The ValveStage

Tube microphone and instrument preamp · Gain · Drive · Pad — Six Walls

The ValveStage is a model of a PreSonus TubePre, the single-channel tube mic and instrument preamp, measured from a real unit (unofficial). The unit had a Russian 7025 (12AX7WA) in the tube socket. All of the distortion comes from one stage, the tube stage, and it depends only on how much level reaches it. The Gain dial comes after that stage, so it makes things louder without making them dirtier. Drive and the Pad come before it, and decide how hard the tube is hit.

Installing

Windows: run The-ValveStage-<version>-Windows-Setup.exe. Click Yes on the one security prompt and it installs the VST3 to C:\Program Files\Common Files\VST3\. If Pro Tools is installed, tick Also install the AAX version for Pro Tools to add the AAX to C:\Program Files\Common Files\Avid\Audio\Plug-Ins\.

macOS: open The-ValveStage-<version>-macOS.pkg. It installs the VST3 and the Audio Unit (for Logic and GarageBand) for all users; a Pro Tools (AAX) checkbox, off by default, adds the AAX. It is signed and notarized by Apple, so it opens with no Gatekeeper warning.

Then restart your DAW or rescan plugins. Prefer to place the bundles yourself? The portable download holds the plugin bundles and a READ ME saying where each one goes. The Installer can also keep The ValveStage up to date for you.

Controls

Control	Range	What it does
Gain	+8.9 … +49.1 dB	The unit’s Gain dial, after the tube stage. Clean and linear: it sets the level and nothing else. The knob follows the real dial’s taper, so a position on the knob means what it means on the hardware. The numbers printed on the dial (3 to 48) are not decibels; the real span is the +8.9 to +49.1 dB shown here.
Drive	0 … +19.3 dB	Extra gain in front of the tube stage. Turning it up pushes the tube harder, so it adds more of the tube’s sound, and it also makes the signal louder. Gain, which is after the stage, can bring the level back down.
Pad	on / off	Takes 19.2 dB off the signal before the tube. Use it for hot sources, or to keep a clean sound clean while Gain makes up the level.
80 Hz	on / off	The unit’s high-pass filter, a single pole at 79 Hz (a gentle 6 dB per octave).
Phase	normal / reversed	Reverses polarity.
Input	−40 … +12 dB	Ours, not the unit’s. A trim ahead of everything, and the control that matters most for the sound. A DAW track is at line level, far stronger than a microphone, so Input stands in for the distance between your track and a mic: lower it and the tube stays clean, raise it and the tube works harder. The clip light in its center comes on when the signal leaving the knob reaches 0 dBFS.
Output	−12 … +12 dB	Ours. A trim after everything, for matching levels. The clip light in its center follows the unit’s own clip light (see below).
Mix	0 … 100 %	Ours. Blends the dry signal with the processed one.

The sound depends on Input

The tube stage only knows how much level reaches it: Input, plus Drive, minus the Pad. Gain does not change it. That is why the same preset can be clean on a quiet track and dirty on a hot one. As a guide, with Input around −35 to −30 dB a normal track stays clean; by −20 to −10 dB you hear the tube; above that it is working hard. The factory presets set Input for you, so they behave like their names on a track near −18 dBFS RMS.

The plugin treats a sine wave at −18 dBFS RMS as −10 dBu, so 0 dBFS is +8 dBu.

The clip lights

There are two, one in the middle of each of the Input and Output knobs. Each holds for about a quarter of a second.

Light	Means
Input	The signal coming out of the Input knob has reached 0 dBFS (+8 dBu). A reminder to turn Input down; it is not a sound by itself.
Output	The preamp’s output has passed +20 dBu, where the hardware’s own clip light comes on. Past that the output stage clips hard, at a measured +21.3 dBu peak, whatever Gain and Drive are set to. A little of it is just loud; a lot of it is distortion.

The meter

The needle shows the output level. The meter on our unit would not move, so it could not be measured: this one is a generic VU meter with a spring-damped needle, not a copy of the hardware’s.

Presets

Each preset sets Gain, Drive, Pad, 80 Hz, Input, and Output together, as a complete sound for a track near −18 dBFS RMS. They are starting points, tuned by measurement: the Clean presets add almost nothing, the Warm presets add a little thickness, and the Hot presets are meant to be heard.

Preset	Gain	Drive	Pad	80 Hz	Input	Output
Clean Mic	34.0	0	off	off	−34	0
Close Condenser	45.2	0	on	off	−26	0
Voice-Over	34.3	0	off	on	−34	0
Warm Vocal	8.9	4.5	off	on	−6	−7.1
Warm Bass DI	8.9	7.4	off	off	−16	−0.2
Thick Drums	19.0	10.4	on	off	−10	0
Crunch Guitar	8.9	17.6	off	off	−10	−12
Blues Harp	8.9	19.3	off	on	−8	−12
Full Tube	8.9	19.3	off	off	−16	−12

Gain and Drive are in decibels, as the unit’s dials give them. Input and Output are the plugin’s own trims. Loading a preset sets all of them, including Input and Output, so it can change the level you were listening at.

Using the instrument input

The hardware’s 1/4″ instrument input is the XLR path with about 10 dB less gain ahead of the tube. The plugin has no separate switch for it. To get that sound, turn Input down by about 10 dB.

The toolbar

The bar along the bottom is the same on every Six Walls plugin: undo and redo, A/B comparison, the preset menu (factory presets plus Save as user preset…), the zoom steps, the version number, and the ? button, which opens this manual. User presets are small files in %APPDATA%\Six Walls\The ValveStage\Presets (~/Library/Application Support/Six Walls/The ValveStage/Presets on macOS).

Known limitations

Only the XLR path is modeled. The hardware’s 1/4″ output measured about 0.7 dB below the XLR at normal levels; the plugin does not add that. Phantom power is not modeled.
One tube. A Tung-Sol 5751 measured the same as the 7025 to within half a decibel, so there is no tube choice.
The meter is generic, as described above.
Accuracy. The dials and the tube stage match the unit within about a third of a decibel across the points we measured. On program material the plugin nulls against the unit at roughly −30 to −45 dB on snare and guitars, and about −34 dB on bass and drums; the deep low end is the part we modeled least precisely, and an acoustic guitar nulled less closely after the last low-end refit than before it.
The factory presets are tuned by measurement, one test recording each, and they are starting points. A very different source will land somewhere else; that is what the Input knob is for.
Latency. The model runs oversampled with a linear-phase filter. That adds a small, fixed delay, which The ValveStage reports to your DAW so it can compensate.

Credits & licenses

The version number is shown in the plugin’s bottom toolbar; the ? button there opens this manual.

JUCE 8 — built with JUCE (juce.com) under the free JUCE Personal license; the “Made with JUCE” splash on the editor is part of that license.
Fonts — Orbitron, Rajdhani, and IBM Plex Mono, under the SIL Open Font License 1.1.
Modeled on measurements of a tube preamp that Six Walls owns. Unofficial, not affiliated with or endorsed by its maker.