ADDAC 304 (2010s)

Eight gate buttons in an 8HP frame. Half of them also work as momentary signal pass-throughs, and the other half are pure manual triggers.

Overview

The ADDAC 304 doesn't make a sound and won't generate a sequence. What it does is let you play the modular instead of just patching it. Each button has a rubbery, positive action and sends out a +5V gate. There are no menus, no screens and no MIDI latency, just eight physical triggers. Use them to fire envelopes, advance sequencers or hit a sample trigger.

Four of the eight channels double as momentary signal pass-throughs. Plug a CV or gate into one of those inputs and press the matching button. Instead of a fixed +5V, the module passes the incoming signal through, and only while the button is held. That makes the 304 a manual gate processor. You can hold a button to let a slow LFO move your filter at one moment in a performance, or trigger a modulation chain with your finger instead of a clock.

Designed as part of ADDAC’s 300 series—focused on expressive, performance-oriented controls—the 304 fits neatly into the brand’s philosophy of blending utility with physical interaction. It’s not trying to be a brain; it’s the nervous system’s fingertips. The build is solid, typical of ADDAC’s no-nonsense Eurorack aesthetic: black or red anodized aluminum panel, cleanly labeled, no wasted space. At just 25mm deep, it tucks into even the most packed skiff or travel case without issue. And while it draws a trivial 10mA from the +12V rail (nothing from -12V or +5V), its impact on a patch is disproportionately large. It’s the module you reach for when you want to break out of the cycle of “patch, press play, adjust, repeat” and start performing—when you want to turn your modular setup from a laboratory into a stage instrument.

Specifications

Manufacturer	ADDAC System
Production Years	2010s
Original Price	€90 (assembled), €58 (DIY kit, excl. VAT)
Format	Eurorack
Width	8 HP
Depth	25 mm
Current Draw +12V	10 mA
Current Draw -12V	0 mA
Current Draw +5V	0 mA
Gate Output	0 to +5 V
CV Input Range	±10 V
Button Type	Momentary switches
Channels	8 manual gates
Momentary Pass-Through Channels	4 (channels with inputs)
Power Connector	8-pin IDC (Doepfer style)
DIY Availability	Yes, SMD and through-hole kit

Key Features

A Split Personality: Trigger + Gate

The ADDAC 304’s standout feature isn’t just having eight buttons—it’s that half of them are smarter than they look. The first four channels (those with input jacks) don’t just output a static +5V gate; they act as momentary gates for whatever signal you patch into them. This means you can route a complex CV sequence, an LFO, or even an audio-rate pulse into one of these inputs, then use the button as a manual gate to let it through only when pressed. It’s like having four manual VCA gates built into a trigger panel. Want to bring in a stutter effect only during a solo? Patch a clock into input 2, press the button in time. Need to manually inject a modulation sweep at a dramatic moment? Route your envelope follower here and fire it by hand. It’s a small feature that opens up huge performance possibilities, turning passive modules into interactive ones.

Tactile, Reliable Switching

In a world of touch plates, ribbon controllers, and capacitive sensors, the 304’s physical momentary buttons feel refreshingly honest. They have a soft rubber dome under each cap, offering a satisfying tactile bump with a short travel—enough feedback to know you’ve triggered it, but not so much that it slows down rapid tapping. They’re not clicky like arcade buttons, nor mushy like some membrane switches; they strike a balance that works for both deliberate, dramatic triggers and quicker rhythmic patterns. And because they’re momentary, the gate only fires while the button is held—perfect for controlling gates that need variable duration, like percussive hits or filter sweeps. The panel layout is clean and logical, with inputs on the left, outputs on the right, and clear numbering. No guesswork, no hunting—just press and go.

DIY-Friendly Design

True to ADDAC's roots in the DIY synth community, the 304 is available as a full build-it-yourself kit, with SMD and through-hole components. The assembly guide is well documented and the board layout is straightforward, which makes it a solid intermediate-level project. The kit includes the PCB, front panel, jacks, buttons and all components, so there's no scavenging required. Panel swaps or custom modifications, like adding LEDs or changing button colors, are possible. The current draw is low and the circuit is passive, essentially just switches and protection diodes. Soldering errors are unlikely to do damage, assuming you test for shorts first.

Historical Context

The ADDAC 304 emerged in the early 2010s, as Eurorack was shifting from a niche hobbyist curiosity to a legitimate performance platform. Modules were getting more complex and more digital. Performers found themselves staring at sequencers, tweaking parameters on touch interfaces, or relying on external MIDI controllers. The 304 went the other way, back to physical, immediate control. It did one thing, manual triggering, and added a clever twist.

At the time, dedicated manual gate modules were rare. Most performers relied on spare buttons on MIDI controllers, or reached into their racks to press a cable into a jack. The 304 filled that gap with a purpose-built design. It wasn't the first button-based module, but it was among the first to integrate pass-through functionality. Competitors like Intellijel's Push 2 or Make Noise's Pressure Points offered more features, like pressure sensitivity or CV output. They were also larger, more expensive, and often overkill for simple triggering needs. The 304 was the small, affordable, no-frills option.

ADDAC was releasing a mix of hybrid digital-analog modules and performance-focused utilities during this period. The 304 fit into that lineup as a tool for musicians who wanted to keep their hands on the music instead of buried in menus. It also reflected a broader trend in modular design, the rise of "utility" modules that weren't sound generators or processors but aids to performing and patching.

Collectibility & Value

The ADDAC 304 isn't rare, but it isn't exactly common either. It's been in steady production for over a decade, available both assembled and as a DIY kit, so finding one on the used market isn't difficult. It doesn't get churned through the secondhand circuit often, though. Once someone adds it to their system, they tend to keep it. Used prices typically range from $80 to $120, depending on condition and whether it's assembled or a kit. Assembled units in good condition with no panel scratches or loose jacks tend to sit around $100 - $110, while DIY kits sell for $60 - $80.

Failure points are minimal, which is part of the 304’s appeal. There are no active components on the board—just switches, jacks, and protection circuitry—so there’s little to go wrong. The most common issue reported is a stuck or unresponsive button, usually due to debris under the cap or a failed switch. These are easy to fix: pop off the button cap, clean the switch, or replace it entirely. Jacks can loosen over time, especially with frequent plugging and unplugging, but a quick solder touch-up resolves that. Because the module draws no power from the -12V or +5V rails, power-related failures are nonexistent.

When buying used, check that all eight buttons actuate cleanly and return fully. Test each output with a multimeter or connected module to confirm it’s sending +5V when pressed. If it’s a DIY unit, ask whether it was built correctly—though given the simplicity of the circuit, even a novice build is likely to work if it powers up without shorts. Custom panel versions (available in green, blue, white, bronze, etc.) are slightly more desirable and may command a small premium, but they’re mostly cosmetic. The real value is in functionality: a working 304 is worth every penny in a live rig.