4-string Eurorack synthesizer with humbucker pickups - 122HP case
ADDAC120HS is the compact version of ADDAC System’s Strings Humbucker system, housed in a 122HP unit. It integrates a headstock and bridge, humbucker pickups, robotic picks, automated mute, and rotary exciter in a more compact format than the 197HP version, while still offering a fully functional stringed instrument that can be played, processed, and controlled via CV, trigger, or MIDI—ready for use in your modular system.
The ADDAC120 forms the physical foundation of the system—a Headstock & Bridge module that accommodates strings with gauges up to .055. The strings are installed exactly as on a guitar: the user is free to choose their preferred set of strings and tuning. The headstock is equipped with 4 locking tuners to make string installation faster and easier; the string holes can also be enlarged to accommodate thicker strings.
The set includes a Bow Arch Attachment, which raises the two center strings so a bow can reach each string individually, and Small Resonators, which are simple yet extremely effective at adding harmonics to the unwound strings. Each resonator applied generates a new partial: by adding more, the timbre becomes progressively more complex, resulting in sounds reminiscent of a bell.
The ADDAC121 is the system’s humbucker pickup module, equipped with Tone and Volume controls and a LOW/HIGH gain switch to add saturation to the signal. A built-in preamp boosts the volume to synth levels. The pickup’s height is adjustable via the mounting screws, and it can also be removed for manual use.
The ADDAC124 features a servo motor for each string, allowing you to pluck them independently via dedicated buttons, input triggers, or MIDI. In Pluck mode, the servo moves approximately 20 degrees for a full pluck; in Harmonic mode, the movement is reduced to about 10 degrees, lightly touching the string to bring out harmonics—by positioning the module at the midpoint, 2/3, or 3/4 of the string’s length. Up to 3 modules can be daisy-chained to pluck and generate multiple harmonics simultaneously. Twelve replacement picks are included.
Four 3-position switches control the module’s behavior: the top position disables the trigger and MIDI inputs, leaving only the buttons active; the middle position activates Pluck mode with all inputs active; the bottom position activates Harmonic mode, also with all inputs active. The height of the picks is adjustable via screws—lower for Pluck mode and raised by approximately 4 mm for Harmonic mode.
Inspired by the Mute system found on some Fender Jaguar and Bass VI guitars, the ADDAC125 uses a servo motor to raise and lower a sponge that, when pressed against the strings, slightly dampens their natural vibration, producing a tone different from a traditional palm mute. The module is passive and must be connected to an ADDAC124 Plectrums, either by replacing one of its servos or by operating in parallel using the dedicated splitter cable. For maximum effectiveness, it should be positioned as close as possible to the headstock.
The Rotary Exciter features a 7,000 RPM brushless motor that rotates a surface equipped with four oppositely polarized magnets, generating a rotating magnetic field. When the rotation speed matches the fundamental frequency or harmonics of a string, the string is forced to vibrate, creating sonic textures that would otherwise be impossible to achieve manually. A Speed knob and a CV input allow for nonlinear control of the motor speed.
Technical Specifications
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