I was interested in the magic eye valves after seeing a Logic 3 valve 80 ipod docking station.  After an ebay and google search I was a bit put off as so far I have stuck with low voltage things and this valve needed a voltage around 250V to work.

Granted it does nothing to the sound but I kind of like the visual effect in a sad disco light for one kind of way so when I found this PCB board plus tube which worked with a 12V DC supply I gave it a go (currently reduced to $23.92 and free shipping)

http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=110932800502

This is a video of what it looks like (not by me)

https://www.youtube.com/watch?v=ahwbbuJ-DtM

It was very well packaged - bubble wrap within a sealed polystyrene box and I gave it a quick try yesterday with a 12v battery for the PCB using a mains 20W amp (which has a separate output for an external speaker) as the signal source and just connecting the input and common ground (with the battery) on the PCB with test leads to the signal to the speaker and it works well.

I could only find 1 cheaper PCB on ebay, but although it looks the same it doesn't contain the tube as well so at present this is the best deal I could find.

Please note the PCB does contain the circuit to step up the voltage to 255v as shown by another seller here http://www.ebay.co.uk/itm/6E2-EM84-EM87-EM800-6HU6-magic-eye-indicator-tube-vu-meter-pcb-assemled-gold-pl-/190732781936?pt=Vintage_Electronics_R2&hash=item2c688f4970 so if you want a sad disco display for one be careful where you stick your fingers :O)