Do the filaments light when the unit is on? Yes, the tubes are light up
Is the source sending signal? Plugging the headphones directly in the 1/4 plug in my computer sound card, it works
Is the input selector switch in the back in the appropriate position? Yes, and I've tried them all *just in case*
ie. RCA for RCA input, USB for USB input? If it is in D/A position, it will turn the RCA connectors into OUTPUTs from the internal DAC.
As RCA, I did try the two playback methods I can see on my sound card : Speakers (Sound Blaster ZxR), and Digital Audio (S/PDIF) (Sound Blaster ZxR DBpro).
As USB, I installed the drivers and set playback to Speakers (USB2.0 High-Speed True HD Audio).
Either I'm doing both of them wrong, or there is something else wrong.
No need to press on the tubes at all right? Right now they are pretty much "loose". The "head" of the tubes are about 1cm below the glass.