ADDAC System has announced a new module family that brings physical strings into Eurorack: the "ADDAC120s Four Strings Series." What follows is the ADDAC System press release.
- ADDAC120s Four Strings Series
- Concept and Development Background
- Additional Modules and Sonic Nuances
- Attachments for Performance Style and Playing Flexibility
- Module Specifications
- Closing Statement
- ADDAC120s Four Strings Series
ADDAC120s Four Strings Series
ADDAC System Announces its Four Strings Series, Opening Up String Centric Performance Canvas for Electronic Musicians
New family of string-based modules and tools inspire exploration and new methods of sonic expression in the world of modular synthesis
Lisbon, Portugal — June 17, 2026 — ADDAC System announces a "string revolution" in Eurorack synthesis: the Four Strings Series. Made up of an entirely new family of tactile modules, the Four Strings Series is designed as an open canvas that invites users to explore and engage with physical strings from a variety of perspectives, encouraging creative experimentation. The Four Strings Series begins shipping in July.
Concept and Development Background
The concept for the Four Strings Series grew out of the desire to bring physical strings — like those of a lap steel guitar or a dulcimer — into Eurorack. It was conceived to integrate seamlessly into any Eurorack frame. There is no fretboard, however, and despite a few constraints, the design allows other modules to be placed beneath the strings.
The headstock and bridge were developed first, letting the strings pass over the top so that other modules could sit underneath. Next came a humbucker module to pick up the sound of the strings, just like on a regular electric guitar. The limitations of a standard humbucker led to the development of a custom quadraphonic pickup with an independent pickup for each string, enabling independent volume control per string.
Additional Modules and Sonic Nuances
The team then moved on to exploring mechanical automation, developing a plectrum module that plucks each string independently. In parallel, a mute module was also developed. It dampens the natural vibration of the strings, mechanically automating the kind of behavior you get from a Fender mute or a palm mute on a guitar.
Other modules were explored over time. One of them is the rotary exciter, which generates a rotating magnetic field to excite a string whose frequency matches the motor's rotation speed. Another module, the Ebow slider, was also developed, using a harness and a slide mechanism to create an Ebow effect over any string.
Attachments for Performance Style and Playing Flexibility
Along the way to creating this new family of modules, a number of handy attachments were also developed. One of them is the headstock arch that mounts onto the headstock. It raises the two middle strings so that a bow can access each string individually. In addition, small plastic resonators were developed. Attached to the strings, they produce harmonics that closely resemble complex, bell-like tones.
And finally, an entirely new 122HP frame was built to house all of these modules, allowing the whole system to operate independently. By building a dedicated power supply into the frame, any residual noise the motors might generate is kept out of the system. The system can also be incorporated as a DIY build project, letting you create your own alternative to the frame.
Module Specifications
ADDAC120 Headstock & Bridge
This is the Headstock & Bridge module, the foundation of the string module range, supporting string gauges up to 0.055. Enlarging the holes lets you fit thicker strings. Both panels use 2mm-thick stainless steel for strength. The headstock features a set of four locking tuners that make installing the strings easier.
The Headstock & Bridge also comes with a bow arch attachment and a set of small resonators. The bow arch attachment raises the two middle strings so a bow can reach each string individually.
ADDAC121 Humbucker
This is a simple humbucker pickup module. It has TONE and VOLUME controls plus a LOW/HIGH gain switch for saturation. A built-in preamp brings the volume up to synth level. The pickup height can be adjusted with the mounting screws. The pickup can also be removed and held in your hand for use.
ADDAC122 Quadraphonic Pickup
This is a quadraphonic pickup with four independent pickups, each with its own preamp, independent VOLUME control, and output jack. A post-volume MONO MIX output is also provided. All outputs are at synth level. The pickup height can be adjusted with the mounting screws.
Because each string can be captured independently, four-channel routing is possible. It uses a hand-wound stacked humbucker construction with Alnico 5 slugs and 20,000 turns of 44AWG polyurethane wire, for roughly 7.4kΩ per coil.
ADDAC124 Plectrums
This is a plectrum module with a servo for each string, letting you pluck each string independently via dedicated push buttons, incoming triggers, or MIDI. In pluck mode, the servo moves about 20 degrees to effectively pluck the string. In harmonic mode, the servo moves only about 10 degrees and stops at the vertical position, lightly tapping the string to produce harmonics.
The per-string switch has three positions: up disables the trigger and MIDI inputs, middle is pluck mode with all inputs enabled, and down is harmonic mode with all inputs enabled. Holding any push button for more than two seconds enters calibration mode, where you can offset the plectrum position in 2-degree steps for precise adjustment. You can also combine multiple Plectrums modules and, by setting up different playing styles across the three switch-selectable modes, generate dynamics and harmonics.
ADDAC125 Strings Mute
This module is inspired by the Fender mute system found on some Jaguar and Bass VI guitars. The Fender version presses foam against the strings to dampen their natural vibration. This module uses a servo motor to raise and lower the foam, lightly dampening the strings' natural vibration when pressed against them. It is not as effective as a standard palm mute, but it lets you automate a different tone.
To use this module, you need to connect the servo to the ADDAC124 Plectrums module. You can either remove and replace one of the plectrum's servos, or use the included splitter cable to connect them in parallel, running both the plectrum and the mute at the same time.
ADDAC126 Rotary Exciter
This module features a 7000 RPM brushless motor that spins a face fitted with four magnets of alternating polarity. This creates a rotating magnetic field that forces a string to vibrate when the rotation speed matches the frequency of one of the strings' tuning or its harmonics.
A SPEED knob and CV input give you nonlinear control over the rotation speed.
ADDAC127 Ebow Slider
This module creates a harness and slide mechanism for a standard Ebow. It lets the user slide the Ebow back and forth beneath the strings. The Ebow used has a "PianoBow" modification, where the Ebow's legs are filed off so that it can sit closer to the string as it slides back and forth without making contact. The Ebow height can be adjusted up and down with four thumbscrews.
Bow Arch Attachment
This attachment raises the two middle strings so that a bow can reach each string individually.
Small Resonators
Very simple, but remarkably effective at adding harmonics to unwound strings. Each resonator attached to a string adds one new partial, and the more you attach, the more harmonics you get and the more complex the tone becomes. The tuning of each harmonic is determined by the resonator's position along the string. The resulting sound can be quite surprising, closely resembling bell-like tones.
ADDAC120F Strings Frame
This is a custom-built frame designed specifically for the ADDAC12X string modules.
The frame is designed to house all of the Four Strings Series modules, but it can also be used to power any additional modules you'd like to incorporate into the system.
The frame specifications are as follows:
90–240V AC plug with fuse drawer (2 fuses: 1 fitted + 1 spare)
122HP
+12V 1.5A
-12V 1.5A
+5V 0.5A (derived from +12V)
Closing Statement
Every product in the Four Strings Series is now available. We invite you to join the "string revolution" in Eurorack synthesis. For more details on each module and frame, including specifications and signal flow diagrams, visit the ADDAC System website.
ADDAC120s Four Strings Series
The Four Strings series is available both as individual modules and as bundle systems. Our shop carries only the frameless ADDAC120BS Strings Basic System. If you'd like a larger setup, please consider adding other modules from the series separately.
Modules / Frames
A matched pair of Headstock (17HP) and Bridge (6HP) panels with 4 locking tuners for easy string installation. Passive stainless-steel construction raises strings high enough to fit other modules underneath. Includes a string set (.010–.046), bow arch attachment, and small resonators.
A 10HP humbucker pickup module with an integrated pre-amplifier delivering synth-level output. Features TONE and VOLUME knobs plus a LOW/HIGH gain switch. Height-adjustable via mounting screws; the pickup can be removed for handheld use.
A 14HP quadraphonic pickup with 4 independent coils — one per string — each with its own pre-amplifier, VOLUME knob, and output jack (STRING 1–4), plus a MONO MIX output. All coils are hand-wound with Alnico 5 slugs, 44AWG polyurethane wire, and ~7.4kΩ per coil.
A 14HP plectrum module with one servo per string, triggerable via push-button, gate, or MIDI (USB + TRS). Offers Pluck mode (~20° swing to pluck the string) and Harmonic mode (~10° tap for harmonics). Up to 3 units can be daisy-chained.
A 10HP servo-driven mute module inspired by the Fender Mute (Jaguar/Bass VI). A foam pad lowers onto the strings to create a gentle dampening — a distinct tonal character different from palm muting. Passive module; controlled by an ADDAC124 Plectrums servo.
A 10HP module with a 7,000 RPM brushless motor spinning 4 magnets. When the motor RPM matches a string's resonant frequency or harmonics, the rotating magnetic field excites the string — similar to using a bow on an electric guitar. Speed is controlled by a SPEED knob and CV input.
A 16HP mechanical harness and sliding rail for a standard Ebow. The included Ebow is modified with the "PianoBow" mod (feet sanded down) so it slides freely below all strings without contact. Height is adjustable via thumb screws. Passive module; no power required.
Four Strings Systems (Bundles)
The ADDAC120BS Strings Basic System we carry is the entry configuration of the Four Strings series, bundling three modules: the ADDAC120 Headstock & Bridge that anchors and mounts the strings, the ADDAC121 Humbucker that picks up the strings' vibration as audio, and the ADDAC126 Rotary Exciter that physically excites the strings to produce sustained tones. The dedicated 122HP frame (ADDAC120F) is not included, so it is meant to be installed into your own Eurorack case and power supply. Start with this basic system as the minimum setup needed to "sound the strings," then add other series modules — the ADDAC122 Quadraphonic Pickup, ADDAC124 Plectrums, ADDAC125 Strings Mute, and ADDAC127 Ebow Slider — as you go, gradually widening your performance style and sound-design options.
About ADDAC System
ADDAC System is a modular synthesizer maker based in Portugal.
Their lineup is built on solid, no-nonsense modules that make the most of analog character. At the same time, they have released plenty of inventive modules that bring digital technology into the mix in a tasteful way — flexible CV-to-MIDI converters, deeply controllable granular processors, and more.
This was our introduction to the ADDAC120s Four Strings Series, announced by ADDAC System.
It's a quite experimental series — bringing the strings themselves into Eurorack and approaching them through multiple modules: pickups, plectrums, a rotary exciter, and an Ebow. Personally, I find it a genuinely exciting instrument. I hope you'll check out the intro video and more!