ADDAC System 215 (2019–)

A 6HP Eurorack sample and hold that turns noise into melody and doesn't take much room doing it.

Overview

It's easy to overlook a module this small. It's 6HP, black anodized aluminum, with no flashy lights and no knobs begging to be twisted. But the ADDAC System 215 Dual S&H+ is a quiet workhorse. At its core, it's a dual sample & hold with a high-quality noise source. That undersells it, like calling a Swiss Army knife "a thing with a blade." It shapes randomness, distributes modulation, cross-patches control signals, and works as a basic analog computer with its sum, difference, and average outputs.

Sample & hold modules have a notorious flaw: voltage droop. Left alone, the sampled voltage slowly leaks away, and a steady pitch sags into a flat note. The 215 nearly eliminates this. Documentation cites a drift of just 0.01V over 20 minutes. You can sample a V/oct signal, hold it for an entire verse, and still have it land in tune. That stability makes generative sequences, transposed melodies, and voltage memory tricks workable where lesser modules would fail.

Each channel switches between Sample & Hold and Track & Hold modes. In Track & Hold, the input passes through while the trigger is high and freezes when it goes low. That suits smoothing chaotic signals or capturing moving voltages at precise moments. Each channel also has its own slew processor, with a single knob controlling both attack and decay, plus an on/off switch. So you can turn random voltages into gliding portamento or soft-edged control curves, all in the same module. The noise source is normalled to both inputs, so random CV starts with no patching. Just clock it.

Specifications

Manufacturer	ADDAC System
Production Years	2019–
Original Price	$175
Width	6 HP
Depth	40 mm
Current Draw +12V	50 mA
Current Draw -12V	50 mA
Channels	2
Sample & Hold Modes	Sample & Hold, Track & Hold
Clock Modes	Normal, Alternate (A/B flip-flop)
Slew Controls	Per channel, single knob for rise/fall
Noise Source	White noise, internal
Normalled Inputs	Noise to both S&H inputs
Additional Outputs	Noise, Difference (A–B), Average ((A+B)/2), Sum (A+B)
Trigger Input	Gate/trigger compatible
Signal Inputs	1 per channel
Signal Outputs	1 per channel, plus 4 shared outputs
Weight	120 g

Key Features

Smart Clocking and Signal Routing

The alternate clock mode lets a single trigger input toggle between channel A and B, which gives a round-robin distribution of random voltages. Patch it to two oscillators and each note alternates between voices. Route it to filter cutoffs and the modulation bounces between left and right. The logic mirrors the Buchla 266, and ADDAC clearly respects West Coast synthesis. Unlike the vintage gear, the 215 fits it into the Eurorack standard with no external logic required.

Sum, Difference, and Average – The Hidden Brain

Four extra outputs sit on the back: Noise, Difference, Average, and Sum. They make the 215 an active signal processor instead of a passive utility. The Sum and Average outputs blend control voltages, which works for morphing between two random sequences. The Difference output (A minus B) acts like a comparator, useful for opposing modulation or crude rectification effects when patched at audio rate. At audio speeds, this can generate octave-up tones or metallic textures. It's not a full wavefolder. These outputs let you build complex modulation networks without spending space on mixers or math modules.

Slew as a Creative Filter

The slew limiters are integral to the module. Each channel's slew can be engaged independently, so jagged random walks become smooth, evolving curves. Turn the knob down for slow, LFO-like undulations. Crank it and you're back to sharp, digital-seeming steps. Depending on the slew setting, the 215 can act like a gentle analog sequencer or a chaotic digital glitch source. Users report that the response is fast even at low settings, so musical results need careful adjustment.

Historical Context

The ADDAC System 215 arrived in late 2019. Eurorack had plenty of utility modules by then, but few were rethinking the classics. Sample & hold had become a commodity - cheap, often noisy, and prone to droop. The 215 treated randomness as a serious compositional element. Lisbon-based ADDAC, known for blending analog warmth with digital precision, positioned the 215 as a "hybrid" tool: analog in signal path, digital in logic, with firmware-level attention to voltage stability.

It landed between the minimalist utility ethos of Doepfer and the boutique complexity of Make Noise or Intellijel. The Doepfer A-148 offers dual S&H in 8HP but no slew or math outputs, so the 215 packs more functionality into less space. It also avoids the "kitchen sink" approach of modules like the ALM Busy Circuits SEQ-3, and focuses on refinement over raw feature count.

Collectibility & Value

The ADDAC 215 isn't rare. It's still in production and widely available, so it has none of the cult status of discontinued modules. On the used market, expect to pay $100 - $130 for a working unit, down from the original $175. Prices stay moderate because supply is steady and demand is practical.

Failures are rare, and when they happen, it's usually power-related. The module draws 50mA on both rails, which is modest, but owners report that reversed power cables can damage the PCB. No field failures are widely documented, but service technicians note that the SMD components, while robust, aren't user-replaceable without skill. If buying used, test all outputs. The sum, difference, and average functions can fail silently if a trace is broken. Also check the slew response. Some early units had inconsistent potentiometer wear, though this seems to have been resolved in later runs.

For DIY builders, a kit version exists (SMD-Kit-2), rated "easy/medium" difficulty. It includes both surface-mount and through-hole parts, so beginners may struggle. For those who complete it, the build quality rivals the pre-assembled version. Given the low failure rate, most collectors prefer pre-built units unless cost is a major factor.