Mix Tools

EQDRIFT

Three modules, three different answers to the same question — and filters that do not cramp.

£69 £89Launch price

See the measurements

Formats: VST3 · AU · Standalone
Operating system: macOS · Universal
Version: v1.0.0

What it does

Three equalisers. One curve you can trust.

Every digital EQ built on the bilinear transform has the same flaw. The transform squeezes the whole infinite analogue frequency axis into the space below Nyquist, so a filter's upper skirt gets compressed toward the top of the band. A 10 kHz bell at 44.1 kHz reads low where the analogue prototype would still be at full gain. The usual workaround — oversample the EQ — treats the symptom.

EQDRIFT designs its sections a second way. Poles are placed by mapping the analogue poles straight through the exponential, which warps nothing. The numerator is then solved rather than transformed, by requiring the digital magnitude to equal the analogue prototype's at DC, at the corner and at Nyquist. It costs a few extra transcendentals at design time and nothing per sample.

That is why Natural Phase, not Zero Latency, is the shipping default.

Key features

CLASSIC — 32 bands with dynamics on every one

Sixteen shapes, slopes from 6 dB/oct to brickwall, six phase modes, per-band mid/side placement, and a spectrum analyser that agrees with the curve drawn in front of it.

SPECTRUM — adaptive resonance suppression

Measures what the spectrum should look like around each frequency and pulls down whatever is protruding from it, only while it protrudes. Nothing is placed by hand. The eight-handle curve is not a gain curve — it is how hard the processor is allowed to work at each frequency.

TRACK — pitch-following EQ

Estimates the fundamental of what is played and hangs EQ nodes off its harmonics, so a cut on the third harmonic stays on the third harmonic as the notes change. FOLLOW is multiplied by the tracker's confidence, so as the detector loses the note, nodes slide back to their manual positions rather than freezing somewhere arbitrary.

Modulation is silent

Every section is converted to topology-preserving form before it processes a sample. A direct-form biquad has no physically meaningful state — when its coefficients jump, the state that suited the old transfer function is wrong for the new one, and it clicks. TPT state is its two integrator voltages, which stay meaningful whatever the coefficients do.

The picture is the filter

The curve on screen, the linear-phase kernel and the recursive filters are all derived from the same coefficients. The kernel is sampled from the filters that are already running rather than designed a second time, so linear phase and zero latency cannot disagree about magnitude.

Cascades that are actually Butterworth

Using 0.7071 for every section — which is common — gives a cascade 12 dB down at its nominal corner instead of 3, with a passband that droops for an octave above it. Every order from 2 to 16 is checked against the Butterworth magnitude to within 0.02 dB.

The interface

The EQDRIFT SPECTRUM module, with reduction hanging downward from the top of the plot as bites taken out of the ceiling. — EQDRIFT · 1 of 2

The EQDRIFT TRACK module, showing the detected fundamental as a bright vertical line with its harmonics dashed behind it. — EQDRIFT · 2 of 2

Audio

Audio demos for EQDRIFT are not published yet.

We would rather show you nothing than show you a demo that was not recorded through this plugin.

Measured

EQDriftTests and EQDriftBench · Apple Silicon · 48 kHz · 512-sample blocks

10 kHz Q=1 +12 dB at 44.1 kHz — bilinear error: 3.820 dB
10 kHz Q=1 +12 dB at 44.1 kHz — matched error: 0.678 dB (5.6× closer)
Measured response vs drawn curve: within 0.05 dB
Butterworth cascade accuracy, orders 2–16: within 0.02 dB
CPU — 8 static bands: 0.49 %
CPU — 32 static bands: 1.14 %
CPU — all three modules at once: 4.29 %
Mix return with every module inert: input to within 6e-08
Test assertions across both suites: 1006

Figures are produced by this plugin’s own test suite and benchmark, on the hardware and sample rate named above. They are not estimates.

Controls

Band editing

Double-click empty space: Create a band there. Double-click a node to remove it.
Drag / Shift-drag / Ctrl-drag: Frequency and gain / gain only / frequency only.
Wheel over a node: Q, multiplicative — shift for fine.
Alt-click: Delta-solo the band: hear only what it is doing.
Node bubble: Frequency, gain, Q, and on a dynamic band the gain it is being moved to right now. Power, shape, delta-solo and remove are one click away.

Dynamic bands

Mode: Chooses which side of the threshold engages the band and which way it then moves. The direction belongs to the mode, never to the sign of the gain.
Range: How far the dynamics may move the band from its resting gain. The whole travel is shaded in, with the live curve moving inside it.

SPECTRUM

FOCUS: How readily a peak counts as protruding.
SELECTIVITY: How narrow a feature has to be.
DEPTH: How far it can be pulled down.

TRACK

FOLLOW: How completely a node follows, interpolated in log frequency and multiplied by the tracker's confidence.
OFFSET: Cents around the node's harmonic. Dragging a tracked node sideways changes this — it keeps tracking.
LOWEST / HIGHEST: The instrument's actual range. The single most effective way to stop a detector wandering, and it costs CPU to leave them wide.
SOURCE: Audio, Sidechain or MIDI. On a synth already driven by MIDI, guessing the notes back out of the audio is strictly worse than reading them.

Technical details

Formats: VST3 · AU · Standalone
Operating system: macOS 10.13 or later
Architecture: Universal — Apple Silicon and Intel
Plugin code: Eqdr
Version: 1.0.0
CPU: 0.49 % for 8 static bands, up to 4.29 % with all three modules running

Worth knowing

Match EQ and resonance detection are implemented and tested in the DSP layer but are not yet reachable from the interface. They are not features of this release.