FS01 Fill-In / Quad Switcher

Fill-In / Quad Switcher with dividers and bar counter TR 808 style


This module was designed to enable TR808 style drum machine pattern fills to be performed with 2 or more analogue sequencers. One sequencer is the main pattern sequence, whilst the other becomes the fill-in, being switched in every 2, 4, 8, or 16 bars. This removes the repetitiveness associated with all analogue sequencers.


The FS01 has 2 sections, a switcher and a unique kind of clock divider:

FS01 has 4 independent switchers on 2 channels (X & Y). There are 2 control inputs, X & Y, which have control over the 2 channels X & Y. Each switcher has 2 inputs (A & B) and 1 output to switch CV, Gate or even audio signals. The switchers can be used in reverse, giving 1 input being routed to one of two outputs (A/B).

The FS01 has a special kind of clock divider. The Bar/Step 1 clock input counts bars. Take step 1 out from any one of the sequencers and connect this to the Bar1 input. If your sequencer does not have a Step 1 trigger output, maybe one can be fitted (we can do this for the TH48). If not, just use the main clock signal, and divide it down by how many steps long the sequence is. With the Bar1 input to the FS01 connected correctly, it will count bars and every 2, 4, 8 or 16 bars a +5V gate is generated at the appropriate socket for the duration of the fill-in bar. These can be patched into the control inputs (or to another module). All fill-in control outputs are active and can all be used at the same time if desired.

In Short

  • 2 CV (or Gate) outputs can be switched into 1 CV input, e.g. 2 sequencers outputs into 1 synth input.

  • 1 CV output can be switched to 2 CV inputs, e.g. 1 sequencer alternately controlling 2 synth's.

  • 2 audio sources can alternately be switched into one audio input (on a synth, effect or mixer channel).


1 audio source can alternately be switched into 2 audio inputs (on a synth, effect or mixer channel).

Other Uses

Use fill-in control outputs to trigger sounds, e.g. take fill step 16 out to trigger a cymbal type sound every 16 bars.

Gating audio on/off. Patch in one audio signal into A, nothing into B. Switch the audio in and out in time with the music for interesting gating effects.

New Waveforms
By feeding two different VCO waveforms into A & B inputs, then switching between them at high frequencies, interesting new waveforms can be generated.


  • ? mA +12V
  • ? mA -12V
  • ? mA 5V

This Module is discontinued.

submitted Jun 27th 2014, 15:11 by ringer | last Change Feb 22nd 2019, 08:04 by xtront

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