ADDAC300 Series ()

When your feet, muscles, or motors need to talk to your modular, this is how they do it.

Overview

The ADDAC300 Series isn’t about oscillators, filters, or envelopes. It’s about control — the kind that doesn’t come from a keyboard or sequencer, but from your body, your pedals, or even a tiny motor turning a knob while you watch. Made by ADDAC System, these Eurorack modules fall under the banner of “300’s Expressive Controls,” a lineup dedicated to expanding how you interact with your synth. These aren’t sound generators; they’re translators, turning physical gestures into voltages, movements into modulation, tension into triggers. If your hands are already full patching, twisting, or playing, the ADDAC300 Series gives the rest of you something to do.

This is a family of modules designed for the tactile, the performative, the slightly theatrical side of modular synthesis. Whether it’s reading the flex of a muscle, the press of a foot, or the slow sweep of a servo-driven knob, these units thrive on real-time expression. They’re not essential in the way a VCO is, but they’re unforgettable in a live set. And while they share a series name and design philosophy, each module serves a wildly different purpose — from the utilitarian (dual attenuators and switchers) to the experimental (muscle sensing) to the downright mischievous (power starvation). Together, they form a toolkit for anyone who wants their synth to respond to more than just notes.

Specifications

Key Features

ADDAC301 & Floor Control: Feet on the Controls

The ADDAC301 and its sibling the ADDAC301 Floor Control are essentially the same idea — a Eurorack module that lets you plug in standard sustain and TRS expression pedals. It’s a simple concept, but executed with thoughtful detail. You can fine-tune the expression pedal’s action using Range and Offset knobs: Range sets the voltage span from -10V to +10V, while Offset shifts that entire range up or down by ±5V. That means you can map a pedal’s travel to exactly the CV range you need, whether it’s sweeping a filter from 3V to 7V or modulating an LFO from -5V to 0V. Two LEDs show the positive and inverted CV outputs in real time, and the sustain input generates a gate signal, also LED-monitored. It even includes a +5V bus board adaptor, with a jumper on the back to enable it — a small but useful touch for systems that need that rail.

ADDAC301B & 301C: Passive Simplicity

The ADDAC301B Dual Expression Attenuator and ADDAC301C Dual Sustain Switcher take a no-power approach. Both are passive modules, meaning they don’t draw current from the power rail — just patch cables and physical control. The 301B lets you run any CV or audio signal through it and attenuate the level with an expression pedal. There’s even an invert switch, so pushing the pedal can decrease the signal instead of increasing it. The 301C does the same for on/off control: plug in a clock or audio source, stomp the pedal, and you’ve got a switchable gate or mute. At just 3 cm deep and 4 HP wide, they’re compact solutions for adding foot control without eating up power or space.

ADDAC303 Muscle Sensing: Control From Within

This is where things get weird — in the best way. The ADDAC303 Muscle Sensing module uses electrodes (included) to detect muscle tension, turning flexes and twitches into control voltages. The Gain knob adjusts the output range (±10V), while Offset sets the baseline (±10V). A Smooth switch lets you choose between hard and soft smoothing of the raw signal — useful for taming jittery readings. It outputs both a positive and inverted CV, plus a comparator gate with an adjustable threshold, so you can trigger events when muscle activity crosses a certain level. As one forum user put it, “Mmmm, muscle sensing. Wire me up.” It’s not just a gimmick; it’s a legitimate way to bring bio-responsive control into modular, and it’s about as direct a link between body and synth as you can get.

ADDAC306 VC Transitions: Five Channels of Morphing CV

The ADDAC306 VC Transitions is a five-channel CV generator that lets you morph between voltage states in multiple directions. Each channel has MINIMUM, SPAN, and DIRECTION controls, plus a common CV input and a shared TRANSITION CONTROLLER slider. You can set each channel’s max range to either 5V or 10V via jumpers on the back. The CV inputs accept up to +5V, and outputs are jumper-selectable between +5V or +10V. Only positive voltages are output, making it ideal for controlling parameters that don’t need bipolar modulation. It’s a powerful tool for evolving textures — think slow sweeps across filter cutoffs, wavefolds, or panning — all driven by a single control voltage.

ADDAC300 REV.02: Starve It to Make It Sing

Power starvation isn’t new — it’s a staple of circuit bending, where reducing voltage to an analog module can make it “cough, choke, go spastic,” as ADDAC puts it. The ADDAC300 REV.02 turns that hack into a safe, controllable module. It takes +12V from your power rail and uses a DC-DC converter to generate a bipolar 15V supply, which then passes through variable analog voltage regulators. The output voltage can be adjusted from 2.5V to 13.5V, with up to ±200mA available. The module itself can draw up to 600mA on the +12V rail, depending on the load. It includes short-circuit and overcurrent protection, so you won’t fry your synth trying to make it scream. This isn’t for modules that need stable power — it’s for the ones you want to misbehave in interesting ways.

ADDAC320 Servo Control: Motorized Knob Twisting

Inspired by Neil Young’s Whizzer, the ADDAC320 Servo Control uses a 270-degree servo motor to physically turn a knob on another module. A microcontroller reads incoming CV (0 to +5V) and converts it linearly to motor position. A spring wire and metal couplers connect the motor shaft to the target knob. Two front-panel knobs — MIN ANGLE and MAX ANGLE — let you define the “sweet spot” of travel, so you’re not spinning the knob past its useful range. If you raise MIN above MAX, the motion inverts. It’s a delightfully analog way to automate a parameter without patching a CV — just set it and watch the knob turn. Replacement servos are available for 6€ each, plus VAT, so if one burns out, it’s not a death sentence.

Historical Context

The ADDAC300 Series emerged from practical needs and playful experimentation. The ADDAC301 was born while the company was developing VC Stompboxes and testing expression pedals — they realized feet were often free during modular performances, and expression pedals were common, so why not bring that control into the rack? The ADDAC320 Servo Control pays homage to the “geniality” of Neil Young’s Whizzer, a motorized device that tweaks guitar effects mid-performance. And the ADDAC303 Muscle Sensing module was framed as introducing a “totally new interaction principle,” pushing beyond traditional controllers into bio-responsive territory. All these modules are grouped under the “300’s Expressive Controls” category, a clear signal that ADDAC System sees them not as utilities, but as tools for performance and expression.

eBay Listings

As an eBay Partner, we earn from qualifying purchases. This helps support our independent vintage technology research.

Related Models

• ADDAC300 REV.02
• 4ms Ping
• ADC 27
• 2hp LPG V2
• ALM AXON-2
• AMS DMX 2000
• Marantz SD-930
• Accuphase A-60
• Accuphase AC-1
• Accuphase DP-100