Hi Steve, Ali here, nice to see you here.

I recognise that wallpaper

afternoon squire, seems nice here and the screen is pretty

You know that old army command

"1 step forward all those who can play the piano"

and everyone else takes a step back


that leaves you in the welcoming position 

Oh yes and you can type the smileys too 

Yep...I like valves

Seriously though, the amp is all pentode, which means that I needed 2 regulated screen supplies; one for the input valves and another for the output valves.

The set of 5 valves on the left of the chassis are all to do with the power supply and screen regulators.
Largest one is a 5U4G rectifier valve used as a soft start element for the audio circuit.
The heaters are allowed one minute to warm the valves through, after which a delay relay closes, firing up the soft start valve, which brings up the 500V HV supply nice and gently.

Nobody builds all pentode amps anymore. Only the guitar amp guys build pure pentode output stages. Everybody else building hi-fi pentode push-pull amps uses triode inputs, phase splitters and drivers feeding output stages set up in ultralinear configuration. This drastically reduces costs over pure pentode. Being a DIY'er, I don't have to worry about costs and as such can build these pentode things. The fact that they sound so superb and kick serious booty, is an added bonus. 

Yep...EL84 is my preferred valve for lower power amps. It just does everything right and is easy to drive.
For higher powers, I love the EL34.
I did have a longish love affair with KT120s, but though they seem to give more in hi-fi terms, they just don't do it on a musical level; not for me anyway, though YMMV as ever.

Indeed