A-155 Analog/Trigger Sequencer

The A-155 Analog / Trigger Sequencer is a well-equipped 2 x 8 step sequencer with three trigger tracks, one gate track and two control voltage tracks.

Triggers 1 and 2 are always alternative, as are trigger 3 and the gate signal. Separate settings for “glide” (portamento) can be made for the two control voltages.

In addition, the module can also be used as a luxurious 8:1 switch via the “External CV/Audio Inputs” – both for control voltages and for audio signals.

User interface










Switching between the two tracks (16 steps)

If the 8 steps are not enough, you can – even without the A-154 – switch between the two control voltage tracks. To do this, the clock signal is split up and sent to an A-160-1 frequency divider (which is way cheaper than the A-154). Here we use the “/8” division to toggle using an A-150-1 switch.

Attention: since the frequency divider “counts up”, i.e. it outputs a gate signal at the 8th step, switches it off again at the 16th step, etc. we first get an asynchronous behavior to the sequencer: The sequencer should actually be switched to the 9th step (instead of the 8th), to the 17th (instead of the 16th), etc. A manual reset of the A-160-1 frequency divider can help here (the reset should be done in step 2 of the A-155).

Oscillator, filter and envelopes controlled by the sequencer

The upper control voltage track is very well suited for controlling the pitch of VCOs, as it can be easily switched between 1, 2 and 4 octaves. In addition, you can e.g. modulate the cutoff-frequency with the lower control voltage track.

“Trig 1” could control an A-140. For special accents, “Trig 2” triggers a second A-140 (with different settings), which also controls VCA and VCF. This allows accents to be generated that go far beyond a mere “louder”, as other sequencers allow. In order to set these accents, simply select “Trig 2” with the toggle switch of this step instead of “Trig 1”.

Two A-140s are controlled by the A-155. The first is for “normal” tones, the second ADSR generator can be used with a different envelope setting for special accents.

Useful supplements

Although the basic version of the A-155 offers a wide range of options, far more complex sequences can be implemented in combination with the A-154 Sequencer Controller. With its help you can, for example, combine two A-155s into a 4-track sequencer or (with an additional A-150-1 switch) into a 16-step sequencer.

Another useful add-on module for tonal sequences is the A-156 Dual Quantizer, which can limit the output voltages of the sequencer to semitone steps or major/minor scales.

Technical specifications

Width50 HP
Depth40 mm
Power requirements80 mA (+12V) / -20 mA (-12V)