GROT User Manual

GROT is not clean on insert. Out of the box the MODE switch sits on GROTBOX, WET is at 0.0 dB and DRY is at -inf, so you are hearing the small-speaker voicing and nothing else: the signal is band-limited to roughly 320 Hz–3.2 kHz and pushed forward in the mids.

The three degradation knobs (DAMAGE, GROT and FILTH) all start at zero. The speaker is cheap, but it isn't broken yet.

Turn DAMAGE up to about 45.

The mids start to crumble first, then the top begins to rasp, and the whole thing develops a slow uncertainty: the drive level wanders at around 3 Hz, so the speaker never sounds settled. Somewhere past 40 you'll start hearing a mechanical flam a few milliseconds behind each hard transient: that's the loose driver slapping.

Sweep DAMAGE slowly from 0 to 100 once, and listen for the three stages: crunch, then the slap and the tearing buzz, then the whole driver failing in the last third.

Turn the GROT knob, the big one, up to about 30.

This is the sound of a speaker being driven harder than it was built for. The low mids compress, a bark resonance rises in the middle of the band, and the whole thing gets denser and angrier without simply getting louder.

Above 50 a second layer arrives: a bright, fizzy chainsaw saturation that adds serious bite. Try it, then come back down.

Turn FILTH to about 20.

Now the speaker is dirty as well as broken: a low-mid noise floor that opens whenever signal is flowing, occasional crackle from corroded contacts, and a grainy digital corruption underneath. FILTH is the only control that adds something that wasn't in your signal.

DRY and WET are two independent output levels rather than one blend knob. Right now DRY is muted and WET is at unity, so you're hearing the wreckage on its own, a full insert.

To use GROT in parallel instead, bring DRY up to about -6.0 and pull WET down to taste. The two paths are sample-aligned, so there's no phase weirdness in the sum.

Click to zoom

The VU meter at the top isn't an output meter. It reads damage done: how much of what's coming out was not in what went in. At 100% the change is as large as the original signal. In the red, GROT is putting out more junk than signal.

Use it to compare settings honestly, especially when the auto-gain has made two very different settings sound similar in level.

• One chapter per control, starting with Chapter 5 — MODE — choosing the speaker.
• Worked settings for real material: Chapter 11 — GROT in the mix.
• The controls hidden behind the meter: Chapter 10 — The hidden panel.

You mix, produce or sound-design, and you want to know exactly what each control is doing so you can reach for the right one instead of turning knobs until something happens. No DSP background is assumed. Where a number helps (a crossover point, a resonance, a threshold) it's given, because on a distortion box those numbers change what you reach for next.

• Getting started: what GROT is, how to install it, and the shortest route to a usable sound.
• The controls: one chapter per control on the front panel, in the order they appear: MODE, DAMAGE, GROT, FILTH, DRY and WET.
• Advanced: the hidden panel behind the meter (input staging and sidechaining), and a set of worked settings for real material.
• Help & reference: troubleshooting, a glossary, the full parameter table, specifications and support.

If you only read one chapter, read the quick start. If you only read two, read the quick start and MODE.

• DAMAGE, GROT, WET and so on are controls on the panel, spelled exactly as the panel spells them.
• Knob positions are given as percentages, matching the number the panel shows. "DAMAGE at 45" means the readout under the DAMAGE knob reads 45.
• DRY and WET are level controls and read in decibels, where -inf means fully muted and 0.0 means unity.

GROT is a distortion. It generates harmonics and noise that were not in your source, and at high settings it can be substantially louder than the signal you fed it.

The processing is entirely internal. GROT does not write to disk, does not phone home, and cannot damage your speakers other than by the ordinary route of being played too loud.

Most distortion plugins are circuits: a tube, a transistor, a clipper. GROT is a mechanical system. Everything it does is something physically going wrong at the point where electricity becomes air:

• the cone loses control and develops its own resonances;
• a loose driver slaps a few milliseconds after a hard transient;
• a slashed cone buzzes against its own cut edges, and jams;
• a voice coil hits its excursion limit and knocks on the back plate;
• grime and corrosion add hiss and crackle whether you asked for it or not.

That distinction matters in use. A circuit distortion sounds the same whatever you play through it. A mechanical one is program-locked: it responds to how hard and how low you hit it, it stays quiet when you stay quiet, and it falls apart in a way that follows the performance instead of sitting over the top of it.

Four controls do the work, and two set the blend.

Behind the VU meter there's a hidden panel with input gain, a spectral tilt, and a sidechain that lets another track drive the destruction. Chapter 10 covers it.

• Not a cabinet simulator. GROT will not make a DI'd guitar sound like a well-recorded amp. It will make it sound like it's coming out of something that should have been thrown away.
• Not an impulse response loader. There are no IRs and nothing to load.
• Not subtle by default, though it can be. With DRY and WET as separate levels, GROT is as usable as a parallel colour stage as it is as a wreck-everything insert.

Drum busses that are too clean and too polite. Synths that need to sound like they came out of something with a handle on it. Vocals that need to fall apart on one line. Bass that needs to be audible on a phone. Whole mixes, in parallel, when the arrangement is fine and the sound is boring.

Chapter 11 has worked starting points for each of those.

• macOS 11.0 or later
• An Apple Silicon (arm64) Mac
• A DAW that hosts AU, VST3 or AAX plug-ins

Your purchase or access code entitles you to a download link. Enter the code at tantrumaudio.co.uk/downloads/grot and the link is emailed to you. Keep that email, because the same link serves updates.

The file is GROT-0.1.1.dmg.

1. 1Open GROT-0.1.1.dmg. The window shows the plug-in bundles alongside shortcut folders pointing at the standard install locations.
2. 2Drag GROT.component onto AU Plug-Ins, for Logic Pro, GarageBand, and anything else that hosts Audio Units.
3. 3Drag GROT.vst3 onto VST3 Plug-Ins, for Ableton Live, Cubase, Reaper, Studio One, Bitwig and most other hosts.
4. 4Drag GROT.aaxplugin onto AAX Plug-Ins, for Pro Tools.
5. 5Enter your admin password when macOS asks. These are system-wide folders, so it will.
6. 6Eject the disk image.

You only need the format your DAW actually uses. Installing all three is harmless if you're not sure, and is what most people should do.

Note the leading /Library: that's the system-wide library at the root of your disk, not the ~/Library inside your home folder.

Logic Pro / GarageBand. Logic validates new Audio Units at launch. If GROT doesn't appear under Audio Units → Tantrum Audio, open Logic Pro → Settings → Plug-in Manager, find GROT and click Reset & Rescan Selection.

Ableton Live. Settings → Plug-Ins, make sure Use VST3 Plug-In System Folders is on, then click Rescan.

Pro Tools. AAX plug-ins are picked up at launch. Restart Pro Tools after installing.

Everything else. Rescan your plug-in folders from your host's preferences. Most hosts only scan at startup, so a restart usually does it.

Install the new version exactly the same way and let it replace the old files. Sessions keep their settings, because parameters are stored by name and every version of GROT reads earlier sessions.

Delete the files listed in the table above. GROT installs nothing else: no preference files, no support folders, no background processes.

Click to zoom

The order on the panel is not the order of the signal chain. The GROT knob is at the top because it's the one you reach for most. The actual chain runs input → MODE → DAMAGE → FILTH → GROT → limiter → DRY/WET sum, and is set out in full in Appendix B — Specifications.

Click to zoom

This is a real VU, with the 300 ms averaging ballistic that implies. It will not show you peaks and it isn't trying to. What it reads is unusual: not output level, but the size of the difference between output and input, relative to the input.

• Below 100%: the processing is a colouration. Most of what you're hearing is still your signal.
• At 100%: the change GROT has made is as big as the signal it was given.
• In the red: GROT is generating more than it was handed.

Because DRY and WET don't affect it, the meter tells you how hard the processing is working regardless of how much of it you've mixed in.

Every knob shows its value underneath. The three degradation knobs read 0–100. DRY and WET read in decibels, where -inf is silence and 0.0 is unity.

• Drag a knob vertically or horizontally to change it, or use the scroll wheel over it.
• Double-click the readout to type an exact value, then press Return.
• Hold ⌘, ⌥ or ⌃ while dragging to switch to velocity-sensitive mode, where a slow drag makes much finer changes than a fast one.

The panel is resizable and keeps its proportions. There are two ways to do it:

• Click the small percentage chip below the meter's right-hand corner and pick Small (70%), Medium (85%) or Large (100%). Right-clicking anywhere on the background opens the same menu.
• Drag the bottom-right corner of the window.

Your chosen size is stored with the plug-in, so it comes back the same way in that session and in new instances.

The first time you open GROT it sizes itself to your display, as large as fits the screen height, capped at 100%.

Every control is automatable, and every continuous control is smoothed so automation doesn't produce zipper noise or clicks: 80 ms on DAMAGE, GROT and FILTH, 30 ms on DRY, WET, GAIN and TILT. Filter coefficients are recalculated every 32 samples internally rather than once per host block, which is why fast knob moves stay clean.

MODE and the sidechain switch are discrete: they change instantly, with no crossfade. Automate them in a gap if you don't want to hear the join.

Click to zoom

Three positions, selected with the lever: DIRECT at the top, GROTBOX in the middle, BOOMBOX at the bottom. GROTBOX is the default.

No cabinet at all. The signal keeps its full bandwidth and no enclosure resonances are imposed.

Everything else still works: DAMAGE still tears the cone, the GROT knob still produces strain, FILTH still adds its noise floor. What you lose is the band-limiting and the box's own resonant character, and the gentle top-end sheen that GROT restores to the two speaker voicings, which DIRECT doesn't need.

Use DIRECT when the source already has a cabinet sound of its own, when you're degrading a full mix and can't afford to lose the extremes, or when you want the mechanics without the small-speaker tone.

A tiny, cheap, mid-forward box, the sort bolted to a PA column or rattling around in a practice combo.

The three resonances aren't fixed. As DAMAGE rises they get both louder and narrower, because a cone losing control doesn't just ring, it rings for longer. That's most of what makes GROTBOX the nastiest of the three modes.

GROTBOX also reacts hardest to the GROT knob. It's modelled as the smallest enclosure, and small enclosures get angry soonest, so the same GROT setting bites more here than anywhere else.

Use it on drums, on anything that needs to sound like it's coming out of a phone or a laptop, and whenever you want the transient slap to be obvious.

A big ported enclosure with far too much low end and a dull top.

The port is the whole point. It sits right where kick drums and bass live, it rings hard, and as DAMAGE increases it rings harder and longer until the woofer feels like it's on the edge of excursion.

BOOMBOX also drives the cone breakup harder than the other modes: DAMAGE is scaled up by 40% here, on the reasoning that a big cone gets flogged more for the same input. Expect the same DAMAGE setting to sound noticeably more broken in BOOMBOX than in GROTBOX.

Use it on bass, on kicks that need to feel oversized, and on anything you want to sound like it's being played through the back of a van.

Click to zoom

The signal is split into three bands (below 250 Hz, 250 Hz to 2 kHz, and above 2 kHz) and each is driven through its own asymmetric speaker-like shaper. The split is subtractive, so with DAMAGE at zero the bands sum back to exactly the original signal and there are no crossover artefacts to hear.

On top of that, DAMAGE controls five separate things that arrive at different points on the knob.

From zero: instability and tearing

Two things start immediately.

A slow random wobble, around 3 Hz, modulates how hard each band is being driven, so the speaker never sounds settled. It's scaled hard at the bottom of the knob, near-silent at low settings, and only really stirs once you push in.

And the torn cone starts to work. This is a modelled flap of slashed paper whose cut edges swing freely one way and jam against each other the other way, driven by the cone's own excursion. Crucially it doesn't add a sound: it modulates your signal, so the buzz is your own note rectified and choked. Quiet passages stay clean, loud ones tear up, and silence stays silent.

From about 40: the driver slap

Past 40 a mechanical flam appears on hard transients: the loose driver physically slapping about 10 ms behind the hit, rung through deep cone resonances.

It only fires on genuine transient onsets, and there's a 60 ms lockout after each one so it never degenerates into a flutter. It stays a physical event rather than an effect.

The slap follows MODE: high and tight in GROTBOX (315 Hz / 630 Hz, and boosted so it cuts through that box's mids), deep and slow in BOOMBOX (63 Hz / 126 Hz).

From about 60: terminal failure

The last part of the knob is the driver dying. The voice coil starts slamming into a shrinking excursion limit and knocking on the back plate, and the cone begins flapping an octave down, the flabby, motorboat blat of a blown woofer, with the radiation cutting out intermittently as it goes.

Like the tearing, all of it is derived from your signal. Nothing free-runs. Push nothing through it and it makes no noise at all.

Throughout: losing the top and finding its own resonances

Across the whole range the high end progressively collapses, and the broken cone develops two resonances of its own, a low-mid honk around 340 Hz and an upper-mid rattle around 1.6 kHz, that get both louder and narrower as the damage worsens. These live in the cone, not the box, so DIRECT mode gets them too.

The travel is deliberately not linear in effect:

The shaper drive itself plateaus around the middle of the knob. Past that point more crunch would just be harsher fizz, so the escalation is handed over to the tearing and terminal stages instead. The result is that the top of the knob reads as mechanical failure rather than more distortion.

Two things push the effective damage beyond where you set the knob.

• MODE. BOOMBOX scales the breakup up by 40%. The same setting is meaningfully more broken there than in GROTBOX or DIRECT.
• The GROT knob. A speaker under strain also breaks down faster, so turning GROT up advances DAMAGE too, by up to about 18% of the knob's travel at full GROT. This affects the character stages as well as the drive, so pushing GROT can bring the slap and the terminal failure in earlier than the DAMAGE readout suggests.

Click to zoom

The 55 Hz – 2 kHz band is pulled out and put under increasing pressure. Three things happen to it together as the knob rises.

Compression. The threshold drops from −6 dB down to −30 dB and the ratio climbs to 8:1, so the low mids are squeezed harder and earlier the further you go. Up to 12 dB of makeup gain keeps the band from collapsing under it.

Saturation. The compressed band is driven through an asymmetric saturator, with the drive rising steeply across the knob's travel.

Bark. A resonance sweeps downward from 1.1 kHz toward 420 Hz and rises by up to 10 dB as you turn it up. This is the vocal, shouting quality the control is named for, and it's what makes GROT read as effort rather than as fuzz.

The low mids bite early by design, so you'll hear real strain well below the halfway mark.

Compressing and saturating a 55 Hz – 2 kHz band costs you top end. Left alone, the knob would behave like a slowly closing 1 kHz filter.

To stop that, an active high shelf at 1.3 kHz ramps in as you turn up, reaching about +13 dB at the 60% mark. Above 60% it eases back to around +4 dB, because by then the chainsaw layer is supplying its own brightness.

The practical consequence: GROT gets denser and angrier as you turn it up, but not darker.

Past the halfway point a second, parallel layer ramps in: a dense, smooth, presence-boosted saturation in the manner of an HM-2 pedal, with a +7 dB lift around 3.2 kHz and a lid at 10 kHz to keep it from turning harsh.

This is a genuine change of character, not just more of the same. Below 50 the knob is strain and bark. Above 50 it's strain and bark plus a bright, fizzy, mid-forward buzz on top. The top quarter of the range is extreme by design, and the drive keeps extending well past what the numbers on the knob suggest.

MODE matters here too. GROTBOX is modelled as the smallest enclosure and responds most aggressively to GROT, while BOOMBOX is mid-sized and DIRECT is neutral. The same knob position is half again as strained through GROTBOX as through DIRECT, with BOOMBOX between the two.

Click to zoom

Grime

A continuous low-mid noise, band-limited to 150 Hz – 3.5 kHz with a honk around 1 kHz, then saturated for grit and tamed back down. It's modelled on the noise floor of an unmaintained console or a PA that's been in service far too long: dirty rather than hissy.

Grime is keyed to signal presence. It opens as soon as audio is flowing and closes in silence, over roughly 80 ms, with a slight level-dependent wobble so it isn't static. It is deliberately not a peak gate: it doesn't duck on transients and it doesn't pump.

Crackle

Sparse impulses with a fast decay tail: loose connections, dried-out contacts, a jack that needs cleaning. The rate rises with the FILTH setting and the timing is genuinely random, so it never falls into a pattern.

Corruption

A gentle, continuous loss of resolution. Bit depth is reduced smoothly from around 12-bit down to roughly 6- or 7-bit equivalent at maximum, then blended back at 25% strength. The result is a grainy, slightly compressed texture rather than the obvious stepping of a bitcrusher.

FILTH's response is quadratic: the bottom half of the travel barely does anything, and almost all of the effect lives in the top half. That's deliberate: it makes low settings usable as a texture rather than a commitment.

Because the grime is keyed to presence rather than level, it will not track a performance dynamically. It's either on with the signal or off in silence.

Click to zoom

A single mix control forces the two paths to trade against each other: more wet always means less dry. Two faders let you do things a blend can't.

• Full insert. DRY at -inf, WET at 0.0. This is the default.
• Parallel. DRY at 0.0, WET wherever it sits best. The dry signal keeps its full level and you add wreckage underneath it, rather than replacing part of your track with it.
• Wet only, quieter. DRY at -inf, WET at -6.0, when GROT is feeding something else downstream.
• Off. Both at -inf. Silence, which is occasionally what an automation lane wants.

Both read in decibels from -inf to 0.0, where -inf means fully muted and 0.0 means unity gain. Neither can boost: this is a blend stage, not a gain stage. If you need more level out of GROT, use the GAIN control in the hidden panel (see Chapter 10) or trim after the plug-in.

The scale is skewed so the useful part of the range (the top 12 dB or so, where most blending decisions actually happen) occupies the middle of the knob's travel rather than being crushed against the top.

Defaults are DRY -inf and WET 0.0.

The dry path is tapped from the input before any processing and the wet path carries no net delay, so the two are sample-aligned and sum cleanly. The driver slap adds a delayed layer but does not shift the through-signal, so there's nothing to time-align and nothing to cancel.

You can safely use GROT in parallel without a delay-compensation problem, and the plug-in reports zero latency to your host.

Between the processing and the output faders there are two stages you don't have controls for.

The level match. A slow trim (about 250 ms) nudges the wet path's energy back toward the input's, so moving DAMAGE and GROT changes the sound rather than the volume. It's deliberately sluggish, a level match rather than a compressor, and it's bounded to a 0.25× to 2.5× range.

Above about 60% DAMAGE this deliberately lets go and stops tracking, because the terminal-failure stage sustains long after the note that caused it has decayed. Matching it to a decaying dry signal would re-impose the note envelope and make the most extreme setting sound cleaner than the middle of the knob. A fixed compensation curve takes over instead, so the top of the knob stays relentless without becoming silly loud.

The limiter. A soft-knee limiter bounds the wet path before the faders. It catches peaks. It is not a mastering limiter and it isn't intended to be.

Click to zoom

Nothing in here is required. The front panel is the plug-in. This is where you go when the front panel isn't behaving the way a particular source needs.

Range: −24 dB to +24 dB. Default 0.0.

GAIN is applied to the plug-in's input ahead of absolutely everything else, so it sets how hard the source drives the degradation rather than how loud the output is.

This matters because every stage in GROT is level-dependent. The cone tears according to excursion, the slap fires on transient level, the terminal failure only rages when you push signal into it. A quiet source barely moves any of it, while a hot one wrecks everything at settings that sounded moderate a moment ago.

• Turn it up to make a quiet track break up properly without pushing DAMAGE and GROT to positions you don't want tonally.
• Turn it down to starve a hot source and get a subtler, more controlled version of the same settings.

The dry path, the automatic level match and the VU meter all follow the gain, so you are staging the plug-in rather than unbalancing it.

Range: −6 dB to +6 dB. Default 0.0.

TILT leans the input spectrum before any distortion, using two complementary shelves either side of an 800 Hz pivot. Turn it up and the top rises while the bottom falls, and turn it down for the reverse.

Because it sits ahead of everything nonlinear, it isn't an EQ on the result. It changes what the breakup has to chew on:

• Positive tilt feeds the chain more top end, so the breakup comes out fizzier and more brittle.
• Negative tilt feeds it more bottom, so the breakup comes out woofier and fatter, with more work being done by the low bands.

At 0.0 the two shelves cancel exactly, so the centre position is a true bypass and costs you nothing.

The sidechain lets another track drive GROT's destruction. When it's engaged, the sidechain's level rides GROT, DAMAGE and FILTH together between zero and wherever you've set them on the front panel.

That's the important part: the sidechain doesn't apply a fixed amount of some separate effect. It travels your own settings, so the whole character breathes with the key signal rather than a gain being ducked.

The switch

THRESH

Range: −60 dB to 0 dB. Default −24.0.

The sidechain level at which the gate is fully travelled. Below it, the effect is somewhere between clean and your settings, and at or above it the travel is complete.

The gate follows a fast (~10 ms) RMS of the sidechain, quick enough to move on individual drum hits, and is slewed over 15 ms so the ride itself stays click-free.

Setting one up

1. 1Send or route a key signal to GROT's sidechain input. In Logic that's the Side Chain menu at the top right of the plug-in window, and in most other hosts it's a send to GROT's second input bus.
2. 2Set the front-panel knobs to how you want the fully engaged sound.
3. 3Set the switch to OPEN or DUCK.
4. 4Adjust THRESH until the movement matches the key track's level.

Two things worth trying: a kick keying OPEN on a bass track, so the bass falls apart only on the beat, and a vocal keying DUCK on a synth pad, so the pad is wrecked everywhere except under the vocal.

GROTBOX · 45 · 25 · 15 · −6.0 / 0.0

Place GROT after your bus compression. The dry signal underneath keeps the kick's weight and the cymbals' top, and the wet layer supplies the mid-forward battered-PA sound and, crucially, the driver slap on kicks and snares.

The slap is the reason to use GROTBOX here: at 45 it's just engaged, and tuned high enough to cut through the box's own midrange. If you can't hear it, raise DAMAGE a few points rather than the WET level.

DIRECT · 20 · 65 · 0 · 0.0 / −12.0

DIRECT so the mix keeps its extremes, the GROT knob doing the work. The bark and the low-mid compression add density and forward presence under the mix without the muddiness that most tape and tube emulations bring.

Keep WET low and bring it up until the mix feels closer, then back off a decibel. Watch the VU: if the damage reading is much past 50% you're probably past what a mix bus wants.

BOOMBOX · 30 · 55 · 0 · −3.0 / 0.0

BOOMBOX's 65 Hz port gives the low end weight, and the GROT knob generates the upper harmonics that let a small speaker imply a fundamental it can't reproduce. The dry path underneath keeps the real bottom for systems that can play it.

If the low end starts flapping in a way you don't want, pull TILT down a couple of decibels in the hidden panel, which gives the low bands less to work with.

DIRECT · 10 · 0 · 55 · −inf / 0.0

FILTH doing almost everything. This is the grime and noise floor of a neglected playback chain without imposing a cabinet on the source. Good on sampled instruments and soft synths that sound too new.

Push FILTH past 60 for something that reads as tape-adjacent, but keep DAMAGE low or the character stops being neglect and starts being breakage.

GROTBOX · 70 · 40 · 25 · 0.0 / −inf

Set it up with DRY at unity and WET muted, so the vocal is untouched. Then automate WET up to around −4.0 for the line you want destroyed, and back down.

Automating WET rather than the degradation knobs means the destruction arrives already at full character instead of sweeping through the knob's stages on the way in.

BOOMBOX · 85 · 80 · 50 · −inf / 0.0

Not subtle, and not meant to be. At 85 the driver is in terminal failure, and at 80 the chainsaw layer is well past halfway. BOOMBOX drives the breakup 40% harder than the other modes, so this is about as far as GROT goes.

Put a limiter after it.

GROTBOX · 60 · 60 · 30 · 0.0 / −6.0, sidechain OPEN, THRESH to taste

Key it from the kick. The bass or pad you've inserted it on stays clean between hits and tears apart on the beat, because the sidechain travels the DAMAGE, GROT and FILTH knobs together rather than ducking a level.

Swap to DUCK for the inverse: everything wrecked except where the key signal lands.

• Set MODE first. It changes how every other control behaves, so choosing it last means re-doing the others.
• Stage the input before pushing the knobs. If a source isn't breaking up, GAIN in the hidden panel is often the right control, not DAMAGE.
• Watch the meter, not your loudness impression. The internal level match makes very different settings sound similar in volume.
• Trim after, not with the faders. DRY and WET only cut. Use a gain plug-in after GROT to make up level.

GROT is cheap. Per channel it's a handful of biquads and some shapers running at a 32-sample control-rate grid, with no oversampling and no lookahead. Dozens of instances on a modern Mac present no difficulty, and there is no latency to compensate anywhere in a session.

GROT doesn't appear in my DAW.

Rescan your plug-in folders from your host's preferences, and restart the host, because most only scan at launch. Then confirm the file is in the right place: /Library/Audio/Plug-Ins/Components/GROT.component for AU, /Library/Audio/Plug-Ins/VST3/GROT.vst3 for VST3, /Library/Application Support/Avid/Audio/Plug-Ins/GROT.aaxplugin for AAX. Note the leading /Library: the system one, not ~/Library inside your home folder.

Logic says the plug-in failed validation.

Open Logic Pro → Settings → Plug-in Manager, find GROT, and click Reset & Rescan Selection. If it still fails, check there isn't a second, older copy of GROT.component installed elsewhere, because Logic will keep using a stale one.

An update doesn't seem to have installed.

Same cause, usually. Delete every copy of the plug-in you can find, then install the new one and rescan.

macOS says the developer can't be verified.

It shouldn't, because GROT is signed with a Tantrum Audio Developer ID, notarised, and the ticket is stapled to the disk image. If you see this, the download was incomplete or corrupted. Re-download rather than overriding the warning.

Everything went band-limited and mid-heavy the moment I inserted it.

That's GROTBOX, which is the default MODE, heard on its own because DRY starts at -inf. It's working correctly. Switch MODE to DIRECT for full bandwidth, or bring DRY up to blend the untouched signal back in.

I can't hear the slap on kicks.

The driver slap engages above 40 on DAMAGE and ramps in from there. Below that only the breakup and instability are running. Get DAMAGE above 40 and use GROTBOX, where the slap is tuned high and boosted so it cuts through. Also check the source actually has hard transients. The slap fires on onsets, and there's a 60 ms lockout after each one so it can't flutter.

DAMAGE sounds almost the same at 30 as at 60.

Check MODE first. Through DIRECT's full bandwidth the breakup is far less obvious than through GROTBOX's narrow, resonant band. Then check your input level, because every stage in DAMAGE is excursion-driven, so a quiet source barely moves it. Raise GAIN in the hidden panel rather than pushing DAMAGE further.

The top of the DAMAGE knob sounds cleaner than the middle.

It shouldn't, and this was specifically designed out: above 60% the level match stops tracking so the terminal-failure stage isn't ducked back down. If you're hearing it, check whether something after GROT is compressing hard.

GROT sounds like it's just closing a filter.

It shouldn't, because an active high shelf compensates for exactly that. Check you haven't got MODE on BOOMBOX, whose top end is dark by design (4.5 kHz), and check nothing downstream is reacting to the level change.

Noise between notes.

That's FILTH, and it's intentional: the grime opens with signal and fades in silence, but at high settings it's audible at low signal levels too. Automate FILTH down for the gaps, or gate after GROT.

The output is clipping.

The soft limiter sits on the wet path only, before the output faders. The DRY + WET sum isn't limited, so pushing both faders up with DAMAGE and GROT high can exceed 0 dBFS. Add a limiter or a gain trim after GROT.

The level ducks for about a second when a loud passage starts.

This is a known behaviour of the automatic level match at high DAMAGE and GROT settings. Distortion adds energy, so a sudden loud onset makes the wet path measure hotter than the dry one and the trim pulls down, but its 250 ms slew means you hear the correction after the onset rather than at it. Workarounds: lower DAMAGE or GROT slightly, or drop GAIN in the hidden panel and make the level up after the plug-in.

Two very different settings sound the same volume.

That's the level match doing its job. Use the VU meter's damage reading to compare how hard the processing is actually working.

The effect is moving on its own and I haven't connected a sidechain.

Set the sidechain switch to OFF. In Logic, an Audio Unit's sidechain bus is fed the channel's own signal when no source is selected, so with the switch on OPEN or DUCK the track ends up keying itself. OFF is the default for this reason.

The sidechain doesn't do anything.

Check three things: the switch isn't on OFF; a key signal is actually routed to GROT's second input bus; and THRESH is somewhere near the key signal's level. Also remember the gate travels your knob positions: if DAMAGE, GROT and FILTH are all at zero there's nothing for it to travel to.

Dragging the corner doesn't resize it.

Logic doesn't allow Audio Unit windows to be resized that way. Use the percentage chip under the meter's right-hand corner, or right-click the background, and pick Small, Medium or Large.

It opened at a strange size.

GROT remembers the last size you used. Pick one from the size menu to reset it.

Appendix C — Support has the contact details and the information worth including when you write in.

DRY and WET run from −60 dB to 0 dB. The bottom of the range is treated as -inf, fully muted, not −60 dB. Neither can boost above unity. The scale is skewed around −12 dB so the range you actually blend in occupies the middle of the knob's travel.

THRESH is skewed around −24 dB for the same reason.

DAMAGE, GROT and FILTH are stored as 0–1 internally and displayed as 0–100. Their audible response is not linear in that number. See the individual chapters for what happens where.

Filter coefficients and drive amounts are recalculated every 32 samples rather than once per host block, so a knob move steps in small increments regardless of your buffer size.

Some controls change what others do. These are deliberate.

GAIN and TILT are not affected by the sidechain. DAMAGE does not feed FILTH: cone breakup is signal-related, while grime and crackle belong to neglect alone.

Everything above is saved with your session, along with the window size. Settings are stored by parameter name, so sessions move safely between GROT versions and between AU, VST3 and AAX.

1. 1GAIN: input staging, ±24 dB, ahead of everything. The dry path is tapped here, so the DRY fader hears the staged input.
2. 2TILT: ±6 dB complementary shelves about 800 Hz.
3. 3MODE: cabinet bandwidth and resonances (skipped entirely on DIRECT).
4. 4DAMAGE: 3-band breakup, cone modes, driver slap, tearing, terminal failure, HF collapse.
5. 5FILTH: grime and crackle added, bit corruption applied.
6. 6GROT: low-mid compression, bark, saturation, chainsaw.
7. 7Sheen: top-end air, on the cabinet voicings only.
8. 8Level match: about 250 ms, bounded to 0.25×–2.5×.
9. 9Soft limiter: wet path only.
10. 10× WET, summed with the tapped dry × DRY, to the output.

Nothing else is installed: no preference files, no support folders, no background processes.

Email tom@tantrumaudio.co.uk. GROT is a young plug-in and real-world reports genuinely change what gets fixed next, so please do write in, particularly if something sounds wrong rather than merely unexpected.

Chapter 12 — Troubleshooting covers the usual suspects: the plug-in not appearing after install, the immediate band-limiting on insert, the slap not firing below DAMAGE 40, noise in the gaps, and the sidechain moving on its own in Logic. Most reports turn out to be one of those.

• What happened, and what you expected instead.
• Your GROT version and macOS version.
• Your DAW and its version, and which format you're using (AU, VST3 or AAX).
• The settings: MODE, DAMAGE, GROT, FILTH, DRY, WET, and anything in the hidden panel. A screenshot of the panel is quicker than typing them out.
• Whether it happens on every source or one particular one, and at what sample rate and buffer size.
• For anything audible, a short audio example of the source going in. A few seconds is plenty.

Your download link at tantrumaudio.co.uk/downloads/grot serves the current version. If you've lost it, email the address above with the order details and it can be reissued.

Two things behave in ways that are worth knowing about before reporting them.

The level match can duck for about a second when a loud passage starts at high DAMAGE and GROT settings. Distortion adds energy, the wet path measures hotter than the dry, and the 250 ms trim corrects after the onset rather than at it. Lower the input GAIN and make it up afterwards if it gets in the way.

MODE and the sidechain switch click when changed during audio. They're discrete controls with no crossfade, by design. Automate them in a gap.

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