Mainline Audio

The Fine Line

Precision Mastering Equalizer

A precise, restrained mastering EQ — exact numeric control, minimal visual noise.

Available Now · Introductory Price

$99

Regular price $149

Buy Now — $99 Download 14-Day Demo See what's inside ↓

The Fine Line mastering EQ plugin interface

Six-Band Precision

Six bands with proportional Q that widens as gain increases, so every move stays a broad, confident mastering gesture rather than a surgical mixing cut.

Three Phase Engines

Minimum, Natural, and Linear phase — genuinely different processing engines, not one algorithm with a mode switch bolted on. Choose the one the material calls for.

Learn more about phase in EQ →

Tilt & Contour

A global tilt macro for fast broad tonal moves, plus Contour's Transparent and Smooth voicing — reach for the whole curve without touching a single band.

Per-Band Channel Routing

Target each band independently to Stereo, Mid, Side, Left, or Right. Combine routing modes freely across all six bands for precise control of tone, center, width, and individual channels.

Channel Routing

Shape exactly where each band works.

Per-Band Targeting

Assign any band independently to Stereo, Mid, Side, Left, or Right. Different routing modes can be combined freely across all six bands, letting one band shape the center while another works on width or an individual channel.

Every Phase Engine

The same per-band routing remains available in Minimum, Natural, and Linear phase, so changing phase behavior never changes where your EQ is targeted.

Phase

Three engines. One curve.

Each phase engine processes the same six-band curve through a genuinely different signal path. Switch engines to match the mastering situation, not just the sound.

Minimum

The default engine. Zero added latency, classic minimum-phase EQ response.

Natural

A continuous, always-live engine that trades Minimum's zero-latency immediacy for linear-phase processing with lower latency than Linear.

Linear

Full linear-phase precision — greater frequency resolution with a fixed amount of added latency.

Monitoring

Four ways to work the curve

Every comparison tool is built to answer one question honestly: what is this specific move actually doing.

Bypass

Instant, click-free bypass — registered as the plugin's own host-visible bypass parameter for reliable A/B against your DAW's own compare tools.

Audition

Solo any band's contribution directly on the curve and in the signal — every other band recedes so you can hear and see exactly what one move is doing.

Isolate

Press and hold to preview a band in isolation — a fast way to confirm you're reaching for the right frequency before you commit.

A / B

Two full parameter snapshots, one click apart. Flip between them instantly while you decide.

Metering

See the curve, not just hear it

A light, honest read of what's happening — not a second metering suite bolted onto an EQ.

Spectrum Analyzer

Off, Pre, Post, or Pre + Post, with an opacity control that keeps the curve the hero, not the noise floor underneath it.

Output Level

A basic peak/level meter paired with Output Trim, plus Auto Gain's own compensation readout, so you always know exactly what's leaving the plugin.

Specifications

Technical Specifications

Parameter	Range
Band Frequency	20 Hz – 20 kHz
Band Gain	±18 dB
Band Q	0.1 – 10
HP / LP Slope	6 / 12 / 18 / 24 / 36 / 48 / 96 dB/oct
Tilt Frequency	20 Hz – 20 kHz
Tilt Gain	±6 dB
Output Trim	±24 dB
Phase	Minimum / Natural / Linear
Quality	Standard / High / Ultra
Contour	Transparent / Smooth
Band Routing	Stereo / Mid / Side / Left / Right — independently selectable per band
Formats	AU / VST3
Platform	macOS · Apple Silicon & Intel (Universal)

Mainline Audio

Available
Now.

VST3 & AU · macOS · Apple Silicon & Intel

FAQ

What is The Fine Line?

A precise, restrained mastering equalizer built for exact numeric control with minimal visual noise — six bands, three phase engines, Tilt, and Contour, with independent Stereo, Mid, Side, Left, or Right routing available on every band.

Can I get it now?

Yes — The Fine Line is available now.

What formats are supported?

VST3 and AU on macOS (Apple Silicon & Intel, Universal). AAX / Windows are not currently supported.

How many computers can I install it on?

Up to 2 computers that you own or control. Deactivate a machine at any time to free up an activation.

Is educational licensing available?

Educational and institutional licensing may be available for schools, labs, and training facilities. Contact Mainline Audio for details.

Do you offer a demo?

Yes. A fully functional 14-day demo — the same AU/VST3 installer as the paid version — is available with no audio interruptions, muting, or feature restrictions. Get it through the free demo checkout above; you'll receive download access by email. Once installed, choose Start 14-Day Demo when you open The Fine Line. No payment or license key required.

Will there be updates?

Mainline Audio may provide updates for The Fine Line at its discretion. There is no automatic in-app update check today.