ADDAC System 701 (2012–2019, Rev2: 2019–2023)

Name: ADDAC System 701
Brand: ADDAC System

A plain analog oscillator that holds its tuning and still has some life in it.

Overview

Plug in the ADDAC System 701 and there are no flashy lights and no digital tricks. You get a thick, steady sine wave. It's an analog circuit built to track like a metronome, with the warm, slightly unpredictable sound analog fans want. Early adopters in 2012 found a module that felt like it came out of a late-'70s ARP or Moog system, with tuning stability those engineers would have envied. It isn't trying to be exotic. It's trying to be right, and it mostly succeeds.

The original 701 was built around the CEM3340 VCO chip, which powered classic synths from the Sequential Circuits Prophet-5 to the Oberheim Xpander. ADDAC didn't reinvent it. They built it cleanly, with high-quality components and a front panel layout that keeps the controls within easy reach. You get coarse and fine tuning knobs, a six-position octave switch (rare in Eurorack at the time), and a 1V/Oct input that tracks across a claimed seven octaves with good accuracy. The waveform outputs are sine, triangle, sawtooth and pulse, each with its own jack. That means you can route multiple waveforms from a single oscillator without mults or giving up headroom.

In 2019, ADDAC revisited the design with the 701 Rev2 and went after one of the original's few real weaknesses: long-term tuning drift. The Rev2 swapped in CoolAudio's modern reissue of the CEM3340, a chip that mimics the original's behavior with tighter tolerances and better thermal stability. They also refined the triangle-to-sine conversion circuit, which in the original could sometimes introduce slight artifacts under heavy modulation. The Rev2 tracks better and gives a cleaner sine wave, which matters for FM or for a pristine sub oscillator source. Owners report that it holds pitch through temperature swings that would send lesser oscillators into wobble, so it suits live use and complex patches.

Specifications

Manufacturer	ADDAC System
Production Years	2012–2019 (Original), 2019–2023 (Rev2)
Original Price	€450 (Original), €158 (Rev2 kit), ~$173 (Rev2 assembled)
Format	Eurorack
Width	8 HP
Depth	35 mm
Power Consumption	60 mA (+12 V), 60 mA (-12 V)
Oscillator Type	Analog VCO (CEM3340 / CoolAudio CEM3340)
Control Voltage Input	1 V/Oct
Frequency Range	6 octaves (coarse), 12 semitones (fine)
Octave Range	6 positions (switchable)
FM Input	Linear FM with attenuator
Sync Input	Switchable hard/soft sync
PWM Input	Pulse width modulation with attenuator
Waveform Outputs	Sine, Triangle, Sawtooth, Pulse, Mixed
Mix Section	3-knob mixer (SIN/TRI, MIX, SAW/RECT)
LFO Mode	Switchable VCO/LFO mode
Weight	~200 g (assembled)

Key Features

Onboard Waveform Mixing – A Rare Practical Touch

Most oscillators give you separate waveform outputs and leave the blending to your mixer. The 701 includes a three-knob mix section that blends sine and triangle, blends sawtooth and pulse, then crossfades between those two pairs. You can build hybrid waves on the fly, moving from a soft sine-triangle blend to a gritty saw-pulse stack with a single knob. Some users lament that the mix isn't CV-controllable, which would have allowed dynamic waveshaping, but the manual control is still powerful. It helps when you're layering in a filter or external processor and want to set the harmonic content before it hits the next stage. It's a feature more common in digital oscillators, and here it's pure analog.

Octave Switching with Real Utility

Most Eurorack oscillators rely solely on coarse frequency knobs, so the 701's six-position octave switch stands out. You can jump octaves without overshooting your target, and the click of a switch makes tuning multiple oscillators in unison easier. No more guessing whether you're a semitone high. The switch covers six octaves. Some users noted that the original had two unmarked positions beyond the labeled range, functionally repeating the top octave, but it was still more precise than twisting a knob. The Rev2 retained this design.

LFO Mode with Caveats

The 701 includes a VCO/LFO toggle switch, which drops the oscillator into low-frequency modulation duty. That frees up space in your rack. Early Rev2 units had a quirk, though: the octave switch didn't behave the same in LFO mode as it did in VCO mode, which caused tuning inconsistencies with sequencers. Some owners reported drift or unexpected frequency jumps when patched into clocked modulation sources. ADDAC acknowledged the issue and corrected it in later production runs by changing a capacitor value. If you're buying used, check for this, especially if you plan to use the module heavily for modulation. Later Rev2 units and all post-fix modules don't show this behavior.

Historical Context

The ADDAC 701 arrived in 2012, as Eurorack was shifting from niche curiosity to full-blown synth renaissance. At the time, many modules were either minimalist utility designs or over-engineered digital designs. The 701 was neither. It was a focused analog oscillator that put tuning stability and sound quality first. It wasn't the most feature-packed or the most experimental. It filled a gap: a reliable, Moog-style VCO that could sit in a modern rack without constant recalibration.

It competed directly with the Doepfer A-110-1 and the Intellijel Dixie, both of which also used the CEM3340 or its variants. The A-110-1 was barebones and the Dixie added extras like a sub oscillator. The 701 went after buyers with superior build quality and a thoughtful layout. ADDAC, a Portuguese company with roots in hybrid analog-digital systems, positioned the 701 as part of their "Analog Heritage" line, modules based on classic circuit designs and updated for modern reliability. The 701 wasn't a clone, but it shared DNA with the oscillators that defined the golden age of analog synthesis. It was also one of the few Eurorack VCOs at the time to include both octave switching and onboard waveform mixing, features that felt more at home on a vintage ARP or Oberheim than in a 3U case.

By 2019, the market had changed. Behringer's clones had driven prices down, and many users expected more features for less money. ADDAC responded with the Rev2, slashing the price dramatically, especially in kit form, and streamlining production. The shift from a premium boutique module to an accessible workhorse reflected broader trends in Eurorack, where reliability and value were becoming as important as rarity.

Collectibility & Value

The original ADDAC 701 is now a collector's item, with used prices hovering between $300 and $450 depending on condition and provenance. These early units are prized for their build quality and historical significance. They come from a time when Eurorack was still boutique. They have flaws, though. Some original units suffer from tuning instability over long sessions, especially with temperature fluctuations. Owners report that recalibration is occasionally needed, and spare CEM3340 chips are getting harder to source. If you're buying one, test it across multiple octaves and with sustained play to make sure it holds pitch.

The Rev2 is still relatively common and sells for $150 - $200 used. As a kit, it was priced at just €158, making it one of the most affordable high-quality analog VCOs ever made. That led to wide adoption, but it also means condition varies wildly, especially with DIY-assembled units. Poor soldering, incorrect component placement, or missing calibration can turn a great module into a tuning nightmare. If you're buying a used Rev2, ask whether it was professionally built or tested. Look for signs of overheating, cold joints, or misaligned panels. Most issues are fixable with basic troubleshooting, and the circuit is well-documented.

One thing to watch for is early Rev2 units with the LFO mode bug. If the seller can't confirm it's a post-fix version, assume it needs the capacitor mod. The fix is simple, but it's an extra step for buyers who just want a plug-and-play module. For those reasons, the safest bet is a post-2020 Rev2 or a well-tested original. Neither will appreciate much in value.