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Teensy 3.x Audio Adaptor Boards (Rev C)

This audio adaptor lets you easily add high quality 16 bit, 44.1 kHz sample rate (CD quality) audio to your projects with Teensy 3.0, 3.1, 3.2, 3.5, 3.6 (Rev C), or 4.0 (Rev D). The older versions can be used with Teensy 4.0 by wires or an adaptor PCB.

All versions of the audio shield support stereo headphone and stereo line-level output, and also stereo line-level input or mono microphone input.

The Teensy Audio Library lets you use the input and output simultaneously together with a toolkit of audio processing objects, to easily create all types of sophisticated audio applications. You can play multiple sound files, create synthesized waveforms, apply effects, mix multiple streams and output high quality audio to the headphones or line out pins.

Teensy 3.x have the Cortex-M4 DSP instructions which provide plenty of computational power for real-time FFT (spectrum analysis), opening up the possibility of creating advanced sound-reactive projects.


Function Teensy 3.x Pins
Rev C
Audio Data 9, 11, 13, 22, 23
Audio Control 18, 19 SDA, SCL (other I2C chips)
Volume Pot 15 (A1) -
SD Card 7, 10, 12, 14 MOSI, MISO, SCK (other SPI chips)
Memory Chip 6, 7, 12, 14 MOSI, MISO, SCK (other SPI chips)


Front Side
Rev C (for Teensy 3.x)


Back Side
Rev C (for Teensy 3.x)


Rev C (Teensy 3.x)



Audio Shield
Rev C
(Teensy 3.x)
Audio Master Clock, 11.29 MHz
Audio Bit Clock, 1.41 or 2.82 MHz
Audio Left/Right Clock, 44.1 kHz
DIN 22
Audio Data from Teensy to Audio Shield
Audio Data from Audio Shield to Teensy
SCL 19 Control Clock (I2C)
SDA 18 Control Data (I2C)
SCK 14 Data Storage (SPI) Clock
MISO 12 Data Storage (SPI) from SD/MEM to Teensy
MOSI 7 Data Storage (SPI) from Teensy to SD/MEM
SDCS 10 Chip Select (SPI) for SD Card
MEMCS 6 Chip Select (SPI) for Memory Chip
Vol 15 / A1 Volume Thumbwheel (analog signal)


The SD socket is accessed with 4 SPI pins. SCLK and MOSI are used at alternate locations. See the audio library examples for details on how to select these different pins. The SD card is useful for playing music. Sandisk and other good quality SD cards are capable of playing 2 WAV files simultaneously.

Wires for MCLK, BCLK, LRCLK, TX & RX should be kept short. The audio shield is meant to connect to Teensy through short pins. Wires can be used, but wires must be short to avoid problems.

The line in/out header uses a pinout compatible with the AC97 audio header on PC motherboards. The front panel cables from most PCs can be connected, or wires can be soldered directly to the pins.


Schematic, Rev C


In early 2019, a 100 ohm resistor was added to the MCLK signal.

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