22-09-2019, 08:23 PM
I've got a query about Post 26, you said 4mA was needed, how did you settle on this figure, what made you think it was 'right'? Sounded best, for instance?
As the two windings are equal, yes I'd agree that the ideal current would be expected to be same as Ia of the output valve.
However, more current means lower value resistor, so although the magnetisation is optimised, you are also shunting away more of the audio in the resistor.
And, efficiency is going to be crummy... The circuit effectively wastes the compensation current. It's drawn from the HT supply but contributes nothing to power output. This is why designers either go push-pull, or design the output transformer so that it can cope with steady DC current without saturating.
Looking forward to next post!
As the two windings are equal, yes I'd agree that the ideal current would be expected to be same as Ia of the output valve.
However, more current means lower value resistor, so although the magnetisation is optimised, you are also shunting away more of the audio in the resistor.
And, efficiency is going to be crummy... The circuit effectively wastes the compensation current. It's drawn from the HT supply but contributes nothing to power output. This is why designers either go push-pull, or design the output transformer so that it can cope with steady DC current without saturating.
Looking forward to next post!
