ADDAC System ADDAC308 Light to CV ()

It doesn't make sound. It turns flickers and shadows into voltage for your modular.

Overview

The ADDAC308 Light to CV isn't a voice, an oscillator or an envelope. It's a translator. It reads light and outputs control voltage. It's part of ADDAC System's 300-series Expressive Controls, a 4hp Eurorack module that turns ambient shifts, hand shadows or flashlight sweeps into CV that can modulate pitch, filter cutoff, panning, or anything else with a CV input.

The light sensor connects through a standard 3.5mm jack, so you can place it outside your rack - on a table, taped to a wall, or mounted on a moving object. The sensor is enclosed in a jack socket, so it's rugged and patch-cable-ready. Inside the module, an LED and LDR (light-dependent resistor) are housed in patch cable-compatible enclosures, which makes it easy to build custom light paths or feedback loops. You could patch the module's output to a VCA controlling an external light source pointed back at the sensor. That gives you a self-modulating system that pulses on its own.

Owners report using it in subtle ways, nudging parameters just enough to feel alive, like a slow sunrise opening a filter over three minutes. Others use hand motions to warp textures in real time. One user described using it to "alter different aspects of Mutable Instruments Elements" in a nuanced, evolving patch. Another shared a video where the ADDAC308 controls both Elements and Rings.

It's not a module for stacking fat leads. It's the one you reach for when you want your synth to respond to the room.

Specifications

Manufacturer	ADDAC System
Width	4hp
Depth	4.5cm
Power consumption	±50mA
Outputs	2 Bipolar CV Streams (Output and Inverted Output)
Controls	Sensitivity, Response (3 fixed settings: medium/fast/slow), Gain, Offset, Inverted Offset
External sensor	enclosed in a jack socket
Features	The module includes an LED and LDR (light-dependent resistor) housed in patch cable compatible housings.

Key Features

Light to Voltage Translation

The ADDAC308 converts incoming light into control voltage. More light hitting the sensor gives a higher CV output on the main output. The inverted output does the opposite: more light, lower voltage. That gives you both polarities without needing an inverter module. You can open a filter with increasing brightness or drop a pitch as a shadow passes, and the response is immediate.

External Sensor with Flexible Placement

The light sensor connects via a standard 3.5mm mono cable, so it isn't confined to your rack. You can dangle it over your synth case, tape it to a lamp, or hide it under a translucent surface on your desk. Put your hand above the sensor to swell a drone, or use a rotating gobo for rhythmic modulation. The jack-socket housing makes the sensor durable and easy to build into a permanent setup.

Dual Outputs with Independent Offset

You get two CV streams: one normal, one inverted. Each has its own offset control - Offset for the main output, Inverted Offset for the second. You can bias each output to sit in a specific voltage range, say 0-5V for a VCO pitch input or -2.5V to +2.5V for a wavetable position. The Gain knob sets the overall amplitude for both outputs, so you can scale the response to match your system.

Response Switch for Slew Control

The Response control is a switch with three fixed settings: slow, medium, and fast. It applies slew to the raw light signal and smooths out abrupt changes. Set to slow, it turns quick hand motions into gentle swells, which suits ambient textures. Fast mode tracks rapid changes, useful for rhythmic or percussive modulation. It isn't a continuously variable slew, but the three-step design keeps the module simple.

Sensitivity Adjustment for Low-Light Use

The Sensitivity knob adjusts how responsive the sensor is to light levels. Turn it up and the module reacts even in dim rooms, which suits studio use where you might not want a spotlight on your rack. In bright conditions, dial it back to prevent clipping or overmodulation.

LED and LDR in Patchable Housings

Besides the external sensor, the module has an internal LED and LDR, each housed in patch cable-compatible enclosures. This lets you build closed-loop systems. Patch a CV source to the LED input, drive it with an LFO, and let it shine on the LDR to generate a secondary CV. You can also build opto-isolated feedback paths, where light, not electricity, carries the signal.