15kW HF PA - definitely not for a QRP man!

A friend sent me this link http://www.dc9dz.de/en/index.html which shows the design and construction of a 15kW HF PA circuit for the amateur bands based around the Eimac 4CX10000D valve. Although I have no real interest in very high power and I do not expect to hear this on the air (please no!), it is a rather elegant piece of radio engineering.