Glassfet is jargon for vacuum tube. Vacuum tubes, consisting of electrodes enclosed in glass envelopes from which most of the air has been pumped out, are no longer used in computers, having been replaced by transistor s in the 1960s and by integrated circuit s in the 1970s. The term glassfet arises from its similarity in pronunciation to GaAsFET, which is an acronym for gallium arsenide field-effect transistor. GaAsFETs have high impedance, a characteristic that they share with glassfets. But in other respects, the two are vastly different. GaAsFETs work with low voltage s, while glassfets operate with high and often dangerous voltages. Most GaAsFETs consume little power, while glassfets consume large amounts of power. GaAsFETs are tiny and light, but glassfets are large and massive. GaAsFETs are physically rugged but electrically fragile, while glassfets are physically fragile but electrically rugged. Vacuum tubes, while considered obsolete by some electronics enthusiasts, have enjoyed a resurgence in recent years among audiophiles, particularly those who build amplifier s for popular music bands. Some musicians believe that vacuum tubes produce sound with better fidelity than transistors when peak audio power levels must be high (in the kilowatt range or greater). Vacuum tubes are still used in some high-power, high-frequency radio broadcast and radar equipment