Using LM386 voice audio power amplifier circuit designed for use in low voltage consumer applications can be designed a very simple voice amplifier with variable gain and volume control.
Using TDA2003 audio amplifier integrated circuit can be designed a very simple 10 watts power audio amplifier on a 2 ohms load or 4 watts on a 4 ohms load .
using the LM3915 monolithic integrated circuit can be designed a very simple audio power level meter that senses analog voltage levels and drives ten LEDs, LCDs or vacuum fluorescent displays, providing a logarithmic 3 dB/step analog display.
