ABSTRACT
This chapter covers the vacuum tube line-stage amplifiers design. Owing to a lack of complementary vacuum tubes, designing vacuum tube amplifiers is different from solid-state amplifiers. Fortunately, most vacuum tubes used in line-stage amplifiers are triodes, which have high linearity and low distortion. As a result, employing only a few pieces of triodes produces a highly musical line-stage amplifier. The chapter starts with the classic Marantz 7 amplifier design, which contains three stages with the use of negative feedback. Then unbalanced input–unbalanced output line-stage amplifiers employing single-stage compound amplifiers and two-stage amplifiers, without using negative feedback, are discussed. They include SRPP, half-mu, Aikido Wing Chun, Tai Chi, cathode-coupled, and cathode-coupled push–pull amplifiers. Finally, several fully balanced vacuum tube line-stage amplifiers are discussed. The vacuum tubes discussed in this chapter include 6H30, 6922, 6N1P, 12AU7, and ECC99.
