EL84

The EL84 is a small-signal power pentode vacuum tube. It was first introduced by Mullard in 1953 and quickly became popular for its compact size and relatively high output power for its class. The EL84 is commonly used in audio amplifier circuits, particularly in guitar amplifiers and hi-fi systems, where its warm and harmonically rich sound is often prized. Its characteristic curve allows for significant distortion at higher signal levels, which can be desirable for musical applications. The tube typically operates with a plate voltage around 250-300 volts and a screen grid voltage of similar magnitude, drawing around 50mA of plate current. It has a cathode bias resistor that is crucial for proper operation and to prevent thermal runaway. Variations and direct equivalents include the 6BQ5, which is the American designation for the same tube. Despite the widespread adoption of solid-state technology, the EL84 remains a popular choice for vintage-style audio equipment and for builders seeking its distinctive sonic qualities.