16 watt amp:

click here to enlarge schematic

parts:

U1 U2	LM383 8 watt audio amplifier ic
R1, R3	220 ohm resistor
R2, R4	2.2 ohm resistor
R5	1 megohm resistor
R6	100k audio taper potentiometer
C1, C7	10uf electrolytic capacitor
C2, C5	470uf electrolytic capacitor
C3, C4, C6	0.2uf ceramic capacitor
SPKR1	4 to 8 ohm speaker (up to 8 inches diameter)

all resistors are 5 or 10 percent tolerance, 1/4-watt
all capacitors are 10 percent tolerance,
rated 35 volts or higher

this circuit provides 16 watts of amplification. it is built using two LM383 power audio amplifiers. use suitable heat sinks with the ic's.