The Ruby Amp is a great little battery powered solidstate practice amp. The design is based on the Little Gem design which in turn comes from the Smokey Amp designed by Dave Stork on www.blueguitar.org. The design uses relatively few components and is a good DIY project. Cigar box guitar maker J.K. built a Ruby Amp but found himself hunting for a suitable enclosure for it.

The German based Behringer company designs and manufactures audio products, including public address systems, mixing consoles, amplifiers and audio processing units.  Their guitar gear includes a large range of stompbox effects, amplifiers, interface boxes and some guitars.