[joebog1]

Thanks for the answers guys,

I have made a couple more sketches showing what's in the power supply (without the inrush and primary circuits)and what's on the amplifier chassis.

REMEMBER !!

There are two identical circuits on the power supply chassis. There are of course two identical circuits on the amplifier chassis as it's a stereo system.

These additional drawings will make it a bit easier to visualize I hope.
My original question relates to the two capacitors in the top left of the amplifier chassis, so now you can see there are in fact 4 of the 100 uF 500 volt F&T capacitors, two on the power supply chassis, before and after the main filter choke, and the two under discussion on the amp chassis.

I have added the positive bias supply applied to the input valves, to reduce heater/cathode voltage, and I guess too, it will reduce hum to some degree.
The reason I have tied it to pin 9 ( centre tap of the heaters for each individual triode) is because it saves two resistors, and I figure that the two heater resistances within a single valve will be from the same production run of heater windings, and will be near as dammit identical, so the centre tap should approach the ideal.

I have another question though!! after reading up on gas regulators.
On the bias supply, which consists of the power components on the power supply chassis, and includes the OB2, then, via the umbilical, there is a 50 uF electrolytic cap connected to what is effectively the output of the OB2.
Isn't that capacitance going to cause problems with oscilations of the OB2?
or have I misunderstood what I have read about capacitors AFTER a gas regulator bottle?.

So off topic, but we had almost 500 mm of rain in 24 hours, so I still haven't painted the chassis. All up we have had almost half a metre of rain in 4 days.

Cheers

Joe