Summary

Compact 6HP VCF for Eurorack Modular synthesizers

This is a state variable filter using the same core as our 2Q12 filter but substituting multiple unattenuated F and Q CV inputs with some on board attenutaors. Like the 2Q12, this filter has a nice fat sounding low pass output. The two pole filter has simultaneous -12dB per octave roll-off for high pass and low pass and a -12 db wide (-6dB either side) bandpass output. It has voltage control of cutoff frequency (F) and voltage control of resonance (Q). F and Q are adjustable with panel controls and from external sources using two F CV inputs and a Q CV input. One F CV and the Q CV have attenuators.

A demo of the 2Q12 which uses the same filter core

The videos, courtesy of Randy Piscione, supplement the main demo:

2 pole to 4 pole Comparison

The frequency response is exponential at 1Volt/Octave.

The design uses a positive feedback resonance circuit that maintains a high input signal level as resonance is increased. This enables low noise output regardless of the resonance. The input level control can be used to provide a smooth or clipped high pass output during resonance, further increasing the opportunities for sound experimentation.

IMPORTANT NOTE

This is a PCB and Panel set only. A set of 1 high quality PCB and 1 front panel ONLY are included. You will need to purchase your own components and build your own module. Comprehensive build instructions and BOMs are provided to help you source the components needed and we even provide links to shopping carts to simplify sourcing those components. Some product photos above show COMPLETED build.

Features

• Two pole 12dB filter
• Simultaneous high pass, low pass and band pass outputs
• Exponential 1V/octave response
• Voltage control of resonance
• Self-resonance adjustable
• Two frequency CV inputs FCV1 and FCV2. FCV1 also has an attenuator.
• One Q CV input with attenuator.
• Input level control
• 6HP Eurorack with our panel

Documentation

Comprehensive documentation, parts lists are provided in the documentation link for building, testing and calibrating the module.