EL84

Article summary

The EL84 is a vacuum tube of the power pentode type. It is used in the power-output stages of audio amplifiers, most commonly now in guitar amplifiers, but originally in radios. The EL84 is smaller and more sensitive than the octal 6V6 that was widely used around the world until the 1960s. An interchangeable North American type is the 6BQ5 (the RETMA tube designation name for the EL84). The EL84 was developed to eliminate the need for a driver tube in radios, so it has rather more gain than is usual in a power pentode. Eliminating a preamplifier triode in radios made them cheaper. Manufacturers were quick to adopt it in general use, and they are found in many old European tube-radios and other audio equipment. A single EL84 was used in low-cost equipment, and a push–pull pair for lower distortion and higher power. In common with all 'E' prefix tubes, using the Mullard–Philips tube designation, it has a heater voltage of 6.3V. It can produce 17W output in Class AB1 in push–pull configuration. Many guitar-amplifiers routinely run EL84 tubes in excess of 400VDC, with the Traynor Guitarmate reportedly putting out 25W (average) with 2 EL84s in a push–pull configuration and a B+ between 400 and 420 VDC.…

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