ADDAC 216 Dual Attenuverter and CV Processor ()
A black-paneled module that turns simple CV and audio signals into sums, differences, and absolute values.
Overview
The ADDAC 216 Dual Attenuverter and CV Processor is a Eurorack module from ADDAC's ADDAC200 Series. It's an 8hp black-panel unit, and it does a lot for its size. It's more than an attenuverter. It's two signal-processing channels where addition, subtraction, inversion, rectification, and offset are all on the panel. Think of it as vector math with voltages, minus the code.
The two identical sections, A and B, each start with a pair of inputs (X and Y) that can be summed or subtracted. Standard mixers only sum. Subtracting gives you a real-time difference between two control voltages or audio waveforms. After the sum-or-subtract stage, the signal hits a switchable full-wave rectifier labeled "Absolute," which flips all negative excursions positive. That tames bipolar LFOs or makes rectified audio textures. Then it passes through the "Amplitude" attenuverter, which scales the signal and can also flip its polarity.
Next comes the AC/DC coupling switch, which decides whether the signal keeps its DC offset or stays clean for audio use. After that is a bipolar Offset knob that shifts the whole signal up or down in voltage. Each section has a normal and an inverted output. The outputs from both sections are also summed and sent to a shared "Average" output, which can work as a passive mixer or collapse two complex modulations into one control source. With a single input, the module becomes a dual attenuverter and CV processor with rectification and coupling options.
The 216 suits patches that need precision and flexibility. Say you're deep in a generative sequence and need to invert, offset, and rectify a clock divider's output all at once. It handles both CV and audio. It doesn't generate signals, but it reshapes them with options that most mixers or attenuverters don't have.
Specifications
| Manufacturer | ADDAC |
| Product type | Eurorack module |
| Width | 8hp |
| Depth | 36 mm |
| Module Height (U) | 3U |
| Panel Colour | Black |
| Power consumption | 40mA +12V, 40mA -12V |
Key Features
Two Identical Signal Processors (Section A & B)
The ADDAC 216 is built around two mirrored sections, A and B, giving two independent processing paths. You can run identical processes in parallel, such as offsetting two LFOs by the same amount, or chain the sections for cascading voltage manipulation. Each section handles its own input pair (X and Y), runs the signal through the same series of stages, and delivers both normal and inverted outputs. That suits stereo patches, or controlling two parameters from the same base modulation with independent shaping.
Sum and Difference Mixing
Instead of only summing input signals like a conventional mixer, the 216 lets you add or subtract them. That's rare in utility modules. Feed two LFOs into X and Y and you get a new modulation waveform that's either their combined motion or the gap between them. At audio rate, the module acts as a phase-sensitive mixer where waveforms can cancel or reinforce each other.
Switchable Full Rectification ("Absolute")
After the sum/difference stage, the signal passes through a switchable full-wave rectifier labeled "Absolute." When engaged, it converts all negative voltages to positive, effectively folding the waveform. This turns bipolar modulation sources, like sine or triangle LFOs, into unipolar envelopes. It can also make distorted audio textures from clean waveforms. Each section toggles the rectifier on or off, so both the raw and rectified versions of a signal are always available.
Amplitude Attenuverter with Polarity Control
Following rectification, the signal hits the "Amplitude" stage. It's a true attenuverter that scales the signal from full negative to full positive, so you can reduce the level and invert the polarity at the same time. It's especially useful after subtraction or rectification, where you can flip the final output's direction or create negative feedback paths in modulation chains. Two LEDs per section monitor the output polarity and gain.
AC/DC Coupling and Bipolar Offset
Each section has an AC/DC coupling switch, which determines whether the output carries a DC offset (useful for CV) or has it stripped (ideal for audio). After coupling, a bipolar Offset knob shifts the entire signal up or down by a set voltage. That biases audio signals into the positive range, or moves the center point of an LFO so it modulates parameters asymmetrically.
Dual Outputs and Average Mix
Each section provides a normal and an inverted output, which doubles the available signals. This is handy for sending one modulation to several destinations with opposite polarities, such as one filter opening while another closes. The module also sums the outputs of both sections and routes them to a shared "Average" output. That combines two processed signals into a single control voltage, useful for master modulation sources or feedback loops.
Flexible Use as Dual Attenuverter & CV Processor
With only one input used per section (either X or Y), the 216 still works as a dual attenuverter and CV processor. The full signal path - rectification, amplitude control, coupling, and offset - stays available. It's two attenuverters with extra features in 8hp, which helps in smaller systems where every hp counts.
Collectibility & Value
The ADDAC 216 is currently available new at £139.00 including UK VAT, with an ex-VAT price of £90.83 (Elevator Sound). A Reverb listing shows $152.03 for a new unit, with the original launch price reportedly $181.59. So the module has either been discounted over time or varies by region and distributor. Given its specialized function and solid build, it holds value as a niche utility module rather than a collector's item. No data exists on common failures, maintenance needs, or long-term reliability, but its passive-heavy design and lack of sensitive components suggest it's likely sturdy.
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