Balloon 3 Audio
There are various audio options dependent on parts fitted, and which connectors you use. Balloon3 can be configured for 2 line inputs, one line and one microphone input, or one microphone input only if J16 is used for audio in. Stereo headphone out is always available.
J10 has the raw audio signals available: audio in L&R, audio out L&R, as well as a range of other codec signals. J16 has the signals pass through some filter components which is how the line/mic options and characteristics are set. So J16 is normally used for audio in/out as no other components are needed.
On E1 boards inductor L5 (0.1uH) is often not fitted - this provides power to the Audio codec so nothing will happen without it. Ensure you have one before trying to do anything with sound. It is near the main power connector J1:
The mic/line selection components (C136, C137, C139, R38) are all on the back near the audio connector J6, and are labelled.
and for convenience (so the old /dev/dsp interface works) usually
modprobe snd_pcm_oss modprobe snd_mixer_oss
apt-get install aumix madplay
Run aumix to set output level (v is volume, w is pcm, S means save to make default)
aumix -v 100 -w 100 -S
copy over an mp3 and then play it.