The goal of this tutorial is to play a wave file stored on the SD card using the new Audio lilbrary and the 10 bit DAC.
Components to build an external audio amplifier
To connect a speaker to the board you have add an amplification circuit connected between the DAC0 pin and the speaker. The amplification circuit will increase the volume of the speaker. There are many audio amplifiers available, one of the most common is the LM386.
The following scheme shows how to build the circuit using the LM386 and a bunch of components.
You can supply the LM386 connecting the Vs pin with different voltages sources, like for example the +5 V present on the 5V pin of the Arduino Zero / MKRZero or an external 9V battery.
The gain of the amplifier is given by the capacitor connected to pin 1 and 8 of the LM386. With the 10 µF capacitor the gain is set to 200, without the capacitor the gain is 50.
With the potentiometer you can control the volume of the amplifier.
LM386 electronic schematic
For Arduino Zero and MKR1000 you need to connect shield or module for an SD or microSD card with CS on pin 4.
LM386 mounting on breadboard
For MKRZero, the microSD Slot is built in. A .wav file named "test.wav" is in the card's root directory. For a simple test you can attach a pair of headphones directly to ground and DAC0, respecting the polarity.
The same circuit made with MKRZero and all the components on a single breadboard
Warning: do not connect the speaker directly to the pins of the Arduino Zero or MKRZero.
The Audio file to store on the SD card must be in the .wav format with 88200 Hz, 8-bit unsigned PCM mono quality. This type of file can be easily obtained using audio programs like audacity.