ADDAC 713 Stereo Discrete Mixer (2022–)

A compact stereo mixer that goes from clean summing to heavy distortion with a twist of a knob.

Overview

The ADDAC 713 Stereo Discrete Mixer is a black panel with modest knobs, eight HP wide. It looks quiet. Crank it and the whole system howls. It doesn't just blend signals, it colors them with the unpredictable saturation of a fully discrete analog circuit. It's inspired by the Moog CP3 mixer, and it is not a transparent utility module.

On paper it's practical. There are three stereo channels with individual gain and pan controls, plus a fourth mono channel for anchoring kicks or bass in the center. The real action is the feedback-driven overdrive circuit. Turn the feedback knob clockwise and the mix saturates, then distorts, then clips asymmetrically. At extreme settings it gates the signal entirely. That's by design. Increasing feedback shifts the audio bias upward until the waveform gets shoved off the rail and the sound cuts out completely.

The 713 isn't a one-trick box, though. With gain staging kept in check, it sums signals with clarity and warmth, so it works as a final output stage or a submixer for drum groups. The soft clipping switch has three positions: soft low-pass (tames transients and reduces clicks), off (full signal path), and hard low-pass (a more aggressive filter for smoothing out digital harshness). That helps when feeding sensitive downstream gear like converters or analog recorders.

Unlike op-amp-based designs, the 713 uses discrete transistors throughout. That gives it a grittier, more dynamic response. It reacts to input levels like a vintage console - push it and it pushes back, adding harmonics. It's particularly popular for drum and percussion work, where you can pan stereo sources while driving the mix into saturation. It also works as a final stage for a full system, where a touch of feedback can glue a patch together or send it into noise.

Specifications

Manufacturer	ADDAC System
Production Years	2022–
Original Price	220€ (assembled), 105€ (DIY kit)
Format	Eurorack
Width	8HP
Depth	40mm
Current Draw +12V	80mA
Current Draw -12V	80mA
Channels	3 stereo, 1 mono
Inputs	3 stereo pairs (6 total), 1 mono
Outputs	1 stereo master output
Gain Controls	4 per channel (extreme range)
Pan Controls	3 (for first three stereo channels)
Feedback/Gate Knob	1 (modulates overdrive and signal bias)
Master Output Knob	1
Soft Clipping Switch	3-position: Soft LPF / Off / Hard LPF
Signal Monitoring	2 LEDs (Left and Right output)
Circuit Type	Fully discrete analog (CP3-inspired)

Key Features

The Feedback That Gates

The feedback knob does more than create self-oscillation or mild saturation. As feedback increases, the circuit shifts the DC bias of the audio signal upward. At maximum, the waveform is lifted so far that it exceeds the voltage rail and the output is cut off. This "gate effect" is unpredictable but useful, especially when modulated. Patch an LFO or envelope into the feedback CV input (it's normalled but can be overridden) and you get rhythmic gating, stuttering, or rhythmic distortion sweeps. It's not a clean effect. It suits industrial, noise, or experimental work where control comes second.

Stereo Flexibility with a Mono Anchor

The channel layout is asymmetrical on purpose. Three stereo channels, each with its own pan, handle pads, effects, or stereo drum buses. A fourth mono channel stays center-anchored, for kick drums, bass oscillators, or anything you don't want drifting. That makes the 713 handy as a drum submixer: hi-hats, snares, and percussion go in the stereo field while the low end stays locked down. The pan controls are smooth and centered, with no dead zone. Each channel's gain goes well beyond unity, so you can overdrive individual sources before they hit the mix bus and layer the distortion.

Soft Clipping as Anti-Click Armor

The three-position soft clipping switch is small but useful. In "Soft LPF" mode, a gentle low-pass filter engages before the output, smoothing transients and reducing click artifacts, which helps when using the mixer to gate or modulate signals. "Hard LPF" applies a steeper roll-off and tames high-frequency harshness from digital oscillators or FM sources. In the center "Off" position, the full bandwidth passes through. Many users report cleaner integration with digital gear or converters when the soft clipping is engaged, since it avoids the brittle edge of fast transients in modular systems.

Historical Context

The Moog CP3 mixer never had a proper Eurorack heir, and the ADDAC 713 came out of that gap. The CP3, a rare and coveted module from Moog's early modular days, was known for a warm, slightly dirty character and a tendency to saturate nicely under load. ADDAC released the 703 Discrete Mixer, a mono version of this circuit, for users who wanted that CP3 sound in a modern format. The 713 expands the concept into stereo, responding to growing demand for spatial processing in modular systems. By 2022, when the 713 launched, Eurorack had moved past basic voice-building into complex, layered systems where stereo imaging and mix character mattered. Competitors like Manhattan Analog's DTM offered faithful CP3 clones. ADDAC took a different path, inspired by the original but evolved for contemporary use, with panning, stereo inputs, and expanded overdrive behavior.

It arrived during a wave of renewed interest in discrete analog circuits, as users tired of pristine digital mixers looked for gear with grit and response. The 713 wasn't the first stereo mixer with overdrive, but it was among the first to make distortion a central, modulatable feature. Its closest peers, like the Happy Nerding 4x St Mix or the Befaco Summer, offer different flavors of coloration, but none replicate the 713's bias-shift gating trick.

Collectibility & Value

The ADDAC 713 is still relatively new, but it has a cult following among noise, industrial, and experimental modular users. As of 2026, used units are scarce and prices stay close to new - typically €200 - €250 depending on condition and region. The DIY kit (€105) is more common on the used market. It requires intermediate soldering skills, since it's an SMD-assist kit with pre-soldered surface-mount components and through-hole parts to finish. The circuit is fully discrete and not microprocessor-controlled, so failure points are minimal. There's no firmware to die. The feedback circuit is sensitive, though, and poor gain staging can lead to constant clipping. Some users report this makes the module feel "always dirty" if it isn't dialed in carefully.

Owners note that the module demands care in patching. Overloading inputs or cranking the master without adjusting channel gains can lead to harsh distortion or even DC offset issues. It's not a set-and-forget mixer. When buying used, check that the feedback knob sweeps smoothly without crackling, and that the LEDs respond symmetrically to signal. Also verify the soft clipping switch clicks cleanly between positions. Some early units had flaky switches, though no widespread failures have been reported.

Given its unusual behavior and the lasting appeal of CP3-style circuits, the 713 is likely to hold value well. It's not a beginner's mixer. ADDAC doesn't overproduce, so scarcity keeps demand steady. If you see one in good condition under €220, grab it.