Multimode Ladder Filter

Multimode Transistor Ladder Filter with Red Mode feedback distortion

The updated "skiff friendly" design of the MML Filter now features bipolar "attenu-verters" for the CV controls as well as an all new RED MODE!

This new mode activates a feedback distortion circuit capable of actually changing the pitch of the notes coming in to the filter in a musical way that adds instant variety to acid basslines, creates weird and strange alterations to drones or adds some nice overdriven distortion to whatever goes into it!

The Multi-Mode Ladder (MML) Filter is based on the classic transistor ladder low pass filter by Dr. Robert A. Moog. This filter updates the classic 4-pole ladder design to provide Band Pass and High Pass filter responses as well as the traditional Low Pass filter. There are 2 bipolar controls with attenu-verters for the cut-off frequency plus a CV input for the resonance.

The core of the circuit features a fully discrete transistor design with an op-amp buffered output, this allows soft saturation of the input signal to get the classic overdriven tones of the ladder filter. A bass compensation circuit has been included to retain the bass response in Low Pass mode when the resonance is increased. The bass compensation also helps to improve the response of the High Pass filter.

The RED MODE is activated/de-activated by holding the MODE BUTTON for 0.3s. In this mode the filter cut-off, input volume and resonance all interact and the effect is to produce alterations to the incoming frequencies. The pitches of the audio coming into the filter also affect the alterations as well selecting between Low Pass, Band Pass and High Pass filter modes whilst in red mode.

Features:
· LOW PASS, BAND PASS AND HIGH PASS MODES.
· RED MODE FEEDBACK DISTORTION.
· CV CONTROLLED RESONANCE.
· ADDED LOW FREQUENCY COMPENSATION.
· SOFT SATURATION OF INPUT.
· 2 X BIPOLAR ATTENUVERTER CV INPUTS.

https://www.dannysound.com/modules/mml-filter