This circuit was published in a 90s Radio Electronics. The circuit uses the well-known LM386 that appears in a large number of projects on this site.
This is the basic operational amplifier configuration for gain 10. R2 can be changed to other...
This circuit uses a capacitor that depends on the frequency of the crystal. We found it in a 1967...
The crystal frequency of this circuit found in an American documentation is limited only by the...