ADDAC 815 (2022–)

A compact stereo mixer that colors the signal with a little analog warmth. It suits minimalist Eurorack builds.

Overview

The ADDAC 815 is easy to overlook. It's just 6HP wide, with no flashy knobs and no modulation inputs. Plug it in and it does one thing well: it glues a mix together. It's an active, discrete, class-A stereo mixer, and when driven it adds a faintly creamy saturation. Born from ADDAC's "Mixology" series, it's one of the most space-efficient stereo mixers in the Eurorack world. It's the module to reach for when you want to avoid digital summing but don't have room for a full-sized console-style mixer.

Many compact mixers cut corners with op-amps or digital summing. The 815 uses discrete transistor circuitry derived from the same design language as ADDAC's 712 Vintage Pre and 713 Stereo Discrete Mixer. That gives it real gain staging, real headroom and real harmonic texture when you push it. Each of the two stereo channels has two inputs with dedicated level controls, and the summed output goes through a final master level knob. There are no VCAs, no panning and no effects. It's clean, warm, analog summing with a slight forward presence in the upper mids that helps synths cut through without harshness.

And while it doesn’t scream “vintage” like a tape emulator or saturating preamp, the 815 earns its place by being the quiet foundation that makes everything else sound better. It’s not a special effect—it’s infrastructure. Think of it as the difference between a well-constructed wooden table and a folding plastic one: both hold your gear, but one feels like it belongs in the system.

Specifications

Manufacturer	ADDAC System
Production Years	2022–
Original Price	€160
HP	6
Depth	40mm
Current Draw +12V	80mA
Current Draw -12V	40mA
Inputs	4 (2 stereo channels, each with 2 inputs)
Outputs	1 stereo output (3.5mm)
Input Impedance	100kΩ
Output Impedance	600Ω
Topology	Discrete class-A amplifier
Gain Structure	Fixed gain per channel with master output level
Signal Path	Fully analog, DC-coupled
Bypass	No
Module Type	Mixer, Attenuator Modules
Weight	180g
Panel Color	Black anodized aluminum with white silkscreen

Key Features

Discrete Class-A Signal Path

The ADDAC 815 doesn't rely on off-the-shelf op-amps for its summing. It uses a discrete transistor amplifier design that mirrors the topology found in high-end studio gear from the 1970s. Service technicians note that the circuit layout and component selection closely follow classic discrete preamp designs known for their linearity and low distortion at nominal levels. When driven, the 815 introduces second-order harmonics in a gentle, musical way, never fuzzy or harsh. That subtle saturation helps blend complex FM patches or gritty wavefolders into a cohesive stereo image, acting like a mini analog bus compressor without actually compressing.

Stereo Channel Architecture

Each of the two stereo channels accepts two signals and sums them internally before feeding into the master output stage. The left input of each channel is normalled to the right, so you can run mono sources into the left jack and get a centered image. The per-channel level knobs are smooth and precise, with a logarithmic taper that makes fine adjustments easy. The channels are fully independent, so you can group related modules - say, all your drum voices on channel A and melodic elements on channel B - then balance them with the master output.

Compact Build, Full Signal Integrity

At only 6HP, the 815 is one of the most space-efficient active stereo mixers in Eurorack. The 40mm depth is standard for ADDAC modules and fits comfortably in most cases, even shallow ones. The build is consistent with the brand's reputation: thick aluminum panel, sturdy jacks and a clean PCB layout. Unlike some budget mixers that suffer from crosstalk or ground noise when densely packed, the 815 keeps a quiet noise floor and solid channel separation. Documentation shows that ADDAC paid particular attention to grounding and power filtering, likely informed by user feedback on earlier mixer designs. It feels substantial for its size.

Historical Context

The ADDAC 815 arrived in 2022, as Eurorack was shifting away from maximalist, feature-heavy modules and toward focused, high-quality utility tools. Many manufacturers were cramming more CV control, digital processing and patch memory into mixers. ADDAC went the opposite direction. The 815 is a direct descendant of the 713 Stereo Discrete Mixer, stripped of extras like individual output jacks and gain trimmers. It isn't trying to be a mixing console. It's a small-format analog summing stage.

The modular community has grown to appreciate "invisible" processing - tools that enhance sound without drawing attention to themselves. The 815 sits alongside modules like the Intellijel Quad VCA and the Mutable Instruments Yarns in that category. It also reflects ADDAC's Lisbon-based design ethos, which blends Portuguese craftsmanship with a deep respect for vintage signal flow. It isn't based on a single historical device like the 712 or 714, but its circuit is clearly informed by the same lineage of 1970s discrete console design that inspired those modules.

Competitors at the time included the Doepfer A-138m and the ALM O/A Mix. Both offer more channels or VCAs, but with less analog character. The 815 doesn't win on features. It wins on tone.

Collectibility & Value

As of 2026, the ADDAC 815 is still in production and readily available new from dealers like Thomann and Perfect Circuit, typically priced around $170-$180. Used units appear occasionally on the secondhand market, trading for $120-$150 depending on condition. It's a modern module with stable supply, so it's not a speculative collectible. It has developed a quiet reputation among minimalists and touring musicians who value reliability and sonic quality in a small footprint.

Failures are rare. The discrete circuitry is robust, and there are no delicate trimmers or microcontrollers to fail. The most common issue reported by technicians is jack wear from frequent plugging and unplugging. The jacks are standard Switchcraft-style and easy to replace. No firmware updates or calibration are required. Because it's DC-coupled, it can pass control voltages, though users should not exceed ±12V, as the output stage isn't designed for high-level CV signals.

When buying used, check for consistent output levels between channels and listen for any crackling in the knobs, which could indicate dust in the potentiometers. A quick test with a sine wave into both channels should reveal any imbalance or distortion. Given its simplicity, the 815 is one of the lowest-maintenance modules in a Eurorack system. There's almost nothing to go wrong, and what little can is fixable with basic soldering skills.