Catalinbread Knight School Filter - DIY Kit

A "state-variable" low-pass: the secret weapon of tone shaping

Whether on a synth or a pedalboard, the low-pass filter is one of the most powerful tools to transform a raw sound into living material. The Knight School Filter follows this tradition with a simplified state-variable filter design: an architecture known for steeper slopes and a more spectacular sound than a simple passive "tone" filter. The result: you don't just darken the sound; you reshape the attack, dynamics, and sense of movement, as if you were "playing" the filter as much as your guitar.

Where many effects include subtle filtering, here the filter becomes the main effect. And that's precisely what makes it formidable in combination: placed after an overdrive, fuzz, or even modulation, it absorbs excess harmonics and brings you back to rounder, more "synth-like," sometimes downright organic timbres.

Who is this kit for and which styles does it excel in?

The Knight School Filter DIY Kit is aimed at guitarists (and bassists) who want to break away from the usual "drive + delay" setup and add a truly expressive control to their playing. If you enjoy tweaking your settings, stacking pedals, and discovering unexpected sonic territories, this is exactly the kind of effect that sparks riff and texture ideas.

Style-wise, it fits anywhere the sound needs to move and breathe: modern funk, psychedelic rock, stoner, noise, electro-rock, ambient, post-rock, and anything flirting with synth sounds. In the studio, it helps carve space in a mix, tame a fuzz that's too "chainsaw-like," or create cutoff sweeps in overdubs. Live, it's a performance tool: a quarter turn and you shift from a sharp drive to a thick, vocal lead.

Controls and operation: simple, yet (very) deep

The philosophy is clear: three controls, a wide range of action. The Filter knob sets the low-pass cutoff frequency: one end keeps the sound open (around 9 kHz), the other closes it down to about 280 Hz for a dark, round, almost "muffled" synth-style sweep. The Resonance (feedback) control feeds part of the output back into the input: the higher you go, the more the cutoff edge sings, with a formant impression and very musical "juiciness." Even at maximum, the filter does not self-oscillate, allowing you to push it far without losing control.

The Gain acts like a series potentiometer on the input, similar to your guitar's volume: useful for adjusting the level depending on the filter's place in your chain. At the start of a pedalboard, you can keep it high and manage volume with your guitar; in the middle of a pedal set (with more variable levels), it helps precisely dose what you "feed" the filter.

Finally, since this is a DIY kit, the experience goes beyond sound: the PCB is labeled for each component, and assembly familiarizes you with the basics of clean construction (orientation of polarized components, wiring potentiometers, integrating the footswitch and LED). A pedal that sounds great, but also a real hands-on pedal building lesson.

The sound

Expect an expressive and "aggressive" filter in the best sense: the cutoff is sharp, and the sense of control is immediate. At low resonance, the sound is smooth, almost "studio-like," ideal for rounding off distortion or taming harsh highs. Increasing resonance makes the filter more vocal: mids come forward, the sound takes on an almost synth dimension, with a harmonic peak that responds very well to your attack.

The real playground is placement: behind a fuzz, the filter swallows excess harmonics and brings out thick, moving textures, very much in a "Zappa-esque" style when you push gain and resonance. Behind a modulation, it can turn a chorus or phaser into darker, more cinematic pads. And if you like playing with your guitar volume, you'll appreciate how the filter follows level variations: it becomes an extension of your dynamics.

Technical specifications

Effects	Effects	Type	sector
Technology	Analog	Use	electric guitar
Format	Pedal	Color	Grey
EQ	Filter

Bypass	true bypass	Height	4.9 cm
Filter	cutoff frequency approximately 9 kHz to 280 Hz	Width	6 cm
Gain	series potentiometer on input (guitar volume type) to adjust level sent to the filter	Depth	11 cm
Resonance	feedback to enhance the "synth" character; does not cause oscillation even at max	Power supply	not included
Input	1 x 6.35mm Jack	Battery operation	no
Output	1 x 6.35mm Jack	Required power supply	9V DC, center negative