Isn'tses FORT PROCESSOR - a psychogeographic noise synth + effect circuit

This is something we’ve been working on for a while and was first released for Fort Process festival 2018 so it’s about time I properly posted about it here! :oops: Really proud of how it turned out, we are now on a 2nd revision of the PCB and have a complete kit for sale via Thonk :slight_smile:


The Fort Processor is an experimental noise synthesiser and audio effect circuit designed by UK harsh fun noise duo ISN’TSES (Tim Drage & Lisa McKendrick) for Fort Process sound art festival 2018. This event takes place in the tunnels and bunkers of Newhaven Fort on the Sussex coast, and the electronics and artwork of the synth are based on the layout of the site, with inspiration from the surrounding landscape and ocean.

Demo video:

The synth is controlled by light, touch pads, 3 knobs, and a trimmer. Audio is created and manipulated by four sections which have been combined using a circuit-bent approach:

  1. The audio input, (3.5mm) used to connect devices such as a radio, walkman, phone, tablet, mp3, instrument etc. This signal is distorted using high gain then run through a frequency divider to add two noisy sub-octaves. When no input jack is connected, the circuit feeds back and self-oscillates.

  2. Squarewave oscillators pitch-controlled by a Light Dependent Resistor located at the top right of the PCB. This LDR can be played by moving lights near it or by blocking the light. The resulting sound can be further modulated by the touch pads which are the metallic drawings across the middle of the circuit board. Touch two or more of these at once to alter the sound. This can be understood as a live circuit-bending effect.

  3. A variable-speed chopper, controlled by the 2nd knob. This rapidly slices between the distorted input/feedback signal and the light-controlled squarewaves. Turning the knob changes the speed, creating various ring-modulation, tremolo and cut-up effects.

  4. A bass oscillator/filter/beat/drone generator, mutated from the classic ‘Twin-T’ analog kick drum circuit. This is triggered and influenced by the audio input and is controlled by the 1st and 3rd knob in conjunction with the trimmer pot. Knob 1 controls the decay envelope; turned anticlockwise this produces more percussive sounds, while turning it clockwise makes bass drones. When turned fully-clockwise it gets quiet to allow the other noises to cut through. The 3rd knob and the trimmer pot interact with each other to control the pitch of this section. The trimmer can be gently turned with a small screwdriver and can be viewed as a tuner to achieve either a resonant drum-like sound, or a more continuous bass tone. The trimmer should be tweaked before playing according to each users personal preferences. Expect random and unpredictable results from this section according to how the rest of the sections are influencing it.

The Fort Processor is powered from a 9v DC, centre-negative power supply, ie a BOSS-style guitar pedal PSU. Other polarities or voltages will almost certainly damage/destroy the circuit, requiring at least the ICs to be replaced, so be careful! It is possible to wire up a 9v battery too, contact us for info on this.

The fort processor is available as a full DIY kit, as a bare PCB which you can build using your own components or display as an art object, and occasionally as a complete built synth. There are 2 versions, the original green one (more open to experimentation but a bit harder to build) and a new black one. Details and build info/BOMs -

Green or black bare PCBs can be got from us directly, ordering info here:

Kit version from Thonk:

We will also consider possible trades of a PCB for other interesting diy synth/eurorack/noise stuff, let me know any offers.

There’s more info about the process of designing this circuit:

Let me know any questions :slight_smile: Audio demos etc soon

(hope it’s cool to link to the order pages? if not let me know and i will edit)


In case anyone is interested we are doing a workshop at Thonk on the 23rd, come along and build a Fort Processor if you are in the area, or please spread the word to anyone you know who might be:

Unboxing video of the original PCB from one of the first people to buy one :slight_smile:


LONDON Fort Processor workshop. 1st June, at IKLECTIC, Old Paradise Yard, 20 Carlisle Ln London SE1 7LG - right near Waterloo station. The workshop runs from 11am for about 3 hours, and is suitable for complete beginners to soldering as well as more experienced synth builders/circuitbenders.

Event page:
Tickets £65 from (same price as buying the kit on it’s own plus you get our help to build it!)

and read more about the Fort Processor here -

also, here’s part 2 of the afformentioned build video

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Promo video for the workshop:

All tools and materials will be provided but if you feel like bringing your own and/or any bits for modifications then feel free, and/or bring something to play thru the circuit (eg walkman, radio, other small synths). There will be a short jam afterward where everyone can try out their Fort Processor :slight_smile: