Notes on the Testing of Audio Frequency Amplifiers

The more necessary of the various points which must be tested in examining the performance of audio frequency amplifiers are outlined, and a method of test procedure, found by the author to have desirable characteristics from the points of view of accuracy, speed, and simplicity of operation, is described. The method used permits the complete curve of amplification vs. frequency for the amplifier under test, to be drawn directly by the test equipment in a very short time. A type of tube voltmeter found convenient for measurement of amplifier output potential is described. Brief discussion is given of the testing of individual audio frequency amplifying transformers, and some test methods applicable thereto are suggested. Amplifier wave form distortion, and overloading are discussed, and methods for the test thereof are recommended.