Remarks on the Amplifier.

Radio Record, Volume II, Issue 13, 12 October 1928, Page 27

Remarks on the Amplifier.

({OMMEN TING on the performance ' of the moving-coil loud-speaker, a correspondent in a London radio journal, amongst other matter, gives the following remarks which appl) very much to all audio amplifiers :-"The push-pull scheme seems to bring out the low notes, though I am beginning to find that one has to go further back, and that the output stage is not the only one to bother about. The detector seems to have a marked effect on the performance, and I am just tackling this point now. It is really remarkable how one can go on improving the performance of the amplifier, and how this leads to discovering notes of which one was previously quite unconscious. An excellent test is the dance music. There is a drum or some such instrument which booms away more or less continuously, and which only begins to be really audible as one gets the amplifier working decently. If the average experimenter is not much more skilled than I am (an unfair suggestion, perhaps), and he perseveres with his amplifier, he will be astonished to discover what a large percentage of the music he has not been hearing. One hears of people obtaining excellent results by the use of one D.BE. 5A as an output valve. The only conclusion I can come to ‘s either that there is something very wrong with my equipment or that anyone who is satisfied with D.B. 5A results has never

heard a speaker working anyt] ing like well." (The D.E.5 has an impedance of 8000 ohms.) .