budget xformer for 829B pentode mode PP (class AB) ?

[vladn]

Few conclusions -
1. for 829B in AB1 plate dissipation is not a limiting factor, the design is limited by max plate voltage, especially for low bias currents.
2. For higher power design a high input Z transformer is needed.
3. With higher plate voltages class A mode operation output power drops.

I know the results are kind of obvious but these simulations were helpful for me to understand how the output stage works.

 

[Jeb-D.]

Those figures look pretty accurate. I suggested 8k because it is an off the shelf edcor value for the 25W transformers. The power output with 8k would be pretty appropriate for 25W iron. As your tests show, you can always go bigger and/or custom windings, it just may be more expensive.