Undertow — Instruction Manual

476 Productions | 0.22 | Mac AU / VST3; Windows VST3 build pending

Overview

Undertow is a multiband bass tone processor. A compressed clean low band anchors the sound while separate mid/high drive paths add grind and attack. Pre and post parametric EQ, dynamic bands, gate, cabinet IR and harmonic enhancement shape the result. It does not model a specific amplifier.

Main order: Input / Pre EQ > Gate > three-band tone engine > Post EQ > Output control > cabinet IR > Bass Harmonics > preset reference trim > Output Safety > final meters. The Output knob is before IR and harmonic generation; the final meter measures all of them. The global Processed/Blend control blends the tone engine's dry/processed paths; it is not a bypass for every later processor.

Installation and Compatibility

Mac: AU for Logic and VST3 for compatible hosts. The universal bundles contain Apple Silicon and Intel code, targeting macOS 11 or newer. Native Apple Silicon and Intel-under-Rosetta checks have passed; physical Intel hardware and individual DAW combinations still require testing.

The Mac package installs to /Library/Audio/Plug-Ins/Components and /Library/Audio/Plug-Ins/VST3. It preserves matching older user-scoped copies in the logged-in user's Undertow/Plugin Backups folder so they do not shadow the new system copy. Close DAWs first, install, then restart/rescan.

Windows x64 VST3 targets a compatible 64-bit host. Windows packaging and validation are pending; the Mac installer does not install on Windows. AU is Mac-only. AAX, Windows ARM-native and 32-bit builds are not supplied.

Controls and Navigation

The seven lower section buttons always remain available. Their highlighted background identifies the section on screen. Dots report processing status: teal enabled, grey inactive, amber audition/solo/mute, learning, or an enabled IR with no file. Hover a section for the exact status. Input / A-B reports its slot in the tooltip; Band Balance reports solo/mute status.

Knob value fields support numerical entry. The window is resizable. Help opens the quick guide, instruction chapters, troubleshooting and About information. All in-plug-in documentation works offline.

Tone Engine and Crossovers

Input sets the drive level entering the processing chain. Low split is 60–350 Hz; High split is 500–4000 Hz. DRIVE BANDS shows shaded ranges and draggable crossover lines. The low-band handle changes Low weight/body; mid/high handles change their processed levels. Double-click a drive handle to reset it.

Low comp increases low-band compression; its separate LOW COMP meter shows gain reduction. Low weight changes the processed low band's level. Mid drive and High drive set distortion amounts. Attack adds or softens emphasis, High cut controls the engine's upper rolloff, and Blend sets the engine's processed amount. These controls remain available below the selected section.

Parametric EQ

PRE EQ and POST EQ each provide eight bands. Choose Bell, Low shelf, High shelf, High pass, Low pass or Notch. Frequency spans 20 Hz–20 kHz; gain spans -24 to +24 dB; Q spans 0.1–18 where applicable. Disabled controls do not apply to the selected shape.

Switch DRIVE BANDS off to edit EQ nodes. Drag a node to change frequency/gain, scroll for Q, double-click empty graph space to add a band, and double-click a node to bypass it. Numbered buttons select bands. EQ enabled bypasses only the selected EQ stage. RESET EQ resets that stage's eight bands.

Pass/shelf slopes include 6, 12, 18, 24, 36 and 48 dB/oct. Bell edge modes provide 12/24/36/48 dB choices; their Q retains the half-gain bandwidth. Notch does not use adjustable slope. Pass/shelf resonance depends on the selected slope and Q. This is Undertow's EQ implementation, not a claim of equivalence to another EQ product.

Dynamic EQ and External Sidechain

Downward dynamics are available on bell and shelf bands. Threshold is the band detector's dBFS threshold. Ratio ranges from 1:1 to 20:1 with a fixed 6 dB knee; Maximum cut limits the extra attenuation. Attack and Release control how quickly that cut develops and recovers. Static gain and dynamic cut are separate.

The detector uses band-limited RMS, including a 5 ms detector stage. Displayed DETECT and CUT show detector level and reduction. Start with a modest maximum cut and lower threshold until problem notes react; do not assume every moving band improves the mix.

Each band selects Internal, External stereo, External left or External right. All external bands share Undertow's host sidechain input. Left/right can carry separate mono triggers if your host routes them that way. There is no independent host sidechain bus per band. An unconnected external input is silent; it does not fall back to bass input.

Kick ducking: send the kick to Undertow's sidechain in your DAW, then select an external detector on a low bell/shelf band. Use a short attack, an appropriate release and a small maximum cut. External input is a control signal and is not mixed into the output.

Distortion

Classic is the original saturation path. Modern adds staged clipping and band voicing while the separate low band remains clean. Tightness filters low frequencies from the distortion feed. Grind emphasizes mid growl; Bite emphasizes upper-mid attack. Fizz cutoff rolls off the distortion's top end, and Drive level balances its sum.

Tightness, Grind, Bite, Fizz cutoff and Drive level are Modern controls; they are disabled in Classic. Use Mid/High drive and the processed band levels to set intensity and balance. MID/HIGH activity bars represent level feeding the saturation stages, not a final output limiter.

Gate

Enable Gate and choose Expand 2:1, Expand 4:1 or Gate. Threshold selects the input level where attenuation begins. Range caps attenuation; Attack, Hold and Release shape opening and closing.

Set the threshold while playing your quietest wanted notes. If sustained notes disappear, lower the threshold, reduce Range or lengthen Hold/Release. A gate attenuates noise between notes; it does not remove noise under a sounding note. The reduction indicator shows its activity.

Cabinet IR

Load IR chooses a mono or stereo impulse response supported by the audio reader. Maximum length is 2 seconds, sample rate 8–384 kHz, and file size 16 MB. Invalid or unreadable files are rejected. Enable the IR to hear it; Level compensates its gain. Clear removes the loaded IR.

IR data is embedded in DAW state and full-tone .undertow files, allowing portable recall without the original source path. EQ-only presets do not include IRs. Only redistribute third-party IRs when you have permission; this product does not bundle your private IR library in its installer.

Band Balance

Set Low level, Mid level, High level and independent mid/high processed blends. Solo and Mute audition individual frequency paths. Multiple solos can be selected. Amber navigation status warns of solo/mute activity. Restore all solos/mutes before judging the full mix or printing a final track.

Input Calibration and A/B

Learn listens to a representative bass passage for three seconds and suggests an Input trim using a -18 dBFS RMS guide. Apply trim changes Input. It is a gain-staging aid, not a loudness standard or a substitute for your instrument's dynamics.

The tone A/B slots store complete working tones in the DAW project. Select A or B, Copy to the other slot, or Relearn measurements. Match B to A uses the captured RMS measurements; play the same passage for at least two seconds in each slot after controls settle. This is separate from factory preset reference matching.

Pre and Post EQ also have independent EQ-only A/B and Copy controls above the graph. They leave other processors intact. EQ comparisons are temporary working banks; full-tone A/B belongs to the DAW session. A saved user tone file contains the currently active tone, not both full-tone slots.

Bass Harmonics

Bass Harmonics adds generated upper harmonics from a low-band extraction after cabinet IR. Frequency (40–200 Hz) selects its tonal focus, Amount sets the added signal and Character blends second- toward third-harmonic emphasis. It is not a pitch tracker or sub-octave generator.

Start around 80 Hz with Amount 10–25%, then adjust in the full mix. Listen harmonics auditions only the generated signal while Enabled. Turn Listen off afterward. Harmonics can increase final peaks; use the final meter and Output Safety as needed.

Output Safety and Metering

Output Safety is optional stereo-linked sample-peak protection after all tone processing and reference matching. Ceiling ranges from -12 to 0 dBFS, default -1. It catches peaks without lookahead and recovers over approximately 80 ms. The meter shows reduction, with its bar scaled to 24 dB.

This adds no latency but is not true-peak limiting. Sustained heavy reduction can alter attacks and bass character. Lower Output or harmonic amount if the guard works constantly. Leave headroom for downstream processing and encoding; a plug-in later in your chain can still clip.

IN and OUT show current sample peaks. PEAK holds the highest final sample peak until reset. CLIP latches at 0 dBFS or above. Click the held peak display to reset it. With Safety off, output is not limited. Safety and factory matching default off when an older session omits their settings.

Presets and Level Matching

The top menu lists 19 factory tones and the user library. Genre factory presets load their complete EQ unless Keep EQ is on. The original seven engine presets preserve EQ. Factory programs reset the harmonic enhancer; user tone files restore their complete saved settings.

Match factory preset levels applies stored reference trims measured with one four-note phrase. It attenuates louder factory references toward the quietest and does not add makeup gain. It is approximate RMS matching, not LUFS normalization or automatic gain control. Different basses, edited controls, retained EQ and IRs can change perceived loudness. Existing personal presets without a reference trim use zero.

Save/Load work with full-tone .undertow files, including embedded IR. An asterisk marks changes since the saved tone. Delete moves only a selected library file to Trash and keeps the currently sounding tone.

EQ presets opens Save selected EQ, Load EQ file and the user EQ library. These .undertoweq files store just the selected EQ, including dynamics and detector choices. They do not replace the full tone. EQ tools offer starting points for common recording/mix issues. Replace clears the selected EQ before applying a tool; otherwise it adds into unused bands. Undo restores that EQ's previous tool/load result.

Mac user tones: ~/Library/Application Support/476 Productions/Undertow/Presets

Windows user tones: %APPDATA%/476 Productions/Undertow/Presets

User EQ files are in the neighboring EQ Presets folder. New full-tone format is 4; this version reads formats 1–4. Earlier builds may reject new files they cannot reproduce.

Live Use and Latency

The current oversampling route reports six samples of plug-in latency in offline checks. The clean-route impulse peak was eight samples in earlier verified checks. Hardware, buffer size, DAW scheduling, other plug-ins and IR onset add their own delay. Output Safety adds no extra lookahead delay.

Test your actual complete rig before live use. Offline AU/VST3 and Rosetta checks are not a certification of a live SuperRack rig. Load IRs and presets before performance where practical, and verify sidechain routing after changing hosts or sessions.

Licensing and Support

Purchase Undertow at https://undertow.476pro.com. Your license key and download link appear after checkout and are also emailed to you. One key activates up to two computers. A Count In Creator key does not activate Undertow.

In the plugin, choose Help > License & activation, paste your Undertow key, and click Activate. First activation requires internet access. After a successful check, you can work offline for up to 14 days. Use Check license to refresh that period. Use Deactivate this computer before moving a license to another machine. Activation stays in Keychain on Mac or Credential Manager on Windows, outside DAW projects and presets. Keep your computer’s clock accurate.

The commercial build requires activation before processing audio. A license change does not interrupt an already authorized audio stream; the next audio engine restart checks the current authorization. Open the license panel to check status before a live session.

The owner development build does not require commercial activation and identifies itself in the license panel. Customer installers contain the commercial build. The Help menu can copy version/platform diagnostics without including your audio, presets, license keys or project name. Retain your purchase receipt. For support or help moving from an unavailable computer, contact https://www.476pro.com/contact; keep your license key private.

The current Mac installer is independently distributed and is not Apple notarized. You may need to approve it in macOS Privacy & Security. Windows builds are still pending validation.