ADDAC205 Dual Oscilloscope & AWG (2011)

Two pocket-sized scopes and a waveform generator stuffed into 10 HP - useful lab gear or lazy repackaging?

Overview

The ADDAC205 Dual Oscilloscope & AWG doesn't hum or sweep when you power it up. It lights up two tiny white OLED screens and that's it. ADDAC System introduced it in July 2011 as a 10 HP Eurorack module. It doesn't make sound; it watches it. It shows voltages, triggers, CVs, and audio signals on its dual displays, so modular users get a window into what their patch is doing. It's a mixed signal oscilloscope with a built-in arbitrary waveform generator (AWG), spectrum analysis, and logic probing when paired with the ADDAC205B expansion. That's a lot of lab gear in a module smaller than a compressor pedal.

Owners report that the ADDAC205 doesn't feel like a ground-up Eurorack design. It appears to be two Gabotronics XMEGA Xprotolab oscilloscope boards - off-the-shelf, open-source handheld scopes - mounted side by side in a Eurorack shell. Each scope is built around that XMEGA board, with a menu-driven interface navigated by four buttons per side. There's no custom firmware overhaul and no deep integration with modular timing standards. It's two independent scopes and a waveform generator fitted into the format. Some users appreciate the compactness and real-time monitoring, especially for checking signal flow or diagnosing glitches. Others are less kind, noting that ADDAC seems to have bolted together two cheap boards and skipped writing a proper manual. You're expected to download the Xprotolab documentation to learn the controls.

It's a monitoring tool first. It's good for visualizing waveforms, confirming trigger timing, or sweeping frequencies with the built-in AWG. It won't replace a precision calibration rig, and one user put it this way: “Really good for checking what signals are doing but, a little tough for precision calibrations. Good monitoring tool.” Another owner said “looks bloody ace!” Another called it “very cool and handy.”

Specifications

Key Features

Two Scopes, One Rack Slot

The ADDAC205 packs two fully independent dual-channel oscilloscopes into a single module. Each side has two analog inputs with commutable switches, so you can toggle between signals or combine them in XY mode. The 128x64 monochrome OLED screens are high-contrast and sharp, but small - each display area measures just 21 × 10 mm. One user admitted, “It's a cool little scope. I just wish my eyes were 20 years younger.” For quick visual checks like seeing if a VCO is locking, confirming a gate's pulse width, or spotting clipping, it works well. The screen refresh rate is 128Hz, which feels smooth when zoomed in. Some users report sluggish redraws when zoomed out, which makes fast transient capture frustrating compared to alternatives like the O'tool.

More Than Just a Scope

The ADDAC205 also works as an arbitrary waveform generator with sine, triangle, and sawtooth outputs. It supports frequency sweeps and can generate waveforms at 8-bit resolution and up to 44.1kHz, with a maximum conversion rate of 1MSPS. The output voltage is ±2V, which is compatible with most Eurorack levels. It's not a performance synth voice, but it's handy for testing filters, calibrating oscillators, or injecting test signals into a patch. The AWG comes with a full set of scope tools: advanced triggering (normal, single, auto, with edge and level control), FFT spectrum analysis, horizontal and vertical cursors, and meter modes that display DC, average, and frequency readouts. You can also enable persistence and switch grid overlays.

Built on Open Hardware

Basing the module on the Gabotronics XMEGA Xprotolab cuts both ways. It inherits a capable, open-source firmware platform, but ADDAC didn't fully rework the interface for Eurorack use. The menu system works, but the button-press navigation can feel clunky mid-patch. As one user griped, there's no dedicated manual for the ADDAC version; you're pointed back to the Xprotolab docs. The digital expansion (ADDAC205B) adds eight digital inputs for logic analysis, with internal pull-up or pull-down resistors and a 2MSPS sampling rate, which turns the module into a mixed-signal oscilloscope. The manufacturer doesn't clearly document the expansion's gate input functionality, so users have to reverse-engineer its use.

Collectibility & Value

The ADDAC205 carries a listed price of $413, though early intentions pointed to a lower retail point - around 270€ when it launched in 2011. That makes it a premium product, especially given user perceptions that it's essentially two repackaged Xprotolab units. It's more expensive than the O'tool, another Eurorack scope, and the premium isn't clearly justified by performance. Some owners love its utility and compactness. Others question the value given the lack of custom firmware or enhanced documentation. There's no data on common failures or maintenance needs, but given the reliance on off-the-shelf boards, long-term repairability likely depends on the availability of Xprotolab replacement parts. As a niche tool rather than a sound-generating module, its collectibility hinges on utility, not nostalgia. It's not rare, but it's not common either.

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