Doepfer A-151 Quad Sequential Switch Manual (PDF)
The A-151 is a 4-step bidirectional sequential switch: each trigger advances the common jack to the next of four jacks, and reset returns it to step 1. In v2, you also get a 2/3/4-step selector and full ±12V signal handling. Practically, it can behave as:
Because it is so simple, it becomes powerful when paired with clocks, gates, envelopes, VCAs, mixers, sequential voltage sources, logic, and sound sources.
Key takeaways from the manual:
That means the A-151 is not just a utility switch — it is a structure generator.
If you want the A-151 to shine, pair it with:
What to patch - VCO triangle/saw/pulse/sub into I/O 1–4 - O/I to filter or VCA - Clock the Trig In with LFO, gate pattern, or another VCO square
Result - Slow clocks: stepped timbral changes - Medium clocks: rhythmic waveform alternation - Audio-rate clocks: new buzzy composite timbres, crude wavefolding-ish textures
Make it better - Put slightly different processing on each waveform before the A-151: - one dry - one filtered - one wavefolded - one ring modded - Then switch between “versions” of the same oscillator.
Recommended partners - Any analog VCO - Wavefolder like uFold / A-137 - Filter with strong character - Fast square LFO or oscillator for triggering
What to patch - Sequencer CV or modulation source into O/I - Outputs I/O 1–4 to: - VCO pitch - filter cutoff CV input - waveshaper amount - effect parameter
Clock the A-151 to rotate where the same CV goes.
Result A single melodic or modulation pattern gets “thrown” around the patch, creating animated arrangements from minimal material.
Variation Use different attenuators on each destination so the same source behaves differently each step.
Great with - precision adders - attenuverters - quantizers - modulation destinations that like stepped CV
This is one of the manual’s examples and it’s genuinely excellent.
What to patch - Four envelopes into I/O 1–4 - O/I to filter CV, VCA CV, wavefolder CV, or FM index CV - Same clock/gate triggers all four envelopes and also clocks the A-151
Result Each note uses a different envelope shape, even though the voice architecture stays the same.
Best use - Different filter plucks per step - Different VCA dynamics - Alternating long/short accents - Different FM index shapes for each note
Upgrade idea Use: - one AD envelope - one slow AR envelope - one snappy exponential envelope - one looping envelope
Now the timbre cycles in a more performative way.
Reverse the prior idea.
What to patch - A single envelope into O/I - I/O 1–4 to various CV destinations: - filter - VCA - oscillator PWM - FX send level
Result On each trigger, the envelope shapes a different aspect of the patch. This can make one voice feel like a whole arrangement.
Try Routing one envelope sequentially to: 1. pitch sweep 2. filter ping 3. reverb amount 4. wavefolder depth
What to patch - Voice or drum loop into O/I - I/O 1–4 each go to a separate processor input path - Return processed outputs to mixer
Or, depending on your routing options, feed: - four different processed versions of a sound into I/O 1–4 - take O/I as the selected result
Example four paths - dry - delay - phaser - distortion
Result Per-step FX changes without needing a full matrix mixer.
Best with - compact stereo mixer - FX aid / Mimeophon / Magneto / Desmodus style processors - drum voices or drones
Also suggested by the manual.
What to patch - Use a multi-mode filter with several simultaneous outputs: - LP - BP - HP - notch - Patch those to I/O 1–4 - O/I goes to VCA/output - Advance A-151 every note or every bar
Result The same source walks through different filter characters.
Why it works This keeps pitch/melody stable while changing the spectral role of the sound. Very useful in techno, electro, and generative patches.
Great companion filters - Doepfer A-121 - Mutable Ripples - QPAS - any SEM-style or multimode filter
The reset input is where a lot of the musical magic lives.
What to patch - Steady clock to Trig In - A different rhythm or gate pattern to Res. In
Result Instead of a boring 1-2-3-4 loop, you get asymmetrical forms: - 1-2-1-2-3-1-2-3-4... - 1-2-3-1-2-3... - irregular restarts synced to another pattern
Creative sources for reset - gate from sequencer end-of-cycle - Euclidean rhythm - manual gate button - comparator output from slow CV - odd clock division
Very effective for - melody selection - timbral phrase resets - structured but non-repetitive modulation
If you have v2, use the step selector musically.
Patch idea - Run one A-151 at 3 steps - Another sequential process elsewhere at 4 or 5 steps - Clock both together
Result Longer evolving cycles due to pattern interference.
With one A-151 Even just switching the module between 2, 3, and 4 steps during a performance changes perceived phrase length instantly.
Use for - drum fills - bass variation - call/response structures - modulation loops that never line up the same way twice
What to patch - Main pitch CV sequence into O/I - Outputs I/O 1–4 to four precision adders or quantizer input chains, each with a different offset/transposition - Or reverse it: put four different transposed versions into I/O 1–4 and take O/I to the oscillator
Result Same melody, different harmonic positions each step/bar.
Examples - root - +5th - octave - minor 3rd
Excellent with - quantizer - precision adder - buffered multiple - chord-capable oscillators
What to patch - One trigger stream into O/I - Outputs I/O 1–4 to four drum trigger inputs
Now each incoming trigger hits a different drum in sequence.
Result A single pulse train becomes a pattern spread over kick/snare/hat/clap or multiple voices.
Variation Send irregular triggers to the A-151 clock, and a master pulse stream through the switched path, or vice versa.
Advanced variation Route accent CV instead of triggers so different drums get the same accent pattern on different steps.
What to patch - Accent gate or accent envelope into O/I - I/O 1–4 to: - VCA CV boost - filter accent - FM amount accent - delay feedback duck/accent path
Result Each accent lands on a different musical parameter, which gives far more life than a static accent lane.
The A-151 is not a divider itself, but it can behave like a rotating clock destination.
What to patch - Master trigger into O/I - I/O 1–4 to four envelope gates, drum triggers, or sequencer advance inputs - Clock A-151 with a slower pulse
Result A repeating trigger source gets sent to different modules over time, creating changing rhythmic emphasis.
Companion modules - clock dividers - Bernoulli gates - trigger delays - logic modules
This is especially good in drum systems.
What to patch - Four modulation sources into I/O 1–4: - slow sine LFO - random stepped CV - looping envelope - sample & hold - O/I to one destination like filter cutoff
Result That one destination behaves like it has a “macro arrangement” around it, with each section animated differently.
Best destination choices - filter cutoff - wavetable position - wavefolder depth - stereo spread - reverb size
Excellent for experimental patches.
What to patch - Put the A-151 in a feedback network: - mixer send or processor output into O/I - I/O 1–4 go to different feedback treatments: - clean feedback - filtered feedback - distorted feedback - delayed feedback - Selected path returns to mixer/effect input
Result Feedback character changes step by step. This can create very alive dub-techno and noise textures.
Be careful Levels can get intense quickly; a VCA or attenuator in the feedback loop helps a lot.
What to patch - Four CV sources into I/O 1–4 - O/I to sample & hold input - A-151 clocked slowly, S&H clocked faster or differently
Result The S&H draws from a rotating set of source voltages, producing much more structured random-ish behavior.
Example sources - offset voltage - sequencer row - noise through slew - envelope - slow LFO
Great with - quantizer for melodies - slew for glide - comparator for rhythm extraction
What to patch - Four related audio signals into I/O 1–4 - same oscillator through 4 filters - four phase-shifted signals - four harmonic-rich sources - Clock A-151 from oscillator square or another audio-rate source
Result Harsh, digital-like spectral animation; metallic tones; animated drones.
Especially good with - fixed filter banks - phase shifters - ring mod - submixes of harmonics
What to patch - Pitch CV can be multed to several voices - Gate into O/I - I/O 1–4 to four envelope/gate inputs for four voices
Clock the A-151 with the same keyboard gate, or a derived trigger.
Result Each new note is assigned to the next voice, creating rotating pseudo-polyphony or layered variation.
Useful with - multiple identical voices - chord stacks - per-step different timbres
Use the A-151 not on the final sound path, but on the control path feeding another modulator.
What to patch - Four CV sources into I/O 1–4 - O/I to FM amount CV, LFO rate CV, envelope decay CV, or clock rate CV
Result You’re changing the behavior of another modulator in steps, which creates deeper evolving systems.
Example Route 4 voltages to your LFO rate input: - very slow - medium - fast - near audio
Now your filter modulation “changes gears” each phrase.
If you have multiple short sequencers or 4-step voltage rows:
What to patch - Four 4-step sequencer rows or voltage memories into I/O 1–4 - O/I to oscillator pitch or filter CV - Advance A-151 every 4 notes using a clock divider
Result You effectively chain four short sequences into a longer form.
Excellent modules for this - Pressure Points - A-155 rows - Voltage Block channels - 0-CTRL rows - simple voltage sources plus attenuators
Create four different complete versions of a sound or control idea, then use the A-151 to move through them.
Example scene sources 1. dry bass 2. filtered bass 3. FM bass 4. delayed bass
or in CV terms: 1. calm modulation 2. rhythmic modulation 3. random modulation 4. extreme modulation
The A-151 gives clean scene changes with a simple clock.
This turns the A-151 into a phrase and structure machine.
Very fertile for self-running patches.
This keeps melodies coherent while still changing.
This creates “composed” irregularity.
Use the A-151 to select different sources or destinations, then use the matrix mixer to blend the consequences. Great for performance systems.
Two A-151s together are much more than double the power: - one selects pitch source - the other selects timbre source - different clocks/reset patterns create long cycles
Or chain them to make more than 4 stages.
Patch a button or gate controller to Res. In.
During performance, force the cycle back to step 1 to re-anchor the phrase.
On v2, move between: - 2-step for tight alternation - 3-step for lopsided groove - 4-step for full phrase
It’s a simple but very effective performance gesture.
Send a shared modulation or effects send sequentially to different voices. Each bar, a different voice gets the spotlight.
You get a bassline that sounds arranged rather than looped.
Simple, elegant macro-evolution.
Small patch, big groove payoff.
Excellent for ambient, industrial, and electroacoustic work.
This makes a single sequence feel alive immediately.
The Doepfer A-151 is deceptively powerful. It excels at:
If you treat it as a compositional router rather than just a utility switch, it becomes one of the most musical low-HP modules in Eurorack.