Wall of Ice

What this section does

Everything the pedal does starts here. The input stage receives whatever you plug in — guitar, bass, synthesizer, a vocal through a preamp — protects it, and hands it to the rest of the circuit at the right level. Right behind it sits a steep, adjustable high-pass filter that decides how much low end reaches the distortion stages.

Placed before distortion, the high-pass filter changes the spectrum feeding the clippers. Placed afterward, a high-pass would reduce the low end of the already distorted result. Wall of Ice provides the first kind of control, with a smooth transition around its selected corner.

Low-frequency reach and its limits

Malice is intended for guitar, bass and synthesizer sources. Its drive keeps a broad bass response, while Wall of Ice gives the player a deliberate low-frequency cut before clipping. This describes the design intent, rather than flat response through every mode of the pedal.

• The production brief reports every inter-stage coupling corner below 2 Hz and low-frequency response flat to ±0.1 dB from 20 Hz upward with filters open. Wall of Ice is deliberate filtering; CRz has its own low cut near 100 Hz. These are separate from coupling losses.

• The input stage adds +6 dB before the later processing stages. This gain distribution is a design choice; it does not establish the assembled pedal’s input-referred or output-noise performance.

• Clockwise means more. Every knob on the pedal adds as it turns clockwise. On this section, clockwise admits more low end.

The input stage

The JFET input stage is intended to limit loading on passive pickups. The available Butter Panel.net export (1 October 2026) shows two 4.7 MΩ shunt resistors, one on each side of the input coupling network. Where the coupling capacitor passes the signal, their combined resistive loading is approximately 2.35 MΩ, before accounting for the 100 pF RF shunt, source impedance and other frequency-dependent effects. This is a circuit estimate, not a measured input-impedance sweep.

• Two 4.7 MΩ resistors do not make the complete input 4.7 MΩ across the audio band. Pickup inductance, cable capacitance and the RF shunt influence the loading and resonance; a higher resistance is a voicing choice rather than a universal improvement.

• The export includes a 100 pF RF shunt behind a series resistor and a 22 nF input coupling capacitor. The coupling capacitor provides DC isolation; the bias resistor behind it still contributes to the AC input load.

• A JFET-input amplifier is used at the first stage, where its noise contribution will be amplified by later stages. The device noise figure is not a measured whole-pedal noise specification.

• +6 dB of clean gain applied here, at the quietest point in the chain, so the signal arrives at the drive stages well above their noise floor.

• Protection diodes that never conduct in normal use but catch static discharge and cable-plugging spikes before they reach the amplifier.

• The coupling capacitor and its 4.7 MΩ bias resistor set a corner at 1.5 Hz — the lowest note on a five-string bass is 31 Hz, and the input does not know it is there.

This is the most sensitive node in the pedal and it is treated that way on the board: the input network sits within a few millimetres of the amplifier pin, on a single layer, with nothing routed near it. The protection diodes guard the hardware against static and cable-plugging spikes; they do not make the input a line-level input. The amplifier handles roughly ±6 V cleanly, which covers instrument level, line level, keyboards and most synthesizers with margin. Only the hottest sources — modular synthesizers running at ±10 V, for instance — exceed it; the input will not be damaged, but the first amplifier will distort, and a small external attenuation is the fix.

The high-pass filter

The filter is a fourth-order Butterworth high-pass model: no passband ripple and an ultimate slope of 24 dB/octave below the corner. The response falls smoothly through the corner; frequencies just above it are still affected. At one octave below the corner, ideal attenuation is about 24 dB, rather than silence.

The corner frequency sweeps from roughly 12 Hz fully clockwise to 490 Hz fully counter-clockwise. Clockwise admits more low end. The filter remains in the signal path at its broadest setting, so its own response and other coupling stages still contribute to low-frequency attenuation.

Because the filter is placed ahead of the notch and the drive stages, its setting changes how those stages behave, not just what you hear at the output. Two practical consequences:

• Low-end cleanup before distortion tightens the drive and reduces intermodulation — the low notes stop smearing the high ones.

• The notch filter that follows becomes more precise once the low end is controlled; the two are meant to be used together.

Specifications

Serviceability

The board receives ±15 V through local filtering and isolation resistors. These help limit supply coupling between boards. The input and power board include protection components, but fault damage and the required repair must be checked rather than assumed.

Notes

The +6 dB of preamp gain is intentional and is accounted for in the rest of the pedal’s gain structure; bypass and engaged levels are matched at the output stage. Suggested settings and the knob’s interaction with the notch and drive stages are covered in the user’s guide.

This pedal was built to be tried on things pedals are not usually tried on. Bass, synthesizers, drum machines, vocals, a whole mix — the input and the filter will treat them all the same, and the results are often the interesting part. If you find something that works, or something that doesn’t, tell us. The design will keep improving, and that feedback is how.