Instructions

The Raspberry Pi has an on-board audio jack, which is super handy for all kinds of sound effects and speech, just plug and go! However, for when you want better audio for music playback, a USB audio card can greatly improve the sound quality and volume, this tutorial will show you how.

This guide will also show you how to record audio via the headphone jack on the adapter

Pre-requisites

First up, you will need a fully set up Raspberry Pi that is otherwise working and you can log into. We have tons of tutorials on that front, so get your SD card loaded with Raspbian (that's what we're using in this tutorial), and either ssh in, log in with a monitor and keyboard, or a USB console cable
Just a reminder, this tutorial is only known good for the USB audio card in the Adafruit shop. Audio cards all use different chipsets so if you have another card, it may not work here! You'll have to figure out what's different for your model.

Figure out your chipset

Figure out your chipset


Start by having your Raspi turned off/shutdown (perform a clean shutdown!) and then plugging in your USB audio card. Then boot the Pi as normal.

Once you log in, type dmesg | grep cm109 to look at the boot messages. You should either see some lines about cm109 if you have a CM109 chipset

raspberry_pi_grepcm109.png

or if nothing comes up, try dmesg | grep Headphone you will see the C-Media USB Headphone Set driver. This means its a CM-headphone
or if nothing comes up, try dmesg | grep C-Media you will see some C-Media notes but no mention of the cm109 driver. This means its a CM108

CM108 Type

If you have CM108


If you type in lsusb you should see a reference to C-Media Electronics, Inc. CM108 Audio Adapter
We'll need to update the firmware, this requires Internet access but only takes 15 minutes or so. You might want to run sudo apt-get update first if you haven't lately. Then run the following commands in order:
sudo apt-get update
sudo apt-get upgrade
sudo reboot
Now you can go down to the update alsa module options section

CM-Headphone Type

Type dmesg to look at the boot messages. You should see a bunch of lines that talk about C-Media USB Headphone Set
And if you type in lsusb you should see a reference to C-Media Electronics Audio Adapter but no mention of CM108 and the VID/PID is 0x0d8c:0x00c
Nothing special needs to be done! Hurray! Continue on to the Updating ALSA Config section

CM109 Type

Type dmesg to look at the boot messages. You should see a bunch of lines that talk about cm109
And if you type in lsusb you should see a reference to C-Media Electronics Audio Adapter but no mention of CM108
Nothing special needs to be done! Hurray! Continue on to the next section

Updating ALSA Config

Raspbian Jessie - Updating alsa options

All we have to do is tell Raspbian to look at "card #1" for the default audio. Card #0 is the built in audio, so this is fairly straightforward.

run sudo nano /etc/asound.conf and put the following in the file and save

pcm.!default  {
 type hw card 1
}
ctl.!default {
 type hw card 1
}

This will make the default PCM (audio) output card #1 and the default control also card #1

Raspbian Wheezy - Updating alsa options

If you're using Wheezy, we'll edit the audio system configuration file with

sudo nano /etc/modprobe.d/alsa-base.conf

For all but the most recent Raspbian Wheezy releases, look for the line that reads:

#options snd-usb-audio index=0

Change this to:

options snd-usb-audio index=0

Note we removed the # at the start of the line.

For the latest Raspbian Wheezy versions, look for this line instead:

options snd-usb-audio index=-2

There's no # to remove in this case, just change the index from -2 to 0:

options snd-usb-audio index=0

Testing Audio

Testing!

OK now that you've configured ALSA depending on your OS...that's it! Now reboot with sudo reboot and log in again, you can test with speaker-test by running

speaker-test -c2

Which will play white noise through the left and right 'speakers' on the audio card. Once you've got something coming out, try to play an audio file with speaker-test (for WAV files, not MP3)

speaker-test -c2 --test=wav -w /usr/share/sounds/alsa/Front_Center.wav

If you want to play a stream of music, you can try

sudo apt-get install mpg123
mpg123 http://ice1.somafm.com/u80s-128-mp3

If you want to play MP3's on command, check out this tutorial which covers how to set that up

Headphone vs Audio card

Don't forget, you still have the built in headphone jack on the Pi, if you edited alsa confit might be called card 1 now (not the default card 0)

You can run aplay -l to list the devices

If you want to aplay through a specific card, specify card 1 with -D plughw:1,0 or card 0 -D plughw:0,0 etc

speaker-test -c2 -D plughw:1,0

aplay --device=hw:1,0 test.wav

Setting Audio Levels

You can set audio levels for both output and input with

alsamixer -c 1

Use the arrow keys and return/escape to set and save the settings. It's a sorta-cute text-graphics system

Recording Audio

At least with the CM-Headphone type adapter, you can also record audio.

 arecord --device=hw:1,0 --format S16_LE --rate 44100 -c1 test.wav

Will record signed 16-bit (S16_LE) audio at 44100 Hz (--rate 44100) mono (-c1) audio to test.wav. We've noted that any audio input will be echoed out the speakers as well

You can have a little VU meter show up if you add to the-V mono command line. Press control-C to quit

Once you're done recording you can play back with

aplay --device=plughw:1,0 test.wav

Troubleshooting!

If you're using a Raspberry Pi and notice the output isnt totally clean, some USB Audio adapters don't like USB-1.2 and produce crackling in the output. You can work around the problem by adding dwc_otg.speed=1 to /boot/cmdline.txt and setting the USB ports to USB-1.1 mode.

You can get user access to the audio hardware with other devices by granting access using sudo usermod -a -G audio username