Simple Class A Amplifier and Modular Pre-amp J L Linsley Hood.pdf

Wireless World, December 1970 607 Simp le Class A AInp lifie r and Modular Pre-amp A postscript to designs published last year by J. L. Linsley Hood The author has had the benefit of an extensive and frequently helpful correspondence with readers following the publication of the two circuit designs: Attention has been drawn to some obscurities in the original articles and to certain possible improvements in the design. Details are given below. Class-A amplifier Power supply. Although much interest was aroused among constructors by the good technical (and audible) performance given by the amplifier, it is clear that the principal feature in the eyes of many users was the relative simplicity of the circuit. This being it must have seemed a pity that the power-supply unit was somewhat complex. However, the purpose of this power-supply design was to avoid possible degradation of the amplifier performance by . ripple. The sawtooth ripple voltage across the reservoir capacitor in a class-A amplifier drawing some 2-3 A will be many times greater than in a class-B system, particularly at the audibly important low-signal levels. However, a number of measurements have been made since the publication of the original article on an amplifier of this type, operated from a simple power supply unit of the type shown in Fig. 1. There is little differenc