LED Graphic Equaliser
Real-time frequency display across 16 bands. Driven by your microphone or system audio. Built to replicate a 1990s hi-fi graphic equaliser.
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How to Use the LED Equaliser
Click Microphone or System Audio to start. Your browser will ask for permission to use the chosen source. Once granted, the LED columns begin responding immediately across all 16 frequency bands.
The Gain knob raises or lowers the input signal level, affecting how high the columns climb. The Sensitivity knob adjusts how the measured level maps to the display height — useful for calibrating the visual response without changing the actual signal. The large Volume knob controls the monitoring output level.
Each LED column has a red clip indicator at the top which lights when that frequency band hits maximum level. If it fires often, turn the Gain knob down. The clip indicator holds for around two seconds to catch fast transients. Tick the Peak Hold box to keep it lit until the level drops, rather than timing out.
- Microphone: picks up ambient sound or anything your mic captures in real time.
- System Audio: share a browser tab or application to see the frequency content of music or video. Works in Chrome and Edge on desktop. Tick the "Share audio" option when prompted.
- Frequency bands: the display runs from 60 Hz bass on the left to 16 kHz treble on the right, covering the full range of human hearing.
- Keyboard shortcuts: use + and - to adjust volume in steps, and Spacebar or M to toggle the mute.
Frequently Asked Questions
A graphic equaliser splits an audio signal into a fixed set of frequency bands and displays the energy in each band using a column of LEDs or a bar chart. The display updates in real time as audio plays, giving a visual picture of the frequency content of the sound. Low frequencies such as bass appear on the left, high frequencies such as treble on the right.
The red LED at the top of each frequency column is a peak clip indicator. It lights when the signal in that band reaches maximum level and holds for around two seconds. A clipping indicator tells you the input is too hot in that range and may be causing distortion. If it fires often, reduce the Gain control to bring the overall level down.
LED graphic equalisers were a common feature on mid-range and high-end hi-fi separates and integrated amplifiers throughout the late 1980s and 1990s. They gave listeners a real-time view of the music's frequency content, both practical for adjusting tone and visually impressive. The distinctive green glow of rows of tiny LED segments became one of the defining visual elements of consumer audio equipment from that era.
The display shows 16 frequency bands: 60 Hz, 100 Hz, 160 Hz, 250 Hz, 400 Hz, 630 Hz, 1 kHz, 1.6 kHz, 2.5 kHz, 4 kHz, 6.3 kHz, 8 kHz, 10 kHz, 12.5 kHz, 14 kHz and 16 kHz. These cover the full range of human hearing from deep bass through to the upper limits of audible treble.
The LED graphic equaliser breaks the audio signal into 16 frequency bands and shows the level in each one simultaneously, letting you see the tonal shape of the sound. The VU power meter shows the overall average level of the left and right channels as a single needle reading, in the style of a 1980s hi-fi amplifier. The two tools are complementary.
Click the Microphone button. Your browser will ask for permission — click Allow. The LED columns will immediately respond to sound. Use the Gain knob to raise or lower sensitivity if the display looks too quiet or if the red peak indicators fire constantly.
Yes. Click System Audio. Your browser will ask you to share a tab or screen — select the source and tick the Share audio option. The equaliser will display the frequency content of whatever is playing. System audio capture works in Chrome and Edge on desktop.
Sensitivity adjusts how the measured level maps to the LED column height. Turn it up to make the display more reactive to quieter sounds, or down if the columns constantly hit the top. Unlike Gain, which changes the actual signal, Sensitivity only affects the visual scaling. Use Sensitivity to calibrate the display to your environment, then Gain to fine-tune the input level.