Triode Valves - Fewest Electrodes For Purest Sound.
The Triodes described on this page are PX4, PP3/250, ACO44, 4XP, AC/P1, PX25, PP5/400, PA20, 2XP, ACO42, 2P.
Right from the first radiogram manufactured in 1929, to the last radiogram in 1952, triode valves were utilised by R.G.D. There were exceptions, televisions did not feature triodes after WWII, and in 1939 the top of the range radiogram utilised tetrodes (though some lower in the range still used triodes). But generally the triode valve was the output stage of choice. Why? - the purest sound results from the least interference to the signal being amplified, and the device that performs this function beautifully is the triode valve.
R.G.D. usually incorporated triodes supplied by Mazda, namely AC/P1, PA20, PP3/250, PP5/400. Other manufacturers produced similar equivalent products that may be interchangeable, for example PP3/250 may be substituted by PX4. Some triodes that may possibly be found in an R.G.D. receiver are shown below.
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