Effect 8 of 15 · Pedals

The EQ pedal: three bands

A low shelf, a mid peak you can move, a high shelf. With all three at zero it does nothing at all, and the measurement says so.

Play it alone All fifteen effects The whole board

Play it alone

Signal into the board

The test signals are synthesized by this page, sample by sample. Your instrument is asked for only when you press Start with “Your instrument” chosen, with the browser’s echo cancellation, noise suppression and automatic gain control switched off.

Output volume70%

Output levelsilent

Sample rate: not started
Processing latency: not started
Output latency: not started
Input latency: not started
Reported total: not started

Browser audio has latency: you hear each note a little after you play it. These are the browser’s own figures and they leave things out.

What the latency figures mean

The EQ, alone

In, this one pedal, out. Drag a knob sideways, or focus it and use the arrow keys or the wheel. The whole board has the rest.

EQ
Bass0.0 dB
Mid0.0 dB
Mid freq800 Hz
Treble0.0 dB

The signal

What it does to the signal

An equaliser turns particular ranges of frequency up or down. This one has three bands, in series.

Bass is a low shelf with its corner at 120 Hz: it raises or lowers everything below that by the amount set, and leaves what is well above it alone. Treble is a high shelf with its corner at 3.5 kHz, the same thing at the other end. Mid is a peaking filter: a hump, or a dip, centred on the frequency the Mid freq knob sets, with a Q of 0.9, which makes it about an octave and a half wide.

Each band reaches 12 dB up or down. The bands overlap: a large bass boost is still lifting the signal slightly at 800 Hz.

General definition: Wikipedia, “Audio equalization” (revision 1372652059, read 2026-09-28). Everything on this page about how this pedal works describes this page’s own code. It is built from standard Web Audio nodes.

To see your sound rather than shape it, the labs.llc EQ draws what your microphone hears, live, thirty-three ways. This pedal is a filter you hear; that one is a picture of the sound.

The graph

The graph, drawn.

audiocontrol: moves a setting, is never heard

Three filters in series, each a standard biquad.

The knobs

Every knob, in real units.

Knob	Range	Starts at	What it changes
Bass	−12.0 dB to +12.0 dB	0.0 dB	Gain of a low shelf whose corner is 120 Hz.
Mid	−12.0 dB to +12.0 dB	0.0 dB	Gain of a peaking filter, Q 0.9, at the frequency the next knob sets.
Mid freq	200 Hz to 3.2 kHz	800 Hz	Centre frequency of the mid band.
Treble	−12.0 dB to +12.0 dB	0.0 dB	Gain of a high shelf whose corner is 3.5 kHz.

Measured

What the test measured

Rendered offline, then measured

Switched off and rendered over 48,000 samples of the plucked-string signal, the output was identical to the input in every sample, and the pedal was not in the graph. [as described]
With all three bands at 0 dB the response from 20 Hz to 20 kHz was flat to within 0.0000 dB. [as described]
Bass +6 dB, Mid −9 dB at 800 Hz, Treble +4 dB: the measured gain was 5.96 dB at 30 Hz, −8.99 dB at 800 Hz and 3.99 dB at 16 kHz. (The bands overlap: the bass shelf is still lifting a little at 800 Hz, which is why the mid reads less than a 9 dB cut.) [as described]
Mid +8 dB with Mid freq at 2 kHz: the peak of the response was 8.00 dB at 2000 Hz. [as described]

Rendered in an OfflineAudioContext at 48,000 Hz in Chrome/154.0.8037.58, 2026-09-29 01:07 UTC. The test is work the page’s builder ran, not something your browser does when you open this page.

Limits

Three bands, and only the middle one moves.
Boosting can clip. Twelve decibels is four times the amplitude; a full-level signal boosted that far is beyond full scale, and the next pedal or the output will cut it off.

Where it goes in the chain

Either side of the drive, and the two are different tools. Before it, the EQ changes what the drive is given, and so which part of the signal distorts. After it, the EQ shapes the distorted sound. Wikibooks’ chapter on effects pedals describes both. This board’s default puts it after the drives. The whole order, and the reasons, are on the signal chain page.

← Fuzz Phaser →

Method

What is computed, and what is read.

Computed here, nothing fetched

Every sound on these pages is computed in your browser by the Web Audio API: 9 of the 15 pedals are graphs of the engine’s standard nodes, 5 are AudioWorklet processors, the wah is both, and the 3 test signals are synthesized sample by sample. No recording is loaded and no data feed is read. The one request the board’s own scripts make is for their AudioWorklet module, a file on labs.llc; the pitch detector is the one the Tuner uses.

Every effect was rendered offline with a known signal and measured: 73 of 73 checks came out as described. Nothing was tested on a real instrument or audio interface, only one browser was used, and nobody listened: the tests measure numbers, not tone. The method, the table of checks and what the latency figures mean are on the about page.

Sources

The W3C Web Audio API 1.1 and Media Capture and Streams specifications (W3C Document License); RFC 9110 and RFC 3986 for the share link’s fragment; GuitarPlayer’s guide to pedal order, quoted briefly; Wikibooks, “Guitar/Effects Pedals”; and each effect’s English Wikipedia article at a named revision (CC BY-SA). All read 2026-09-28; none is fetched by the page.

What happens to what you play

Audio from your input goes into the audio graph and out to your output device, and nowhere else: it is not recorded, stored or sent. Presets and the board as you left it stay in this browser’s local storage. A share link carries the board after the #, which browsers do not send to servers.