91A 300B Single Ended Mono Amplifier
THE CURIOUS DEVELOPMENT OF SINGLE ENDED POWER STAGE
At the origins of low frequency tube amplifiers, the mounting of a single tube was reserved to devices using simple and cheap materials .
By opposition the symmetrical mounting was meaning of perfection and therefore found only on performing and expensive equipment. It is interesting to note that this tendency is now quite opposite. This surprising result has various reasons one of them is described below.
1 – Poetical reasons
During the 70’s Japanese enthusiasts – passionate of music and technique – have discovered the qualities of an old “WESTERN ELECTRIC” apparatus. This talking picture amplifier designed for small movie theaters was fitted in its output stage with a single tube 300B (WE 91A).
The amplifier was not perfect but gave surprising musical results. The dynamics coming from this amplifier seems more potent than its modest rated power let suppose. Working on the matter by improving the power supply to reduce the ” hum “and using a bigger output transformer, our Japanese enthusiasts gave birth to a new range of High Fidelity single tube amplifier. We have to recognize that this amazing result was ,it seems,a real snook to the technical world.
From Monsieur Verdier