jcalvarez,
You are fortunate to have built your first vacuum tube amplifier over 40 years ago.
In my example in Post # 17, when connecting tap 4 of the bias transformer to ground . . .
The B+ is +300V, and the bias is -50V (both referenced to ground, pin 4).
But since the ground (both power supply returns) are on tap 4, you do not get 350V B+ to ground.
Have it one way or the other, but not both.
I just wanted newbies to know that.
You are fortunate to have built your first vacuum tube amplifier over 40 years ago.
In my example in Post # 17, when connecting tap 4 of the bias transformer to ground . . .
The B+ is +300V, and the bias is -50V (both referenced to ground, pin 4).
But since the ground (both power supply returns) are on tap 4, you do not get 350V B+ to ground.
Have it one way or the other, but not both.
I just wanted newbies to know that.
Just put the auxiliary supply in series with the positive side, not the ground/center tap. Then the bias tap works as expected.
It works. Here are the results.
I understand that putting the additional supply on top would also works. However I think this arrangement has the following advantages:
1) No requirements for high voltage insulation of the booster transformer.
2) The B- can be used not only for bias, but for CCD B- too. You can take much more current than from the usual PT bias tap.
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But they are not both on tap 4, and that is exactly why it does work ...
It becomes clearer when we put a cap to each of the rectifiers.
Now it is obvious that the positive outputs of each of the PSs add together.
And maybe that is the way I would have probably done it.
Anyway, it also works w/o the additional caps.
At first glance I thought the output would see some 50 Hz ripple from the booster rectifier, but that isn't the case, confirmed by sim as well as the boost.
