THE POWER VALVE

Radio Record, Volume I, Issue 25, 6 January 1928, Page 15

THE POWER VALVE

A DXHSiRABLE ADDITION. Although many different kinds of power amplifier valves have been ou the market for some years, it is surprising how little these valves are used by broadcast listeners. It may be that this is because the cost and the current consumption of power amplifier valves are higher than those of the average general purpose valve, but nobody who has used a power amplifier will question that the extra first cost and oper-. ating cost of the power amplifier is justified by results. Power amplifiers are intended for use in the final socket of a receiver designed for loudspeaker operation, They ate designed to handle a greater undistorted output than an ordinary valve, and they should always be used when fairly loud signals are required. In many sets, from: which. signals are not very loud and frem which loud signals are not desired, the power valve will not make any great imcrease in the volume of sound when it is used, but it will nearly always effect a marked improvement in the purity of the music from the receiver. The extra cost of the power valve is largely offset by the fact that its life is longer than that of an ordinary valve. It is desirable to. use a separate B battery plus connection to the power valve, so that a much greater voltage can be applied to it than that used on the first audio valve. A "€" battery connection is also necessary.