We found this circuit in an English publication from the 1980s. The circuit uses current components and can be tuned for frequencies between 300 and 1500 Hz.
This is one of the many approaches we have on the site for this low power 0.5 W amp using the...
This circuit of a 1969 Electronic Design uses RTL logic. The setting can be adapted to TTL. The...
This circuit was obtained in a 1979 publication but can still be easily assembled today by...