ESP32 DAC output is noisy or buzzes

The classic ESP32 has two 8-bit DACs, on GPIO 25 and 26. Add a filter and an amplifier, and do not drive a speaker directly.

What the message means

An 8-bit output is coarse and the pin has little current. Wi-Fi activity also adds noise through the supply.

Fix it in this order

Use GPIO 25 or 26 on the classic ESP32. Other chips may have no DAC.
Add a capacitor in series for AC coupling, and a small RC low-pass filter.
Use a small amplifier module to drive the speaker.
Keep the supply clean and add a capacitor near the board.
Turn Wi-Fi off while you test audio quality.
Use an I2S DAC module for better quality.

Why it happens

The classic ESP32 has two 8-bit DAC channels on GPIO 25 and 26, giving 256 output levels between ground and about 3.3 V. That is coarse for audio and the pin cannot drive a speaker, so the signal needs a coupling capacitor to remove the DC level, a filter and an amplifier. The ESP32-S2 has DACs on different pins, and models such as the S3 and C3 have no DAC at all.

Wi-Fi bursts draw current in pulses that ripple the supply, and the ripple appears in the output as a buzz. An I2S DAC chip has higher resolution and its own reference, which is why it sounds cleaner.

If you see this, do this

You see	Do this
Buzz that changes with Wi-Fi	Supply noise.
Very quiet output	Add an amplifier.

buzzer no tone, input-only pins.

Last reviewed: November 2026. These are the usual causes and the order that finds them fastest. Test on your own board; clones and cables differ.

Why this happens

The DAC on GPIO 25 and 26 turns an 8-bit number from 0 to 255 into a voltage between 0 and about 3.3 V. That gives steps of roughly 3.3 / 255 = 13 mV. For audio, steps that large add a hiss of quantisation noise, and the output has no filter, so the sharp steps carry high-frequency content that can sound harsh.

The pin also supplies very little current. A speaker connected directly loads it down and distorts the signal, and the output carries a steady DC level that a speaker should not receive. The result can be quiet, buzzing sound. Noise from Wi-Fi bursts on the supply adds a buzz that follows the radio activity.

How to confirm the cause

Output a steady value with dacWrite and measure it with a multimeter. A value of 128 should read about half of 3.3 V.
Look at the output on an oscilloscope, if you have one, to see the steps in a sine wave.
Turn Wi-Fi off and run the tone again. If the buzz goes, the supply or radio activity is the source.
Power the board from a different supply or add a larger capacitor near the 3.3 V pin and see if the buzz changes.
Connect through a capacitor to an amplifier module instead of a speaker and compare.

Worked example

This test writes a ramp on GPIO 25. 256 steps at 40 microseconds is about 10 ms, so the repeat rate is close to 100 Hz in practice (the loop overhead adds slightly). A filter of 1 kohm and 100 nF has a cut-off at 1 / (2 x pi x 1000 x 0.0000001), about 1591 Hz.

void setup() {}
void loop() {
  for (int i = 0; i < 256; i++) {
    dacWrite(25, i);
    delayMicroseconds(40);
  }
}

// AC coupling: 10 uF into a 10 kohm load
// cut-off = 1 / (2 x pi x 10000 x 0.00001) = about 1.6 Hz

Common mistakes

Connecting a speaker straight to the pin.
Using GPIO 25 or 26 on an ESP32 variant that has a DAC on other pins or none.
Passing the DC level to the amplifier without a coupling capacitor.
Expecting 8 bits to sound like a music player.
Running Wi-Fi at full activity while testing audio.

If this did not fix it

Ground loops between the board, the amplifier and the USB power source.
The amplifier’s own gain and noise, which can add more than the DAC does.
A move to an I2S DAC module if you need clean output.

ESP32 DAC output is noisy or buzzes: pins 25 and 26, filtering and amplifier