If there aren’t enough valves on your desktop then you’ll need a Vacuum Tube USB Speaker setup like this. It’s a USB 2.0 speaker, with a volume knob front-and-centre and 4 blue LED valves that pulse along with the music. It also has a couple of USB ports on the front and oodles of class. Works with XP/Vista or 7. About US$25 but you’ll have to get it through GeekStuff4U or another Japanese exporter.
Frequency: 100Hz ~ 10,000 Hz
Speaker diameter: 38mm x 2
Maximum output: 0.35W x 2
Maximum volume: 45dB
Vacuum tube design is strictly, not a real vacuum tube based.