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 attenuverters 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.

In the red 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:

• Lowpass, Bandpass and Highpass Modes
• Red-Mode Feedback Distortion
• CV-Controlled Resonance
• Added Low Frequency Compensation
• Soft Saturation of Input
• 2x Bipolar Attenuverter CV-Inputs