Tromsø is a combination of 3 basic utility modules: VCO, Comparator and Sample & Hold. Internal normalisation allows you to instantly use it as voltage controllable analog downsampler (or sample rate reducer if you like). The sample rate is set by VCO Rate and a sort of “dry/wet” mix effect which is achieved by adjusting the Threshold when in the Track & Hold mode.
This architecture was inspired by a machine called Distortotron made in 1994 – arguably the first analog downsampler and bit distortion of its kind. That machine came from a collaboration between Norwegian musician Mental Overdrive based in Tromsø and the inventor group Psybe (Svein Berge and Henrik Sundt). It was created from a need to bring back oldschool sampler aliasing and lo-fi effects and heavily influenced the sound of the album ‘Plugged’ which is the landmark of the so called Tromsø sound.
The VCO of Tromsø module can track one volt per octave when the Attenuator on the FM input is fully open which makes it possible to have the downsampling effect track with the pitch of a played note.
All 3 utility modules of Tromsø can also be used completely independently because the normalisation disappears once you plug a connector into the inputs.
- triangle core VCO
- exponential FM input with Attenuator Knob
- tracks volt per octave over about 5 octaves when attenuator is fully open
- switch to change range of the VCO – high= 15Hz-45kHz, low=50s – 50Hz
- VCO output is normalised to Comparator Input thus Comparator Output creates pulse waveform for the VCO (Threshold = PWM)
- comparator has Threshold Knob, CV Input for Threshold, Input and Output with indication LED
- S&H section has gate input, input and output
- switch to select mode: Sample & Hold (samples at rising gate and then holds) or Track & Hold (at high gate tracks, at low gate holds)
Build Document – Assembly Guide