Here's an interesting tube power amplifier circuit for automotive use. It can be used in advertising or notice or other mobile applications.
In this application high voltage is obtained by a vibrator, which consists of an electromechanical system which was employed in the valve of car radios 40, 50 and 60. This circuit has a blade which rapidly vibrating generate a low pulsating voltage in a transformer, powering thus the high-voltage circuits for the valve.
In modern circuits this vibrator would be replaced by a high-voltage DC/DC converter. The high voltage is obtained from a special transformer and two rectifier valves 6X5.
The input sensitivity to a microphone is 4 mV. For pickup is 200 mV. The consumption of this circuit is 6 V and 8 V at 12 A.
In addition to the valves, the critical components of this project are the transformers. Figure shows the complete diagram of the amplifier.
