This symmetric 30 mA x 15 V power supply was found in the Ferranti transistor manual from 1974. Transistors are common types at the time.
This configuration of PWM control with the LM317 was found in a Popular Electronics from the 90s....
This 3 V rail to rail buffer was found in a National Semiconductor documentation. The gain is unit....
We found this traditional low-frequency filter setting for turntables in the 1977 National...