The integrated circuit of this amplifier is not very common today. The output transistors can be TIP31 and TIP32 in heat radiators. The circuit is from the 1977 National Semiconductor Audio Handbook.
This circuit uses a sensitive 9V relay but can be built with 6 or 12V relays by changing the power...
This ultra-simple adjustable power source is of great use on the bench of any electronics...
This high-power flasher for incandescent signaling lamps was found in a 1980s General Electric...