Liches Brew (Pd patch for Befaco/Rebel Tech Lich)

[Liches Brew]

A malformed complex noise source and CV generator.

Liches Brew is a noise and CV generator with a bent towards classic sci-fi sound effects. Radio signals, computer brains, howling wind, avalanches, etc. Four varieties of audible noise and chaotic signals are available, as well as stepped and smooth random CV outputs and a clock.

I made this as a way to consolidate some of my favorite noise patches into a single device with simple, but flexible controls, and as a way to learn Pure Data which I hated at first but now am in love :anatomical_heart:

I plan to update this in a few ways, but it’s a lot of fun to play with already so I went ahead and posted it. I’ll need to figure some more stuff out before I can get it working entirely as I want, but the main changes will be getting a smoother spread of clock frequencies for the stepped and smooth CV output section and adding an external clock input for that section.


Pure Data or a device that can run Pure Data patches. Befaco/Rebel Lich or OWL.



Liches Brew is based on a pair of oscillators being modulated by malformed sample and hold circuits. I’m not sure exactly what is wrong with the S&H circuits, but I liked the way these sounded better than when they functioned properly so I kept them. It sounds more like track and hold to me, but I haven’t confirmed if that’s actually what they’re doing.

Additionally, Oscillator 1 applies a fixed amount of frequency modulation to Oscillator 2. All sounds and signals available at the outputs are derived from this core.


Knob A controls the master sample rate of the system. This control is asymmetrical, with one of the halves operating at a fraction of the other’s sample rate. At high sample rates, a wide variety of multicolored noise and tones can be produced. At lower sample rates, pseudo-random sequences, radio signal sounds, and chirpy server noises will emerge.

Knob B controls the spread between each side’s oscillator. At its fully CCW position, oscillator 1 will be at its highest frequency while oscillator 2 will be at its lowest. As the knob is moved clockwise, the oscillators move in opposite directions, passing each other in the middle. At its fully CW position, oscillator 1 will be at its lowest frequency, and 2 at its highest.

Knobs C and D control the amount of modulation affecting oscillators 1 and 2 respectively.

Button 1 switches between modes at the Left Output. Both buttons and Gate inputs act like trigger inputs rather than gates.

Button 2 switches between modes at the Right Output.

Left Output passes two versions of the final, wide-spectrum signal. The first is a ring modulated result of the two halves, and the second is their sum with a subtle low pass filter applied.

Right Output passes more intermittent, low frequency signals derived from the sum output. The first is bandpass filtered at 1200 Hz and can range from vinyl-like crackle, to geiger counter clicks, to tonal bursts of sound. The second is lowpass filtered at 100 Hz, and can sound like thunder or or the rumble of an avalanche. This output is especially useful as a modulation source.

CV Out 1 passes a unipolar stepped random signal derived from the first half of the noise circuit. The clock rate of this is influenced by the master sample rate, but is not proportional to the main sample and hold circuits. The clock rate ranges in time from around 200 milliseconds to 2 seconds.

CV Out 2 passes a unipolar smooth random signal derived from the second half of the noise circuit, and shares a clock with the stepped random generator. The slew rate is proportional to the clock rate, so this signal should wander continuously, rarely hanging at any voltage.

Gate Output passes the clock that controls the smooth and stepped random output signals.

The Left Input will offset oscillator 1’s sample rate.

The Right Input will offset oscillator 1’s frequency.


v1.0.0 - [Rebel Tech Patch Library]
The Pure Data file is available on its own if you click on the Source tab.


Thanks for sharing your patch. Really rich noise source! :smiling_imp: Had fun with this today running on Lich with support from Zlob triple cap chaos and Skorn da Bask.

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