Module A-154 is a supplement to the A-155 Analog / Trigger Sequencer module. It offers a lot of new features that are not available in the basic control unit of the A-155. The A-154 is used to replace the control unit of one or two A-155, i.e. the section marked "Control" with Start / Stop / Step / Reset buttons and inputs in the upper left corner of the A-155 front panel. If the A-154 is used to control the A-155 the control section of the A-155 is put out of action.

These are the features of the A-154:

Several running modes: forward, backward, pendulum, random, CV controlled step addressing. All modes are available as loop or one-shot.

LED display of the 5 different current modes and one LED for loop / one-shot display

Manual and voltage controlled selection (with attenuator) of the running mode. If no external control voltage is applied one of the 10 modes (5 modes x 2 loop / one-shot) is simply selected with a rotary knob. The CV input with attenuator is used to modulate the running mode with an external control voltage (digital high / low CV to switch between two modes or continuous analogue CV to sweep through different modes). With the combination of manual control and CV with attenuator it is possible e.g. to use only two neighbouring modes (e.g. forward / backward) or sweep through all possible running modes

Manual and voltage controlled selection (with attenuator) of first and last step of the sequence. The range is step 1...8 in 8 step mode resp. 1...16 in 16 step mode

If the running mode "CV Controlled Step Address" is selected the First Step section is used to determine the active sequencer step. Consequently manual and voltage controlled selection (with attenuator) of the active step is possible: the active step can be set by hand with the first step manual control and then modulated by an external control voltage (e.g. LFO, Random, S&H, Theremin, Light CV source, Joy Stick) at the first step CV input (with attenuator).

An internal voltage controlled clock generator with manual and CV control (with attenuator) is available. The output of the clock generator is displayed with a LED and is used as sequencer clock provided that no external clock signal is connected to the Clock In socket (normalled socket). If the CV input of the Clock section is connected to one of the analogue outputs of the sequencer the time for each step can be set separately. Even jumps (or skipping) will be possible as we will introduce the feature that a very short clock pulse will be generated if the control voltage exceeds a certain value. For example the gate row of the A-155 can be used to obtain skipping of steps: the gate output simply has to be connected to the CV input of the A-154 clock generator. If the corresponding switch of the A-155 is set correspondingly in the gate row the step will be skipped.

Manual and voltage controlled (with attenuator) pulse width (PW) of the clock signal. This features can be used to obtain a different gate length for each step: e.g. one of the CV outputs of the A-155 can be used to control the PW. With a PW control voltage coming from a LFO / random / S&H the gate length will change automatically. CV coming from Theremin A-178, ribbon controller A-198, light controlled CV A-179, joy stick A-174 are other ways to control the gate length.

8 / 16 step mode: A toggle switch us used to select 8 or 16 steps. The "16 step" mode requires two A-155 and one or more voltage controlled switches (e.g. A-150-1 or A-150-8). The voltage controlled switches are controlled by the "A3" output of the A-154. This output remains "low" as long as the active step is in the range 1...8 and turns to "high" in the range 9...16. The voltage controlled switches are used to switch between the CV / trigger / gates outputs of the first A-155 (step 1...8) and the second A-155 (step 9...16). In the A-154 user's manual the corresponding patch is shown.

If two A-155 are used they can work in parallel (8 steps) or serial (16 steps). The 8 / 16 steps switch determines if the 8 step mode (one A-155 or two A-155 in parallel) or the 16 step mode (two A-155 serial) is chosen. Both modes work with CV controlled step addressing too (see below). In 8 step mode only the steps 1...8 are addressed, in 16 step mode the steps 1...16. For serial operation an additional VC switch (A-150) is required - as mentioned above.