Sugden A21 Series 2 amplifier

摘要

The late '60s provide an interesting choice of equipment for the vintage hi-fi enthusiast. The rapid development of high-quality transistor amplifiers during the period resulted in some intriguing models and the Sugden A21 is a fine example. Why? Because it was the first successful domestic hi-fi amp on the UK market to offer a fully transistorised implementation of Class A. To understand why this was a significant step forward it is useful to briefly remind ourselves what a Class A amplifier is. One key point to bear in mind is that amplifier classes are not intended to be hierarchical, despite their frequent misuse in advertising. The three basic classes - A, B and C (the latter not used in audio) -merely serve as engineering shorthand to describe the conduction angle of the valves or transistors in the amplifier's output stage and as such are not meant to denote an index of overall merit.