Found in an 1868 Mullard documentation this circuit has a dynamic range of 10 Hz to 25,000 Hz. Modern equivalent transistors can be used.
This circuit was found in 80's Popular Electronics. Transistors are commonly used. The...
This low current source uses some components that are hard to find in ours. The transformer is a...
This circuit is from a manual based on information from Japanese components from 1981. The power...