Blast from 1969: About Power Amplifiers – Valve or Transistor?

This is the text of an advert taken out by Radford in HFN in 1969

About Power Amplifiers – Valve or Transistor?

If you are about to purchase a high quality amplifier, the question – Valve or Transistor type? – is bound to arise. There are too many parameters to equate and too much conflicting hearsay to make the answer clear cut. However difficult the purchasing problems may appear to the discriminating buyer, the problem facing the manufacturer of valve amplifiers, jealous of his reputation in respect of performance and reliability, is even greater.
Let’s face it. Generally speaking transistor power amplifiers have not turned out to be quite what we were led to believe. We have found all manner of faults and snags in practice which were not envisaged. Omitting such objectionable characteristics as blowing up when the output is short circuited, what is basically wrong?
In the main, transistor amplifiers sound different from valve amplifiers, and produce listening fatigue. This we believe to be due to some design inaccuracies, but fundamentally to the use of the high power-efficiency class ‘B’quasi-complimentary circuit. This circuit inevitably produces a large amount of distortion by class ‘A-B’ valve standards.
The reasons for this will be given in an article to be published later. Simple harmonic slope distortion can be reduced by negative feedback but the effects of crossover distortion cannot. Have you noticed that in most transistor amplifiers the measured harmonic distortion does not decrease linearly with output? The most significant observation is, however, that the amplifiers sound far worse than measurements indicate when compared with valve amplifiers.
Good transistor amplifiers can be made, of course, but the disparity in price to performance ratio when compared with valve amplifiers has been too great to ignore except for professional users.