Softube Saturation Knob Explained: Keep High vs Keep Low, Every Control, and a Settings Chart by Job

The short answer: Softube Saturation Knob is a free saturation plugin with one big knob and one switch. The knob sets the amount, from OFF (fully counterclockwise, no saturation) to heavy clipping. The Saturation Type switch decides where the distortion lands: Keep High saturates the low end and keeps the highs clean, Keep Low saturates the high end and keeps the lows intact, and Neutral distorts all frequencies equally. The names tell you what stays clean, not what gets distorted. For a fatter bass line, start on Keep High; to squash a drum loop and keep the kick, use Keep Low; for warmth on vocals and synths, Neutral, a little past OFF. It's free through Softube Central with a Softube account and an iLok account (no physical dongle needed), for hosts that load VST, VST3, AU or AAX on macOS and Windows. There's no Mix knob, so for parallel saturation, put it on a return track.

I use free saturators next to paid ones on my own releases (Sony, Universal, Ultra, Dim Mak), and Saturation Knob is the one-knob pick in the best free saturation plugins. It's free and there are no affiliate links on this page. I sell a mastering chain with a tube saturation stage, disclosed at the end.

What Saturation Knob is

Softube calls it "a modeled output distortion that can be used anywhere you need some grit," and suggests it to "fatten up bass lines, add some harmonics and shimmer to vocals, or simply destroy your drum loop." That range is the point: at low settings it's warmth and density, and turned up it's obvious distortion. It sits right on the line between saturation and distortion.

What you need to know before installing it:

• Free, through Softube Central. Softube's page says to create or log in to a Softube account and download Softube Central, its app for installers and licenses. You also need an iLok account, but Softube says no physical iLok is required. Internet access is needed for downloading and managing the license.
• Formats and systems. Softube's requirements list hosts that load AU, VST, VST3 or AAX, on macOS Sonoma 14, Sequoia 15 and Tahoe 26, and Windows 10 (64-bit) and 11. Softube's general system requirements say Apple silicon is supported natively. So it loads in Logic (AU), Pro Tools (AAX), and FL Studio, Ableton Live, Cubase and Studio One (VST3).
• Three versions in one. The download covers the native plugin plus versions for Softube Modular and Amp Room. It's also part of Softube's paid Flow Mixing Suite and Flow Complete Suite, so suite owners already have it.
• Not the same as Softube's paid saturators. Harmonics and Tape are separate, paid Softube plugins. This page is about the free one.

Every control, explained

Softube's manual for Saturation Knob is written for the Modular version, which has the same knob and switch. The control names below are from Softube's plugin screenshots and that manual.

What it doesn't have matters as much: Softube lists no Mix (dry/wet) control, and the plugin face has no tone control. One knob, one switch, by design. Softube's Extended Features manual also describes a bottom panel with Headroom, a High Pass filter and Phase Invert on plugins that support it; check which of those your copy shows before you count on them.

Keep High vs Neutral vs Keep Low

This is where most people get it backwards. Each mode is named for the part of the spectrum it keeps clean.

Some guides describe the three modes as different harmonic orders. Softube's own manual describes them as which part of the spectrum gets distorted, and that's what you hear, so go by the table above.

How to run it in parallel (there's no Mix knob)

Parallel saturation keeps the dry signal's punch and blends the grit underneath, and on anything with sub it's the safer move. With no Mix control, do it with routing:

1. Create a return (aux) track and put Saturation Knob on it, set harder than you would on an insert.
2. Send the source to it and bring the return up under the dry track.
3. On bass and 808s, high-pass the return after Saturation Knob, around 100 Hz, so the return adds only harmonics and the dry track carries the sub.
4. Level-match the blend by toggling the return on and off at the same perceived loudness.

FL Studio users can skip the return: every mixer effect slot has its own mix knob.

Saturation Knob settings chart, by job

Softube doesn't publish a scale for the knob, so positions are clock positions, with OFF at about 7 o'clock. They're starting points; set the final amount by ear, level-matched.

The 808 row matters most on beat-driven records: phones can't play the fundamental of most 808s, so the harmonics a saturator adds are what carry the note on small speakers. How to mix 808 and kick covers who owns the sub before you add any. On the master, Saturation Knob is a light touch at most; what a mastering chain is shows where saturation sits, right before the clipper and limiter.

How to set it up

1. Install it through Softube Central, from softube.com only. Free plugins from mirror sites are how adware gets installed; the CamelCrusher story is the cautionary tale.
2. Clean up first. Saturation brings up whatever is there, mud and resonances included. EQ before it.
3. Insert it on the track, or on a return for parallel (steps above).
4. Pick the Saturation Type from the chart for the job.
5. Turn the knob up from OFF until you hear it on the loudest part, then back off a notch. It usually sounds slightly too little solo and right in the mix.
6. Level-match. Open the Extended Features panels and click Gain Match Input, or match by ear. Saturation adds level, and louder always wins a mismatched test for a few seconds.
7. Compare with bypass, then check on a phone speaker and in mono.
8. Automate it if the hook needs more grit than the verse.

Mistakes that turn warmth into mud

• Reading the mode names backwards. Keep High distorts the lows. If the bass got fuzzy when you wanted the cymbals gritty, flip the switch.
• Saturating the 808's sub on the insert. The fundamental smears and fights the kick. Use the return with a high-pass, or Keep Low on the insert if you only want the upper part of the 808 touched.
• Saturating out-of-tune parts together. Softube's manual notes that the distortion gets harsher when the input has inharmonic frequency relationships, and more pleasing when they're harmonic, the same principle as a guitar power chord. An 808 that's off the song's key, saturated on a bus with the music, gets harsh fast. Tune it first.
• Saturation Knob on every channel. Eight saturated sources fight for the same midrange. One or two, on purpose.
• Judging it louder. Gain Match Input, every time.
• Using it to make the master loud. That's a clipper and limiter job, done in small amounts. The best clipper plugins covers that stage.

Saturation Knob vs other free saturators

Saturation Knob wins on speed: two decisions and you're done. What the others add is control, a dry/wet mix or tape behavior. When the grit should be the sound, not just density, the best distortion plugins ranks the free, stock and paid options from Trash Lite to Decapitator.

Where I land (and the disclosure)

Saturation Knob earns its place in every free plugin folder: one decision about where the distortion lands, one about how much, and it sounds good from a touch of warmth to a wrecked loop. Learn the switch, run it in parallel on anything with sub, and level-match before you judge.

Saturation on a master is a different dose: a stage you only notice when you bypass it. The Ultimate Master Chain for Plugin Alliance has that stage built in. Black Box Analog Design HG-2 is its tube saturation and harmonic density stage, and two of its 10 macros are about color: DENSITY (harmonic richness, body and perceived loudness, while preserving clarity and punch) and SAT (parallel tube saturation, the blend Saturation Knob can't do without a return track). It ends in bx_clipper into bx_limiter True Peak. The Ableton rack is built for Live 12, there's a separate Logic build, and you'll need the Plugin Alliance plugins, typically through a Core or Pro subscription. It doesn't use Saturation Knob. I'm biased; Saturation Knob barely past OFF before your stock limiter teaches the same move for free.

Quick answers

Is Softube Saturation Knob free? Yes. You get it free through Softube Central, with a Softube account and an iLok account (no physical iLok required). It's also included in Softube's Flow Mixing Suite and Flow Complete Suite.

What's the difference between Keep High and Keep Low? Keep High saturates the low end and keeps the highs clean, which fattens bass and kick weight. Keep Low saturates the high end and keeps the lows intact, which is how you squash a drum loop without losing the kick. Neutral distorts all frequencies equally.

Does Saturation Knob work in FL Studio, Logic and Pro Tools? Yes. Softube supports hosts that load VST, VST3, AU or AAX, so it runs as VST3 in FL Studio and Ableton Live, AU in Logic and AAX in Pro Tools, on macOS 14 and later and Windows 10 and 11. Softube says Apple silicon is supported natively.

Is Saturation Knob good on 808s? Yes, in parallel. Put it on a return on Keep High, high-pass the return around 100 Hz, and blend it under the dry 808. The harmonics make the 808 audible on phones while the dry track keeps the sub clean.