCF) yielded all sorts of craziness. Very little tweaking was done on the Ody. I didn't really need to! ;-) There are a few spots where it sounds like there's a splatty "distortion" -- this is actually the VCLFO driving up into the audio range. Tip: Listen to it on a system with good bass response. The difference is pronounced. Crank that subwoofer and you'll get some serious rumbleys!"



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