Shruthi-1 4-pole Mission Filter Board - One Board to Rule Them All

via Mutable Instruments

"One board to rule them all… This filter board is probably the most advanced 4-pole core for the Shruthi-system! It uses the same “Pole-mixing” technique introduced in the Oberheim Xpander to provide a cornucopia of filter responses. It also provides 4 different settings controlling the “flavour” of the resonance, clean and liquid, MS-20 style, wobbly/chaotic, and a combination of the MS20 and wobbly modes.

The filter core is based on a SSM2164, for a very low-distortion and pure sound. A LM13700 is used as a global VCA and for resonance control, with loudness compensation.
Using this filter board

Please make sure that both the analog (CV1 to +5V) and digital (RX to +5V) ports of the filter and control boards are connected.

Beware! Only the Shruthi-1 firmware v0.96 (or above) generates the digital signals required to control the mode selection and routing matrix. In addition, it is not possible to use simultaneously the 4-Pole Mission filter board and the Programmer since they will be both accessing at the same time the digital extension port. To activate the 4-Pole Mission filter board, select 4pm in the system settings page. If you don’t do so, it is likely that it will emit glitchy filtered sounds everytime you navigate through the pages.

When pressing the S2 switch (Filter page) a second time, a new page is displayed allowing you to configure the filter routing.

Cut res mod fla
100 33 lp4 liq

The parameters are the following:
cut (cutoff): Cutoff frequency, conveniently repeated on this page.
res (resonance): Resonance level, conveniently repeated on this page.
mod (mode): Filter mode. See below.
fla (flavour): Resonance flavour. See below.

The following 15 filter modes are available:
lp4: 4-pole low-pass.
lp3: 3-pole low-pass.
lp2: 2-pole low-pass.
lp1: 1-pole low-pass.
hp1: 1-pole high-pass.
hp2: 2-pole high-pass.
hp3: 3-pole high-pass.
bp2: 2-pole band-pass.
bp4: 4-pole band-pass.
notch: notch filter.
phaser: phaser.
h2lp: 2-pole high-pass and 1-pole low-pass (band-passlike).
h3lp: 3-pole high-pass and 1-pole low-pass (band-passlike).
n+lp: notch and 1-pole low-pass.
p+lp: allpass and 1-pole low-pass.

The 4 resonance flavours are:
liquid: standard, close to the CEM or Roland designs (no loudness drop).
ms: Korg-35 style soft limiting is introduced in the signal chain.
wobbly: The 1-pole output is fed back to the filter cutoff frequency for a rubbery chaotic and modulated resonance.
whacky: A combination of the ms and wobbly modes."

Full details on Mutable Instruments here.

We now know what the recent SoundCloud demos were for.


previously posted