Andy, thats why my question was asked!! I usually see one resistor per output bottle.
BUT at the same time with very neat layout and short wiring and specifically grid drive leads, they can be gotten rid of. I have built a very similar amplifier using 807's, and they were not needed, but then again that design was extended class A, one valve wired as a triode, and the other as a tetrode on each side of the centre tap. I don't think the pots will fail ( he said, and held it to the light) they are beautifully made 2 watts. Bias pot is 5 watts and the balance pot in the cathodes is huge 25 watts with a large carbon brush that operates on the winding ( see previous picture).
This is my first build using 5B/254 aka CV 428, so I am just treading gently. I have 50 of them, so I will be able to balance them I think. I get them for a few dollars each, and there are a few thousand available. I can also get 5B/255 aka CV391, which are "identical", but without topcap, the plate being taken to the valve base, namely pin 2.
They are more expensive however, as the guitar amp builders replace the famous RCA blackplates with them. ( RCA blackplates now fetch about $250 dollars each!!!!!!
).
Thanks for the compliment Al, what I meant about 3mm is the diameter of the hole I drill first as the pilot hole, I then scale up as I go. Chassis material is 1.6mm thick "zincalume" steel. Zincalume is electro plated mix of aluminium and zinc that can't be soldered. It also doesn't rust, even after years in the weather. I use a jig saw to cut the transformer drop throughs, a mm or so smaller than it needs be, and then file finish them. In fact I don't have drills the right size for valve bases either, so they are filed up to size too. I still have blisters healing on my fingers from the filing
.
WE had 4" of rain overnight ( the first "wet season" rain in about 20 years) so painting will have to wait untill the 90% humidity goes. I will keep you all posted.
Regards, Joe.