This simple general-purpose transistor mixer was taken from an article in Electronics Now magazine in March 1994. You can choose a low-noise transistor such as the BC549.
This circuit found on a William Sheets can be used with a headphone or external amplifier. The...
In the figure we have the circuit of a complete audio generator using the 741. The circuit was found...
This monostable multivibrator with signals in phase opposition was found in October 1986 Radio...