Carlsbro SHERWOOD 20R Acoustic Amplifier Carlsbro SHERWOOD 20R Acoustic Amplifier. The Carlsbro Sherwood 20R is a 20-watt acoustic amplifier designed for solo artists performing in small venues, practicing at home, or busking. It features a 6.5-inch full-range speaker and offers both a 6.3mm jack input for guitars and an XLR input for microphones, accommodating simultaneous [...]