The TPA is a twin channel (6W+6W) audio amplifier allowing the use of two speakers, one channel is dedicated to play the engine sound and the other to play all the sound effects. Both channels have a separate volume control for fine level adjustment.
Note latest version has a revised amplifier chip with built in heat sink which no longer requires external heat sink under normal operation.
WARNING the amplifier will get hot during use. It has built in thermal shut off to protect it from damage from excessive heat build up.