ADDAC 805.VS2 (2019–2023)

A stereo voltage-controlled crossfader with split personalities—equal parts surgical mixer, chaotic morpher, and hidden CV blender that quietly reshapes how you route sound.

Overview

Plug four waveforms into the top row, twist a knob, and suddenly you're not just fading between sounds—you're orbiting them, like a satellite swinging past different gravitational fields. The ADDAC 805.VS2 doesn’t announce itself with flash or gimmicks; it’s the kind of module that creeps into your patches and never leaves, not because it’s flashy, but because it solves problems you didn’t know you had. At its core, it’s a stereo voltage-controlled signal router, but that description undersells the quiet brilliance of its architecture. It evolved from the company’s earlier 701 VCO waveform mixing section and the 701 X-Fade/Panner, but where those were more limited in scope, the 805.VS2 expands into full stereo territory with routing flexibility that borders on obsessive. You get two independent X-faders, each with manual control, CV input, and a reversible attenuverter—so you can invert the response of your control voltage without patching an inverter. That might sound minor, but when you’re trying to reverse a panning sweep or invert a morph sequence, it’s the difference between a clean patch and a rat’s nest of cables.

But the real magic is the master section: a stereo VCA that can also act as a third X-fader, letting you do four-quadrant mixing—meaning you can crossfade between any of four sources in a circular sweep, not just left-to-right or A-to-B. Want to morph from a sine wave to a square, then to noise, then to a sample, all while panning spatially? You can. The module handles both audio and CV signals, so you’re not just moving sound around in space—you can crossfade between modulation sources, blending an LFO into an envelope, or morphing between two sequencer outputs. It’s one of those rare modules that feels equally at home in a melodic patch or a noise experiment. And because it’s fully analog with high-quality VCAs, the signal path stays clean and quiet, even when you’re pushing multiple layers through it.

Still, it’s not without quirks. Early units, particularly those from the first production run, had an issue where the left and right X-fader channels didn’t match in gain response—one side would hit unity gain slightly earlier than the other, creating an off-center balance during manual sweeps. This wasn’t a design flaw per se, but a component tolerance issue that slipped through quality control. ADDAC acknowledged it and provided a DIY fix involving replacing two capacitors with more tightly matched ones—a tweak documented by users like Richard Brewster (aka pugix), who reverse-engineered the response curves and shared the solution publicly. Later units appear to have corrected this, but it’s something to test if you’re buying used. The module also uses nutless jacks, which some builders praise for clean panel aesthetics, but which can be a pain if a jack ever needs replacement—no standard nut means you’re dependent on ADDAC’s specific hardware.

Specifications

Manufacturer	ADDAC System
Production Years	2019–2023
Original Price	170€ (assembled), 129€ (DIY kit)
Format	Eurorack
Width	8HP
Depth	4.5 cm
Current Draw +12V	40mA
Current Draw -12V	40mA
Inputs	6 mono signal inputs, 3 CV inputs (with attenuverters), stereo direct input
Outputs	Stereo left/right outputs, mono sum output
VCAs	3 stereo voltage-controlled amplifiers (2 X-faders + 1 master)
Signal Path	Fully analog
Control Features	Dual X-faders with manual knobs, CV inputs, reversible attenuverters; master VCA/X-fader; routing switches for direct/stereo path
Functionality	VC crossfader, panner, 4-quadrant mixer, CV morpher, stereo VCA
Special Features	DC-coupled for CV processing, nutless jacks, DIY kit available
Weight	Approx. 200g (estimated)
Panel Color	Black (standard)
Availability	Discontinued (as of 2023)

Key Features

The 4-Quadrant Mixing Trick

Most stereo crossfaders let you move between two sources—A to B, left to right. The 805.VS2 lets you go further: by using the master VCA as a third crossfader, you can route four separate sources into the two X-faders and the direct stereo input, then sweep between all four in a circular pattern. This isn’t just a party trick—it changes how you think about transitions. Instead of a linear fade, you’re creating a morphing hub where textures rotate into each other, like a DJ with four turntables and a cosmic mixer. The manual doesn’t dwell on this, but the included signal flow diagram makes it clear: this is a module built for non-linear thinking. And because all controls have CV inputs with attenuverters, you can automate the entire rotation with a sequencer or random source, letting the module generate evolving textures on its own.

CV Morphing Beyond Audio

While many modules treat CV as secondary, the 805.VS2 treats control voltages as first-class citizens. Because it’s DC-coupled, you can patch envelopes, LFOs, or sequencer outputs into the inputs and crossfade between them just like audio. Imagine blending a slow triangle LFO into a stepped random CV, then panning that hybrid modulation to control filter cutoff and resonance in different proportions. Or crossfading between two envelope shapes to create a hybrid transient response. This kind of CV morphing is rare in Eurorack, and even rarer in a module this compact. It turns the 805.VS2 into a kind of “modulation blender,” letting you create hybrid control signals that would otherwise require multiple VCAs and mixers.

Routing Flexibility: Master Switches That Matter

The rear panel switches—often overlooked in module design—here become central to the workflow. You can route the left and right X-fader outputs through the master VCA or send them directly to the outputs. The stereo direct input can also be routed through the master or bypassed. These aren’t just on/off choices; they change the module’s behavior entirely. Use the master as a final level control? Or as a third crossfader? Or as a dry/wet mixer for external effects? The switches let you reconfigure the signal path on the fly, which is especially useful when you’re repatching quickly in a live set. And because the mono sum output is always active, combining both left and right channels, you can use the module as a six-channel mono mixer if needed—albeit with a unique, crossfader-based topology.

Historical Context

The 805.VS2 arrived in 2019, a time when Eurorack was deep into the “utility explosion”—a period where manufacturers began releasing increasingly sophisticated signal routers, mixers, and VCAs that weren’t sound generators, but enablers of complex patching. ADDAC, a Portuguese company known for blending analog warmth with digital precision, positioned the 805.VS2 as a spiritual successor to its own 701 X-Fade/Panner, but with stereo expansion and deeper CV control. At the time, modules like the Make Noise X-Pan offered high-end panning with logarithmic response, but with fixed routing and no attenuverters. The ADDAC, by contrast, prioritized flexibility over polish—giving users more control at the expense of some refinement. It wasn’t trying to be the most musical panner; it was trying to be the most adaptable. That made it a favorite among experimental patchers and those building systems focused on modulation morphing rather than traditional synthesis. Its closest competitors weren’t just other crossfaders, but modules like the Intellijel Quad VCA, the ALM Busy Circuits Pam’s New Workout, and the Mutable Instruments Blinds—all of which offered voltage control over amplitude, but none of which combined stereo routing, manual control, and 4-quadrant mixing in an 8HP package.

Collectibility & Value

The 805.VS2 was discontinued around 2023, not due to poor sales, but as part of ADDAC’s shift toward newer designs and limited-run modules. Today, used units trade between €180 and €250, depending on condition and whether they’re confirmed to be post-fix units. The main concern for buyers is the early gain mismatch issue—some units exhibit a noticeable imbalance between left and right channels during manual sweeps, especially around the 12 o’clock position. This can be fixed with a capacitor swap (Mouser part #RCE5C1H560J0K1H03B, as documented by users), but it’s not something every buyer wants to DIY. If you’re buying used, ask the seller to demonstrate both X-faders with a steady CV sweep and check for symmetry. Units with clean response curves command a small premium. The DIY kit version, priced at €129, was popular among builders and avoided the issue entirely if assembled with matched components. Today, complete DIY builds in good condition are slightly cheaper than assembled units, but the difference is minimal. The module’s black panel and nutless jacks give it a clean, modern look that ages well, and since it has no moving parts beyond pots and jacks, it’s generally reliable—assuming the original gain issue was addressed. For collectors, it’s not a “holy grail” module, but it’s a respected utility piece with a cult following among those who value routing depth over flash. If you’re building a compact, experimental system, it’s still a smart buy—just test it thoroughly.