Voltage Surges in Audio-Frequency Apparatus

Transient voltages of over 2000 are shown to occur across the secondary when the normal plate current of a high inductance audio transformer is opened. The oscillograph and inverted vacuum tube are used to bring out further that these transients are oscillations of definite frequency and magnitude, depending on the primary current, inductance, and secondary distributed capacity. The manner of breaking the circuit has a minor influence, for in most cases no appreciable discharge takes place at the contacts. The effect of amplifier circuits on the transients is considered, and suggestions are made as to possible means of protection.