This shot was inspired by and dedicated to samwibatt who seems to love older technology and Nixie tubes.
Tubes glowing in a Stromberg Carlson 50 Watt rms audio amplifier. The sweet hum of mellow tube amplified sound. Normally tubes don't glow blue like this when they are in normal operation mode but these are very old and fairly gassy -- thus the blue plasma glow inside. The amp was also running full out with no load which also adds to the glow.