ES-11    1 Watt General Purpose Miniature Audio Power Amp
(DC 3 ~ 15V) 

A battery-operated audio power amplifier that uses the popular TBA820M one chip audio power amp. IC.  Can be easily adapted to many applications like Walkman amplifier or signal tracer. The actual output power depends on the supply voltage & the impedance of the speaker used.     (2  1/4  inch 8 ohm  speaker NOT  included)    

               Click here for  TBA820M datasheet (pdf)