PP Amplifier output impedance matching

[Amie]

Thanks all for your comments.

So, I've been led to believe that to provide a suitable load for the output valves, anywhere between Ra and 4Ra is required for Impedance matching from the full primary of the output transformer, depending on which author you believe.

The RCA manual agrees with the 4Ra, and a small commercial amplifier design that I stumbled upon using those small triodes has a primary of 25K with the specific secondary load.

I had a transformer and speaker in mind for the job but the combination would only give a 12K primary load, half what's needed for it.

I could go with using two valves with both sections in each in parallel?

Use a lower supply?

Use different valves?

I've just been told that the PL81 is an excellent choice, but I don't have any of them!

I have had some successful experiments with PL36's at lower voltages, with a 0-115 0-115 to 0-6 0-6 transformer, but the project would double as a room heater!

Amie.

PS  ra=anode impedance vs. Ra=anode load, where I've referred to them. 
PPS if I get something repeatable and made with available parts I'll post in the homebrew forum.....