Doepfer A-151 Quad Sequential Switch Manual (PDF)
The A-151 Quad Sequential Switch is not a sound source by itself — it’s a bi-directional 4-step sequential router. That makes it extremely powerful for rhythm design, because in modular percussion, routing is composition.
Every trigger at Trig In advances the switch to the next stage. Reset In forces it back to step 1. On version 2, the 2/3/4-step switch is especially useful for polyrhythms and odd cycles.
Think of the A-151 as a way to:
Because it is bi-directional, it works equally well as:
That means it can distribute gates, or select between CV/audio/modulation sources.
Patch:
Each incoming trigger advances to the next output, so one stream becomes a cycling voice allocator.
This creates instant interlocking rhythms from a single pulse train. If your incoming clock is steady 16ths, the voices will fire in rotation, producing a distributed pattern instead of a unison stack.
This is one of the easiest ways to get pseudo-African cross-rhythm, rotating accents, or IDM-style drum displacement.
Patch:
Now each accent pulse lands on a different destination in sequence.
Your percussion line becomes animated without needing a separate sequencer for every accent lane.
Send the outputs to: - kick decay CV - snare pitch envelope trigger - hi-hat accent VCA - clap filter ping
Now the same accent stream changes which parameter gets emphasized each hit.
This is excellent for dense but controlled variation.
Patch:
The A-151 will step through four trigger sources, deciding which pattern controls the drum voice at any given moment.
Use rhythm sources of different lengths: - pattern 1 = 5 steps - pattern 2 = 7 steps - pattern 3 = 8 steps - pattern 4 = 9 steps
Then clock the A-151 advancement independently from those patterns. The composite result takes a long time to repeat.
This is a powerful meta-sequencing trick.
If you have version 2, the 2/3/4 switch is gold.
Use one A-151 in 3-step mode while the rest of the system loops in 4, 8, or 16.
For example: - 16th-note clock into Trig In - O/I gets a trigger stream - outputs go to 3 drum destinations - A-151 set to 3 steps
Now the trigger rotates every 3 hits while your measure structure remains 4-based. This yields a repeating phase relationship over 12 pulses.
If you reset it only every few bars, the feel becomes even less square.
The Reset In is the key to complex time signatures.
By forcing the switch back to stage 1 before completing 4 steps, you can create:
Now the switching phrase cycles in a 7-pulse structure even though the module itself is 4-stage.
Reset at changing intervals: - 3 pulses - then 2 - then 3 This gives a 3+2+3 phrasing feel.
If you have logic, clock dividers, or trigger sequencers, this becomes extremely expressive.
Patch:
Now each hit gets a different modulation source.
This is where the A-151 becomes a variation machine.
Because the module can switch audio, use it to select among several raw sound sources before one shared VCA/filter/distortion chain.
Patch:
One percussion “voice” changes identity every hit or every phrase.
This is great for: - glitch percussion - machine-like drum mutation - making a small system sound much larger
Older versions handle a smaller signal range than v2. Version 2 supports the full A-100 range. If your module is older, keep audio/CV levels within the safe range described in the manual.
Send one fast trigger stream into the A-151 and route outputs to: - short noise ticks - filtered clicks - muted tom pings - ring-mod metallic taps
Then mix all four voices.
Because each sound only gets every fourth hit, the pattern becomes sparse per voice but dense as a whole. This is a classic way to get busy top-end percussion that still feels organized.
Use a second irregular trigger stream to reset the A-151, causing the voice order to restart unexpectedly.
Use the A-151 to route a burst generator or ratchet source to different drum voices.
Patch: - burst output -> O/I - outputs to different percussion triggers - another sequence/clock controls Trig In
Each burst lands on a different drum destination over time.
A single ratchet source becomes distributed fills: - kick stutters - snare rolls - hat flams - metallic glitches
This is especially effective in techno, jungle, breakcore, and experimental rhythm.
The manual explicitly mentions that very fast triggering can create audio-frequency modulation. This means the A-151 can act as a crude timbral combiner when switched fast enough.
The switching becomes so fast it creates a new composite timbre. For percussion, this can produce: - aggressive digital-like transients - tearing metallic hits - unusual pseudo-bitcrushed attacks - animated hybrid drum tones
Don’t use this as your whole drum tone all the time. Use it for: - attack layers - transient enhancement - occasional fills - industrial percussion accents
This gives a top layer that cycles every 3 hits against the bar.
The reset interrupts the natural 4-step order, creating a 5-pulse phrase contour.
Your snare pattern changes identity over the course of a phrase instead of just repeating.
Now the voice distribution lives in a 7/8 phrase.
Every hit changes the behavior of the sound source.
Use the A-151 to rotate: - different pitch envelopes - different decay CV amounts - different click layers - different trigger patterns
This gives kicks that alternate between: - short punch - long boom - hard transient - muted ghost hit
Rotate: - noise sources - filter settings - envelope shapes - trigger densities
This can make one snare voice behave like a full evolving snare section.
This is where the A-151 really shines. Rotate: - closed/open hat triggers - different decay CVs - different noise/filter combinations - accents - burst density
You get extremely articulate upper percussion with minimal modules.
Switch: - modulation index sources - oscillator relationships - trigger streams - waveforms
This creates animated clangorous rhythms perfect for industrial, electro, or broken beat.
Don’t think of reset as only “start over.” Use it as: - barline correction - phrase punctuation - fill generator - odd-meter enforcer - live improvisation control
A manual gate button into reset can be very powerful in performance.
This is one of the most important tricks.
If the trigger stream being switched is not the same as the clock advancing the switch, you get much richer behavior: - missed hits - shifted accents - phase patterns - long non-repeating structures
The A-151 becomes far more powerful when fed by: - clock dividers - Euclidean rhythms - logic outputs - Bernoulli gates - burst generators - trigger delays
These modules create the complexity; the A-151 distributes and reorganizes it.
Try: - fast triggers for local variation - slower trigger advancement for phrase movement - even slower resets for macro-structure
This gives nested rhythm: - hit level - beat level - bar level - phrase level
That is how you get genuinely complex percussion instead of mere randomness.
One ratchet source into O/I, outputs to 4 percussion voices, irregular clock on Trig In, reset every 11 or 13 pulses.
Four CV sources into I/O, O/I to drum pitch/decay/filter, step length set to 3, voice trigger in 4/4.
Four independent sequenced trigger patterns into I/O, O/I to one voice, switch advanced by a separate 5-step clock.
Four audio transients into I/O, fast oscillator clocks Trig In, O/I to distortion/VCA for brutal digital percussion.
The Doepfer A-151 is excellent for complex percussion, not because it generates rhythms by itself, but because it lets you reassign rhythmic function over time.
For dense, advanced rhythmic music, use it to:
In a percussion-focused rack, this module is basically a rhythmic router/composer.