We found this circuit in a documentation for radio amateurs from the 70s. The transistors can be the BC548. With it, small speakers of 4 or 8 ohms can be used as microphones.
I found this circuit in an Electronics Handbook from 1989. The circuit can be assembled with a...
The TDA2613 is the mono version of the TDA1521A and has pinouts compatible with an integrated...
This sound effect circuit uses only one integrated. We found it in a 90's EDN. The effects can be...