ADDAC System ADDAC805.VS2 (2020–)
A stereo voltage-controlled signal router that turns crossfading into a compositional tool. Deep and flexible, though not perfectly matched out of the box.
Overview
Plug in four very different signals - say a gritty square wave, a filtered noise burst, a slow LFO and a sample-and-hold staircase - and slide between them. That's the ADDAC805.VS2. It doesn't just mix or pan, it morphs. It comes out of the signal routing approach of the ADDAC701 VCO, and it's an 8HP Eurorack module that makes the crossfader a voltage-controllable gateway between sources. It's not flashy, but once you've used it to dissolve a sequencer line into a drifting CV landscape, you'll wonder how you patched without it.
The 805.VS2 is a stereo voltage-controlled signal router with two independent X-faders and a master stereo VCA that doubles as a third X-fader. That's what sets it apart. Each fader has manual control, CV input and a reversible attenuverter, so you can push signals forward or pull them back with precision. The module handles both audio and CV, so it can crossfade waveforms, blend modulation sources, or morph between control voltages driving other modules. It's the kind of utility piece that quietly becomes central.
It's built like a tank. The panel uses nutless jacks, which give it a clean, modern face and make installation easier. The analog signal path relies on high-quality VCAs, and the whole design is DC-coupled, so it shapes slow control voltages as comfortably as it routes audio. It has quirks, though. Some early units have mismatched response curves between the left and right faders, a subtle but noticeable imbalance that can throw off precise panning or crossfading. ADDAC has been responsive and offers a DIY fix involving a capacitor swap for affected units. It doesn't invalidate the module, but a careful buyer should test for it before committing.
Still, when it works as intended, the 805.VS2 sings. The exponential response of its VCAs gives a natural, logarithmic-like sweep that feels musical rather than mechanical. You don’t just switch between sources—you glide, smear, and dissolve. And because the master section can act as a stereo VCA or a third fader, you can layer control: use one fader to blend two drum loops, another to crossfade between two ambient pads, then use the master to fade the entire mix into silence or punch it up with a voltage-controlled swell. The direct stereo input adds another layer, letting you pipe in an external signal and route it through the master VCA for global dynamics control.
The normaling scheme means you can start simple - patch two signals and crossfade - and grow into the deeper tricks, like using the master as a 4-quadrant mixer to sweep between four independent sources. The mono sum output, which combines left and right, effectively turns it into a six-input mono mixer with a peculiar, layered character. It's not a clean summing amp. It's a color mixer, and it builds textures by stacking and fading.
Specifications
| Manufacturer | ADDAC System |
| Model | ADDAC805.VS2 |
| Production Years | 2020– |
| Original Price | 170€ (assembled), 129€ (DIY kit, excl. VAT) |
| Format | Eurorack |
| Width | 8HP |
| Depth | 4.5 cm |
| Power Consumption +12V | 40mA |
| Power Consumption -12V | 40mA |
| Function | VC Signal Router / Crossfader / Stereo VCA |
| Channels | Stereo (Left, Right, Master) |
| X-Faders | 2 dedicated + 1 via Master Stereo VCA |
| Inputs | 6 mono signal inputs (2 per X-fader channel), 1 stereo direct input |
| CV Inputs | 3 (one per fader channel: Left, Right, Master) |
| Attenuverters | 3 (one per CV input) |
| Outputs | Stereo Left/Right, Mono Sum |
| Signal Path | Fully analog, DC-coupled |
| VCAs | High-quality, low-noise voltage-controlled amplifiers |
| Available As | Assembled module or DIY kit |
Key Features
A Crossfader That Thinks in Quadrants
Most crossfaders move between two sources. The 805.VS2, thanks to its stereo architecture and master routing options, can handle four. Use the left and right X-faders to each blend a pair of signals, then use the master as a crossfader between those two pairs, and you have a 4-quadrant mixer. Patch four waveforms from a VCO, four LFOs, or four envelope generators, and sweep through them like a joystick moving across a 2D field. That suits evolving drones, granular-like textures, or shifting rhythmic layers. The manual doesn't dwell on this, but the signal flow diagram makes it clear.
Master Section: VCA or X-Fader?
The master channel is where the 805.VS2 shows its flexibility. It can work as a stereo VCA, applying global amplitude control to the left and right outputs, or as a third X-fader, blending the left and right channels. That means you can chain operations: crossfade two signals on the left, two on the right, then use the master to crossfade between those two results. Or route the stereo direct input through the master VCA to bring in an external synth or drum machine and control its level with CV. The routing is handled via internal jumpers or normaling behavior, so it's not instantly obvious, but once you map it, the possibilities multiply.
CV Routing with Attenuverters
Every CV input comes with its own attenuverter. The VCAs are sensitive - unity gain can be reached with as little as 1.5V in some cases - so being able to scale and invert control voltages is essential. To fade in a signal with an envelope but use only the rising edge, flip the attenuverter and dial it in. To modulate the crossfade position with an LFO but keep it subtle, attenuate the CV. You're not just automating a knob, you're setting how the automation behaves.
Historical Context
The ADDAC805.VS2 is a direct evolution of the signal routing concepts in the ADDAC701 VCO, where waveform mixing was already a standout feature. ADDAC System is a Portuguese boutique known for blending utility and expressiveness, and it has leaned into the idea that control voltage isn't just for pitch and filter. In the 2020s Eurorack landscape, where modules often prioritize novelty over depth, the 805.VS2 is a thoughtful refinement. It's not the first voltage-controlled crossfader - Make Noise's X-Pan and Intellijel's Pan Expander come to mind - but it's one of the few that offers three faders in a single module and allows 4-quadrant mixing.
It also fits a trend toward flexible, multi-role utility modules. Instead of buying separate VCAs, mixers and panners, users want modules that wear multiple hats. Compared to the X-Pan, the 805.VS2 is more flexible in routing and CV control but lacks the X-Pan's ability to pan crossfaded signals independently. It's less about stereo imaging, more about signal morphing. It doesn't have the bells and whistles of a digital crossfader, and its all-analog path gives it a warmth and immediacy that feels more tactile.
Collectibility & Value
As of 2026, the ADDAC805.VS2 remains in production and is not a vintage item by strict pre-2000 standards. It has earned a quiet reputation among Eurorack enthusiasts as a “must-have” utility. You won't see it on stage, but in deep modular setups it's often hidden in the back, doing heavy lifting. New units sell for around €170 from ADDAC directly, with DIY kits available for €129 (excluding VAT). On the secondhand market, assembled modules typically trade between $180 and $220, depending on region and condition.
The main concern for buyers is the potential for mismatched left/right response curves. This doesn't affect all units, but it's been documented in early production runs. The symptom is subtle: one fader reaches unity gain faster than the other, which can throw off stereo balance or precise crossfades. ADDAC has acknowledged the issue and provided a DIY fix involving replacing a capacitor (Mouser part # RCE5C1H560J0K1H03B) on the affected channel. Service technicians observe that the fix is straightforward for those comfortable with soldering, but it's a red flag for buyers who want a plug-and-play experience.
Other than that, the module is sturdy. There are no user-serviceable trimpots, so calibration isn't something you can tweak on the fly. The nutless jacks are durable, but some users report that the small panel text is hard to read without magnification - more an annoyance than a failure point. It's a relatively simple analog design with no microcontrollers or firmware, so long-term reliability is expected to be high, assuming standard Eurorack power and environmental conditions.
If you're buying used, test both faders with a steady CV and scope the output to check for response symmetry. Patch a constant voltage into both inputs and sweep the faders manually and via CV - listen for level imbalances or sudden jumps. Also verify that the attenuverters work smoothly in both directions. Given its role as a signal router, any instability here can ripple through an entire patch.
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