文档介绍：ETI 1981 & Electronics Digest Winter 1985
60W Class-A Amplifier (part of the ‘System A’ series of articles)
By Stan Curtis
Class A Power
There is one amplifier configuration that is universally accepted as the ideal for audio use: Class A
operation. Many early amplifiers operated in Class A, but as output powers rose above 10W the
problems of heat dissipation and power supply design caused most manufacturers to turn to the simpler,
more efficient Class B arrangements and to put up with the resulting drop in perceived output quality.
The System A applies the unchallenged excellence of Class A operation to the design of a reference
amplifier free of the aberrations mercially available models. Class A biasing is recognised as the
ideal operating mode for an amplifier, offering the promising accuracy demanded by dedicated
audiophiles. The superiority of this amplifier depends on the output devices being constantly operated in
their linear region, above cut-off and below saturation. Such operation results in the smoothest transfer
function and the widest bandwidth.
The System A amplifier has a clarity and a tonal response that produces a superior perspective of depth
with a sense of reality: instruments appear in precise position out of a silent background. The musical
' naturalness' of isth amplifier is due to its lack of the con