This is the traditional audio preamp configuration with the National Semiconductor LM382. The circuit has good gain and can be used with magnetic pickups or from signals from an auxiliary input.
The Texas Instruments TPA3100D2 integrated circuit (www.ti.com) consists of an efficient class D...
This circuit was found in an American documentation on transistors from the 60's. The transistor is made...
Found in a Radio Electronics from the 90s, this circuit generates a 1 kHz signal to serve as a...