Doepfer — A-151 Quad Sequential Switch

Manual PDF

Doepfer A-151 Quad Sequential Switch — Cheat Sheet

What it does

The A-151 is a 4-step sequential switch: each trigger advances the connection between the common jack and the next one of 4 switched jacks.

Think of it as an electronic rotary switch for: - 4 inputs → 1 output, or - 1 input → 4 outputs

It is bi-directional, so either use case works.

Core behavior

Each rising edge at Trigger In advances to the next step.
Steps cycle:
1 → 2 → 3 → 4 → 1
Reset In immediately returns the switch to step 1.
LEDs 1–4 show the active step.
Version 2 modules add a 2/3/4 step selector.

Controls / Indicators

LEDs

LED 1–4: show which I/O 1–4 is currently connected to the common jack.

Switch

Steps switch (Version 2 only):
2 = alternate between I/O 1 and 2
3 = cycle through I/O 1–3
4 = full 4-step cycle

Jack Reference

Inputs

Trig. In
Function: advances the switch one step on each rising edge
Type: trigger input
Voltage range: not explicitly stated for trigger threshold in the manual
Res. In
Function: resets immediately to I/O 1 on rising edge
Type: reset input
Voltage range: not explicitly stated for reset threshold in the manual

Common jack

O/I
Function: common output/input
Connects to the currently active I/O 1–4
Signal direction is patch-dependent
Voltage range:
- Version 1: -8 V to +8 V
- Version 2: -12 V to +12 V

Switched jacks

I/O 1
I/O 2
I/O 3
I/O 4

Each is a bidirectional switched jack connected in sequence to O/I.

Voltage range for all I/O jacks: - Version 1: -8 V to +8 V - Version 2: -12 V to +12 V

How to patch it

1) Switch between 4 signal sources

Patch: - 4 different signals into I/O 1–4 - Take output from O/I - Send clock/triggers to Trig. In

Result: - Each trigger selects the next source.

Good for: - Oscillator waveform switching - Selecting different modulation sources - Switching among filter outputs

2) Send 1 signal to 4 destinations

Patch: - Signal into O/I - Destinations from I/O 1–4 - Clock into Trig. In

Result: - One source is routed to a different destination each step.

Good for: - Sending one CV to different modulation targets - Distributing gates or modulation in sequence

3) Shorter repeating sequences

Use either: - Version 2 Steps switch to set 2, 3, or 4 steps, or - Reset In to force return to step 1

Example: - With reset timing, you can create 1 → 2 → 3 → 1...

Musical uses from the manual

Waveform sequencing: switch between VCO waveform outputs
Audio-rate switching: very fast triggering can create new timbres / audio-rate modulation effects
Envelope sequencing: cycle through different envelopes affecting a filter
Filter mode stepping: switch among multimode filter outputs per note

Important notes / gotchas

The module is bi-directional: there is no fixed “input side” vs “output side” for the audio/CV path.
On Version 1, signals outside -8 V to +8 V may cause malfunction.
Version 2 supports the full A-100 signal range: -12 V to +12 V.
Very fast triggers can push the switch into audio-rate behavior, which can be creatively useful.

Quick reference

Element	Type	Function	Voltage Range
Trig. In	Input	Advance one step on rising edge	Not specified
Res. In	Input	Reset to step 1 on rising edge	Not specified
O/I	Bidirectional jack	Common jack connected to active step	V1: -8 to +8 V, V2: -12 to +12 V
I/O 1	Bidirectional jack	Step 1 jack	V1: -8 to +8 V, V2: -12 to +12 V
I/O 2	Bidirectional jack	Step 2 jack	V1: -8 to +8 V, V2: -12 to +12 V
I/O 3	Bidirectional jack	Step 3 jack	V1: -8 to +8 V, V2: -12 to +12 V
I/O 4	Bidirectional jack	Step 4 jack	V1: -8 to +8 V, V2: -12 to +12 V
LED 1–4	Indicator	Show active step	—
Steps switch	Toggle/selector	Limit cycle to 2, 3, or 4 steps	Version 2 only

In one sentence

Use the A-151 whenever you want a clocked, resettable way to cycle one signal through 4 destinations or cycle through 4 sources into one destination.

Generated With Eurorack Processor