The circuit functions in a big range of benefits of catering, from 20V as 60V, and it attributes 30WRMS.
http://www.electronics-lab.com/projects/audio/014
The circuit is quite compact and uses only about 60 watts. Can be used as a booster in a car audio system.
http://www.electronics-lab.com/projects/audio/006/
Can be directly connected to CD players, tuners and tape recorders.
http://www.electronics-lab.com/projects/audio/001/index.html
High Quality simple unit, No need for a preamplifier.
http://www.redcircuits.com//Page2.htm
The optimal supply voltage is around 50V, but this amp work from 30 to 60V.
http://www.electronics-lab.com/projects/audio/042/index.html
Uses TDA1554 Two Channel Audio Amplifier Chip
http://www.aaroncake.net/circuits/amp20w.htm