I have finished my newest DIY amp. Sadly no headphone connect (yet?). I bought Russian 6F6S tubes because of this effect.
With 6F6S's around 2x13w triode connected and pentode connected 2x18w. So these small powertubes are giving their max. Of course this amp is designed for KT88's, and with them i get much more power. And here is the amp with 5U4G, 4 6F6's, 2 6SN7 and 12AV7.
I had so many different 12A*7 tubes from little dot times, so decided to use these as driver tube and they tolerate more voltage than 6DJ8. Transformers and choke are from old Hammond organ amplifiers. 4 inputs and again selector switch from old organ, since it was way better quality, than new small plastic knob. 6SN7's are connected as long-tailed-pair phase inverters. There is small switch for triode-pentode change behind powertubes. It seems to be mostly as for experimental and not for real high-end sound with pentode connection.
Amp size is 50x37cm and weights 20kg.