Short for Vacuum Tube
, a device used to drive amplifiers until the advent of transistor
s. A tube works like a flood gate, except with heat. A small heater
in the base warms up, while a gate like mechanism opens and closes depending on the input signal. As heat goes through the "gate", it is turned into electrical energy. Tube slots must be biased
, which determines the voltages seen by the tube. Only guitar amps still use tubes (as well as some bass amps, mic preamps, and other pro audio devices.)
Though a true discussion of tubes is enough to fill a large book, let alone a short definition, but here are some more common types of tubes.
Preamp: American name (European name) Other name
12AX7 (ECC83) 7025