This harmonic oscillator controlled by crystal was found in an American documentation of the 90's. The circuit uses transistors of the time. Current equivalents can be used.
The figure shows an application of the LM377 in a small inverting stereo amplifier with output...
This 500 MHz oscillator has an output power of 1 W when powered by a 20 V source. The circuit was...
We can use this amplifier with low impedance headphones with good performance. Possible...