The 6BA7 vacuum tube is a miniature medium-mu dual triode amplifier or preamplifier tube. It belongs to the 12A_7/12B_7/6A_7 family of audio-frequency double triodes, and is an upgraded version of the 12A7, with an increased amplification factor or mu. It was introduced in the 1950s and continued in production until the mid-1970s, when it was replaced with more durable and cost-effective transistors. Like its predecessor, this tube is often used in amplifiers and preamps in the audio frequency range, as well as in tuners, radio transmitters, and other preamplifier circuits. Its features and parameters make it an excellent choice for boost and tone coloration.