So I got HeadRoom’s “Total Bithead” USB DAC (digital-to-analog converter) and micro amplifier. The problem is, when I plug it into my Linux desktop, mplayer/firefox still recognizes the onboard sound on my motherboard as the default device. After some searching, I found some resources to (1) use it as the default sound device and (2) enable mixing on it (different applications can simultaneously use the Total Bithead).
The Setup
We need to manually call a script every time the Total Bithead is
connected. The script, called switch_audio.sh, looks like this:
#!/bin/zsh
if [[ -e /proc/asound/card1 ]]; then
ln -sf ~/syscfg/alsa/cfg-total-bithead ~/.asoundrc
else
case $HOST in
k0) ln -sf ~/syscfg/alsa/cfg-k0 ~/.asoundrc ;;
k1) ln -sf ~/syscfg/alsa/cfg-k1 ~/.asoundrc ;;
*) echo "Unknown host \`$HOST'" ;;
esac
fi switch_audio.sh [GitHub] [Download]
where k0 is my desktop and k1 is my laptop. cfg-k0 looks like this:
# use `aplay -l | awk '/^card/{print$3}' | sort | uniq' for card names
defaults.pcm.!card NVidia
defaults.ctl.!card NVidia
defaults.pcm.!device 0
defaults.ctl.!device 0
and cfg-total-bithead looks like this (yes, the Linux kernel
recognizes the Total Bithead as CODEC):
defaults.pcm.!card CODEC
defaults.ctl.!card CODEC
defaults.pcm.!device 0
defaults.ctl.!device 0
That’s all there is to it. Now every time you plug in/out the Total
Bithead, just run this script. You could do some fiddling with udev or
some other low-level mechanism to automatically run the script when it
detects the Total Bithead plugged into a USB port, but I’d rather just
call it from a keyboard shortcut manually each time for explicit
control. The ~/.asoundrc configurations are taken from
this helpful blog post. It’s pretty sad that the 4-liner ~/.asoundrc
solution offered from that blog remains unknown to all the
mplayer/alsa/linux wikis out there on the web. The setup here takes care
of multiple applications playing sound simultaneously.
Other Thoughts
I got the Total Bithead used for around $50. From what I can tell, it first appeared in the market in 2004 (there’s a review of it dating back to that time). I do recommend it at this price point when comparing it against the newer Realtek HD audio chips found in most modern motherboards. Don’t buy a new one for over $100; it’s probably much better to just get a better pair of headphones with that amount of money.
