Using the Total Bithead with ALSA on Arch Linux

2013-01-12*
linux, sound, alsa, arch, hardware

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:

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#!/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

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.