Crystal oscillator with a 6A6 (T437E)

We found this circuit with the 6A6 double triode in a 1938 Radio Handbook. The power source is not provided.

RIAA Equalizing Preamplifier (CB4947E)
Indicated for vinyl media recovery, this circuit is from the 80's, having been found in an...
500 MHz Probe (CB3918E)
This circuit is intended for use with common oscilloscopes having been found in documentation on...
BCD to Analog Converter (CB5091E)
This circuit can function as a simple shield converter from BCD to analog outputs. The circuit...