Isn’tses - The Fort Processor
Instructions and construction details
The Fort Processor is a touch and light controlled synthesiser and audio effect circuit designed
by Isn’tses for Fort Process festival 2018. The event is held at Newhaven Fort on the Sussex coast,
and Isn’tses have based the design and artwork of the instrument on the layout of the site, with
inspiration from the surrounding landscape and ocean.
The circuit consists of:
• A section which distorts and octave-divides incoming audio (eg from a radio, walkman, mp3,
synth etc)
• Squarewave oscillators controlled by touching the metallic drawings across the centre of the
circuitboard with fingers, and also by a light sensor (best played using flashing/colour-changing
lights or moving shadows)
• A chopper/ring-modulator which rhythmically slices between the distorted input signal and the
oscillators,
• A ‘Twin-T’ section; a classic kick drum circuit mutated into a mysterious bass oscillator/drum/
drone/filter which is influenced by the audio input.
If no audio input is connected, the circuit instead uses feedback and acts as a self-contained synth.
The Fort Processor is, like Fort Process itself, a space for experimentation and exploration. Certain
parts of the circuit can be altered by the builder. If you wish to heavily modify/circuitbend it we
recommend using sockets or pins in order to try out different connections or component values,
most notably across the two rows of holes which mix the different octaves from the 4040 chip. We
would love to hear about any modifications or discoveries you make.
Please note that the audio jacks are wired in a slightly unorthodox manner which means that you
must use a stereo cable, or a stereo to dual-mono one. A 3.5mm mono jack (ie eurorack patch cable)
will not work in either the input or the output of the Fort Processor.
When building the circuit please pay special attention to the notes on the bill of materials and the
diagram below. The circuit has evolved so some components are different to those marked on the
PCB, and there are some crucial connections which must be made using small wire jumpers - the
cut-off legs of soldered resistors work well for these.
We recommend sticking small rubber feet on the underside of the board, or mounting it in on
a base or in a box with bolts thru the provided holes, or placing it on a soft and non-conductive
surface when you play.
Please contact us if you have any questions or need any advice about building the circuit.
More info and background on the project can be found at http://isntses.co.uk/blog
