Fairfield Circuitry Long Life Filter

A state-variable filter with wide range and application. Versatile. Combining tilt and notch and boost equalization around a 2nd-order (-12dB/octave) state-variable core.

Very much a one-band parametric equalizer with gritty extras:

• Shelving filter, from low-pass to high-pass
• CV inputs for resonance (Q) and frequency (F)
• V/octave scaling synthesizer interface
• Fully variable Q goes well into tasty sweet self-oscillations
• Soft clip zener zesty mordant
• Expression pedal input controls center frequency

Uses

• Flexible tone stack allowing for careful tuning of desired response
• Stacking before/after other pedals for dramatic emphasis/deemphasis
• With an expression pedal for wah-type debaucherie
• Standalone channel strip EQ for outboard processing
• Integrated with a modular synthesizer mindset, can act as a VCF and a VCO
• With external CV control such as sequencers and keyboards

Long Life Controls

• FREQ: Corner frequency of filter. Summed with CV F input and expression input.
  Frequency range without external control 8HZ 6kHZ
• Q: Quality factor or resonance control. Before noon for softer equalization.
  Aggressive past noon.Self oscillates past 3 o’clock. Summed with CV Q input
• GAIN: Negative and positive gain of bandpass filter section allows for notch or
  boost of selected frequency (FREQ).
• TILT: Frequency response can be tilted around the center frequency. At one extreme,
  a low-pass response; at the other, high-pass. At noon, the response is flat.
  In between these points, various degrees of flat. In between these points,
  various degrees of shelving.
• VOL: Unity gain is around 2 o’clock for a flat frequency response.

CONNECTIONS

• IN: 1/4″ Instrument or line level input
• OUT: 1/4″ Output
• EXP: TRS expression pedal input or TS alternate CV input to control center
  frequency
• Q and F: 1/8″ control voltage (CV) inputs for Q and F with V/octave scaling on
  frequency.

Requires 9VDC center-negative tip supply that can deliver at least 150mA

Caution should be exercised when pushing high-Q settings. Strong oscillations will occur.

It is normal to get some hiss, even slight clicks, when the corner frequency is past 2 kHz

PRINCIPLE OF OPERATION

A state-variable filter with wide range and application. versatile. Combining
tilt and notch/boost equalization around a 2nd-order (-12dB/octave) state-
variable core.

It is very much a one-band parametric equalizer with gritty extras:

• Shelving filter, from low-pass to high-pass
• CV inputs for resonance (Q) and frequency (F)
• V/octave scaling synthesizer interface
• Fully variable Q goes well into tasty sweet self-oscillations
• Soft clip zener zesty mordant
• Expression pedal input controls center frequency