Amp repair on premises. Rockin' Bob, is a master technician with over 25 years' experience in amp repair. We are one of the few qualified shops in the Boston area to offer guitar amp repair and we specialize in tube amps.New budget guitars for the beginning student. Used Sound is an authorized dealer for Johnson Guitar Company, offering an excellent line of acoustic guitars starting at $115.We Buy Guitars! Rockin Bob's Guitars buys guitars in good condition, and we accept trade-ins if you're making a purchase. We offer fair, Blue Book prices. Unlike consignment shops, we'll write you a check right away.