ADDAC 701.REV2 (2019–)

A no-nonsense analog oscillator that nails tuning, mixes waveforms on the fly, and doesn't quit when the temperature shifts

Overview

Plug in the ADDAC 701.REV2, turn the frequency knob, and within seconds you get a very clean sine wave. There's no warm-up dance and no coaxing it into compliance. It's just voltage-controlled oscillation that behaves. It's built around the CoolAudio version of the CEM3340 chip, and the 701.REV2 has the kind of pitch stability that makes you forget analog oscillators are supposed to drift. It tracks seven octaves, and it doesn't cost a month's rent.

This isn't ADDAC's first stab at a VCO. The original 701 had its fans, but enough tuning quirks that the company pulled it and went back to the bench. This revision was the result. The goal was simple: eliminate the detuning gremlins, improve the 1V/Oct tracking, and keep the character that made the first version worth revisiting. They rebuilt it with modern components and a smarter layout.

It’s not flashy, but it doesn’t need to be. The front panel is all business: a big frequency knob, an octave switch, a fine-tune dial, and a clean layout of outputs and controls. No hidden menus, no shift functions, no touch-sensitive nonsense. What you see is what you get, and what you get is a workhorse oscillator that can handle basslines, leads, FM experiments, or slow LFO duties without breaking stride. And while some oscillators make you choose between stability and soul, the 701.REV2 refuses to compromise—its waveforms have bite, presence, and a slight analog grit that never veers into wobble.

The waveform mixing section is where it stands out. Most oscillators give you discrete outputs and make you patch externally to blend. Here, three knobs - SIN/TRI, MIX, and SAW/RECT - let you build a composite waveform right on the panel. Want a triangle with a dash of sine, then some sawtooth for edge? Done. That kind of flexibility is usually reserved for much more complex modules, and ADDAC tucked it in without bloating the design.

Specifications

Manufacturer	ADDAC System
Production Years	2019–
Original Price	$189
Module Type	VCO / LFO
HP	8
Depth	35 mm
Current Draw +12V	60 mA
Current Draw -12V	60 mA
Current Draw 5V	0 mA
Oscillator Core	CEM3340 (CoolAudio)
Frequency Range	6 octaves (via knob), 7 octaves (1V/Oct tracking)
Fine Tune Range	±12 semitones
Waveforms	Sine, Triangle, Sawtooth, Pulse
Waveform Outputs	Sine, Triangle, Sawtooth, Pulse, Mix
FM Input	Linear FM with attenuator
Sync Input	Soft/Off/Hard Sync switch with input
Modulation Inputs	Pulse Width CV with attenuator, 1V/Oct CV, Linear FM CV
Mode Switch	LFO/VCO
Octave Switch	6-position (±3 octaves)
Weight	Approx. 180 g

Key Features

CEM3340 at the Core, But Not the Same Old Circuit

The CEM3340 was used in everything from the PPG Wave to the Prophet-5 Rev 3, and CoolAudio's modern reissue gives you that classic analog character without the vintage fragility. ADDAC also optimized the surrounding circuitry to maximize tracking accuracy and thermal stability. Early analog VCOs would drift with room temperature or after a few minutes of play, but the 701.REV2 holds its ground. Service technicians observe that the improved power regulation and thermal layout make it far less prone to the "warm-up wobble" that plagues cheaper designs. That matters when you're layering oscillators or using it in a live patch.

Waveform Mixing: A Hidden Superpower

Most oscillators treat waveform selection as a binary choice - you pick one and move on. The 701.REV2 treats it like a palette. The SIN/TRI knob blends sine and triangle, letting you dial in a smoother or more nasal low end. The SAW/RECT knob mixes sawtooth and pulse, adding harmonic complexity or tightening up the attack. The central MIX knob blends the two pairs, so you can create hybrid waveforms that don't exist in nature. Patch CV into the individual wave outputs or the mix controls, and you can animate the timbre in real time. It's a feature usually found in digital oscillators or complex wavetable modules, but here it's implemented with analog simplicity.

LFO Mode Done Right—Mostly

Flip the LFO/VCO switch, and the oscillator drops into low-frequency mode, useful for modulating filters, amps, or other oscillators. The frequency knob now covers a wide sweep from ultra-slow cycles to audio rate, and the fine-tune control lets you nail precise rates. There's a caveat. Early production units had a quirk where the octave switch didn't behave as expected in LFO mode, causing tuning mismatches when used with sequencers. Documentation shows that ADDAC addressed this with a capacitor change in later revisions. Collectors note that if you're buying used, ask whether the module has the updated component. Some owners have performed the mod themselves. Once corrected, the LFO mode gives smooth, jitter-free modulation that tracks just as reliably as the VCO side.

Historical Context

The ADDAC 701.REV2 arrived in 2019, right when the Eurorack market was hitting full maturity. Modules were getting more complex, more expensive, and in some cases, more gimmicky. In that climate, a straightforward, well-executed analog VCO stood out. ADDAC wasn't trying to reinvent the oscillator. It just had to track accurately, sound good, and stay in tune. The decision to use the CoolAudio CEM3340 was both practical and nostalgic. The original CEM3340 was discontinued decades ago, and while clones and substitutes exist, they vary wildly in quality. CoolAudio's version brought back the real circuit with modern reliability, and ADDAC was one of the first to use it in a production module.

Competitors at the time included the Intellijel Dixie II+ and the Make Noise Blippoo, both respected but with different priorities. The Dixie offered sub-oscillators and exponential FM, appealing to sound designers chasing complex textures. The Blippoo leaned into instability as a feature, embracing drift and chaos. The 701.REV2 didn't romanticize imperfection. It wasn't trying to sound "vintage" - it was trying to sound *right*. That made it a favorite among players who needed dependable bass and lead tones without the tuning anxiety. It also reflected a broader shift in the modular world: the rise of the "utility elite," modules that weren't flashy but were so well-built and reliable that they became backbone components in hundreds of systems.

Collectibility & Value

The ADDAC 701.REV2 isn't a rare bird, but it's not disposable either. It's common enough to find, but respected enough that it rarely gets sold off cheap. On the used market, prices range from $120 to $160 depending on condition and revision. Early units without the LFO capacitor mod tend to go for less, especially if the seller doesn't mention the fix. Near-mint modules with confirmed updates can still fetch close to the original $189 MSRP, particularly in Europe where shipping and import fees make new units pricier.

What breaks? Not much. The CEM3340 is sturdy, and the power regulation is solid, but like any analog module, potentiometers can wear over time, especially the fine-tune and pulse width knobs if used heavily. Service technicians observe that the jacks are standard 3.5mm types - durable, but not gold-plated - so oxidation can creep in after years of use. No catastrophic failure points have emerged, and there are no known batch defects beyond the early LFO quirk, which was addressed promptly. If you're buying used, test the 1V/Oct tracking across multiple octaves and verify the LFO mode syncs cleanly with a sequencer. Also, check that the waveform mix section doesn't crackle. Some users report minor noise in the mix pots if they haven't been cleaned, but it's usually fixable with contact cleaner.

Maintenance is minimal. A quick recalibration every few years is good practice, but unlike some analog oscillators, it doesn’t demand it. The module doesn’t require firmware updates or calibration trimmers buried under the panel—what you get is what you keep. That simplicity makes it a smart buy for beginners and veterans alike. It’s not the most feature-packed VCO on the market, but it’s one of the most trustworthy. And in a system where one unstable oscillator can ruin an entire patch, that’s worth its weight in gold.