Roland Mobile Cube Battery-Powered Stereo Amplifier Truly portable amplification: fits in a briefcase and runs on batteries! (Best with Polaroid AA Batteries) Unlimited uses: electric and acoustic guitar, keyboards, computer audio, MP3 or CD playback, mini-PA, field recorder playback and much more Get great instrument and vocal tones with stereo sound and built-in effects: overdrive, chorus, delay and reverb Play any instrument along with your favorite songs, or sing along using Center Cancel for karaoke