Yamaha GA15II Guitar Amplifier. Our new twin channel GA15II amplifier was designed to be a perfect practice partner – and it’s great for backstage warm-up sessions too The compact and very light amp delivers serious clean, crunch and distortion sounds. A great headphones jack is also featured so you can practice in private. Like the GA15, but with a new design. Moreover, with an additional AUX in, it will enable guitarists to play along with MP3 players.