VCO, Comparator and Sample & Hold Combo


Tromsø is a combination of 3 basic utility modules: VCO, Comparator, and Sample & Hold. Internal normalization 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 old-school 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.

Tromsø is inspired by the first analog downsampler and bit distortion of its kind, Distortotron

The VCO of Tromsø module can track one volt per octave when the Attenuator on the FM input is fully open, making it possible to have the downsampling effect track with the pitch of a played note.

All three utility modules of Tromsø can also be used completely independently because the normalization disappears once you plug a connector into the inputs.


  • 5HP
  • triangle core VCO
  • exponential FM input with Attenuator Knob
  • tracks volt per octave over about 5 octaves when the attenuator is fully open
  • switch to change the range of the VCO – high= 15Hz-45kHz, low=50s – 50Hz
  • VCO output is normalized 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 a gate input, input, and output
  • switch to select mode: Sample & Hold (samples at the rising gate and then holds) or Track & Hold (at high gate tracks, at low gate holds)
  • front panel from aluminium or oak wood with custom knobs
  • handmade locally by Bastl Instruments in Brno, Czech Republic

Technical details

  • 5HP width
  • PTC fuse and diode protected 10pin power connector
  • 45mm deep
  • current consumption: +12V: <35mA, -12V: <35 mA
  • pdf user manual download

DIY kit

You can build your own Tromsø with our DIY kit. Go through the complete assembly guide below and make sure that you understand all the steps.