Behringer – Abacus – Music Computer

The Behringer Abacus — officially titled the ABACUS Analog Music Computer — is one of the most talked-about budget entries in the Eurorack ecosystem. Released around 2023 (with widespread availability continuing into 2025–2026), this 20 HP module democratizes extremely powerful function generation and voltage processing that was previously locked behind much higher price points.

At its core, the Abacus is a close clone/reinterpretation of the iconic Make Noise Maths (particularly v2), while also nodding to the foundational Buchla 257 (voltage processor) and 281 (quad function generator) modules from the late 1960s/early 1970s West Coast tradition.

Why “Music Computer”?

Behringer chose the name “Analog Music Computer” deliberately — the module performs true analog computational operations on control voltages:

• Addition / subtraction
• Attenuation / inversion
• Integration (slew / portamento / lag)
• Differentiation-like behavior in envelopes
• Multiplication-like scaling via response curves
• Logical OR combinations (via end-of-cycle outputs)

These aren’t just modulation sources; they’re voltage algebra tools that let you derive new signals from existing ones in musically expressive ways.

Key Technical Specifications

• Format: Eurorack, 20 HP width, ~24 mm depth
• Power: +12 V: 60 mA, -12 V: 50 mA, +5 V: 0 mA
• Function channels: Effectively two full function generators (channels 1 & 4 are the most featured), plus supporting logic
• Time range — envelopes / LFOs from ~25 minutes per cycle to ~1 kHz audio-rate oscillation
• Curve shapes: Continuously variable from logarithmic → linear → exponential (via Response / Both knobs)
• Inputs per main channel (1 and 4):
• Signal / CV input
• Trigger / Gate input
• CV control over Rise / Attack time
• CV control over Fall / Decay time
• Outputs per channel:
• Main signal output (0–8 V typical envelope range)
• End of Attack / End of Rise gate (channel 1)
• End of Cycle / End of Fall gate (channel 4)
• Mixer / processor section:
• 4-channel bipolar mixer/attenuverter (channels 1–4)
• Sum, inverted Sum, OR logic outputs
• Cycle / Loop mode: Independent per channel (self-oscillating LFO behavior)
• LED indicators: Activity / state per channel

Architecture Breakdown

The Abacus is best understood as having three main functional blocks:

1. Dual Core Function Generators (Ch 1 & Ch 4)
   These are the heart — classic AD/ADR/AHD-style slope generators with voltage-controlled attack & decay times.

• Trigger a gate → rise to peak (attack) → fall back (decay)
• In cycle mode → continuous LFO (triangle, ramp, saw depending on rise/fall balance and curve)
• Response knob morphs the curve shape dramatically — very Buchla-like
• At audio rates they become surprisingly decent (for analog) VC(LF)O sources

1. Channel 2 & 3 — Supporting Processors
   These act as additional attenuverters / mixers with some slew capability, feeding into the main sum bus.
2. Central Mixer & Logic

• Bipolar mixing of all four channels + external signals
• OR output produces a gate whenever any channel finishes its cycle (great for chaotic sequencing)
• Inverted sum is perfect for negative excursions or mirror modulation

Typical Use Cases

Here are some of the most common (and creative) patches people build with the Abacus:

• Dual complex envelopes — one percussive, one swelling pad shape
• Voltage-controlled LFOs with voltage-controllable rate and shape
• Slew limiter / portamento on pitch CV (classic use)
• Envelope following + offset + inversion
• Chaotic / chaotic clock divider using OR logic + feedback
• Audio-rate wavefolder-ish timbres (cycle fast + modulate response)
• Tempo ramping — modulate rise/fall times with another slow LFO for accelerando/ritardando effects
• Logic-based sequencing — OR multiple gates to create pseudo-random or polymetric triggers

Comparison: Abacus vs. Make Noise Maths v2

Feature	Behringer Abacus	Make Noise Maths v2	Notes
Width	20 HP	20 HP	Identical
Current draw	~60/50 mA	~60/30 mA	Very similar
Build quality	Solid surface-mount	Through-hole premium	Abacus feels surprisingly good
Knobs / feel	Smooth pots	Very high-quality	Subjective, but close
LED brightness / style	Bright	Subtle	Personal taste
Street price (2026)	$60–100	$280–330	Massive savings
“Official” inspiration	Buchla 257/281	Buchla + own design	Abacus leans harder into Buchla
Community perception	“Good enough Maths”	The original	Abacus wins on value

Many users report that — once calibrated and warmed up — the Abacus tracks and behaves remarkably close to Maths for 90–95% of patches, especially envelopes and LFOs.

Final Thoughts

The Behringer Abacus isn’t trying to be subtle — it’s a loud, proud statement that “mathematical analog voltage processing shouldn’t cost $300+.” Whether you’re new to modular and want the “Maths experience” without the price tag, or you’re deep in a system and want a second (or third) function generator that won’t break the bank, the Abacus delivers.

In 2026 it remains one of the highest “features-per-dollar” modules available in Eurorack.

If you’re building a small skiff or just want more modulation madness without compromise, few modules punch as far above their weight class as this little analog music computer.

Have you patched with the Abacus yet? What’s your favorite unexpected use? Drop it in the comments.

Happy patching.