Diamond shows $40 external sound card with volume knob
 

A good sound card is kind of a must if you have half-way decent analog speakers or headphones. But not all systems have room for a PCIe sound card—especially microATX and Mini-ITX builds. That's where Diamond's new Xtreme Sound 7.1 USB audio box comes in.

http://techreport.com/news/25897/dia...th-volume-knob