On the contrary, if built exactly per schematics and specification, the only thing to change in order to be able to use all the output tubes listed is the rectifier tube type!andrew Ivimey wrote: ↑Wed Jul 12, 2017 9:36 pmThe biasing resistor on the lm317 will need to change depending on choice of valve ... and there's a quite a range between ecc83 etc, so let's assume that this is just a potential circuit with quite a lot of maths to do depending on the valves used. I think the PSU is quite ugly too but that depends on the secondary windings for the HT. I'd much rather use full wave GZ34 than mess with whatever is being used on the schematic.
Still there you go!
5R4 for EL34 and other 25W anode dissipation tubes, 5U4 for 30W anode dissipation tubes, and GZ34 for 35W anode dissipation tubes.
The power supply will yield almost 40V more with a GZ34 than with most 5R4, because the current is set at the same value for any output tube used.
As usual with my designs, there's more to it than meets the eye. If interested, please read the series of articles on the RH Universal amps.