This guy also built and open-sourced a universally admired headphone amplifier and DAC.<p>His O2 amp: <a href="http:&#x2F;&#x2F;nwavguy.blogspot.bg&#x2F;2011&#x2F;07&#x2F;o2-headphone-amp.html" rel="nofollow">http:&#x2F;&#x2F;nwavguy.blogspot.bg&#x2F;2011&#x2F;07&#x2F;o2-headphone-amp.html</a><p>His O2 DAC: <a href="http:&#x2F;&#x2F;nwavguy.blogspot.bg&#x2F;2012&#x2F;04&#x2F;odac-released.html" rel="nofollow">http:&#x2F;&#x2F;nwavguy.blogspot.bg&#x2F;2012&#x2F;04&#x2F;odac-released.html</a><p>JDS Labs and others sell them commercially for those who don&#x27;t feel like building them by hand.