120W power amplifier
http://xedox.de/verstaerker.html
uses a dual 20 Volt power supply and delivers 15 watts RMS into an 8 ohm load.
http://www.zen22142.zen.co.uk/Circuits/Audio/amp15.htm
7 type of vaccumtube amplifier. 6AW8A is the best tube to the audio amplifier of amateur radio. 38dB is best gain of all the circuits. 390mW is enough power.
http://www.intio.or.jp/jf10zl/7vac.htm
This circuit needs very big idle-current (=150mA), so it is not power-effective. But this machine acts as A-class-amplifier.
http://www.intio.or.jp/jf10zl/EF.htm
http://margo.student.utwente.nl/el/audio/pwramp01.gif
Here is a simple and cheap amp to make.
http://europa.spaceports.com/~fishbake/amp/ca100.htm