PSU tube preamplifier.

[vmanj]

Greetings to all.
In my tube preamp, the anode voltage is made according to the diagram (in the image).
I have a question, which connection option (A or B) for the output capacitor will be correct?

 

[ruffrecords]

B

Edit: The MPSA42 has rather a low gain for this application. Its hFE at 10mA collector current is just 40. So if your load draws 10mA you will nee to provided 10/40 = 0.25mA of base current. This has to flow through the 330K resistor so it will drop 330 * 0.25 = 82.5 volts and your HT voltage will drop by the same amount.

Cheers

Ian

 

[vmanj]

Thanks, I'll clarify a little.
Two 12AX7 tube, current consumption is about 5 mA.

Which option is better to choose for connecting the output capacitor (1 µF) for this application A or B?

 

[ruffrecords]

Thanks, I'll clarify a little.
Two 12AX7 tube, current consumption is about 5 mA.

Which option is better to choose for connecting the output capacitor (1 µF) for this application A or B?

Definitely B.

Cheers

Ian

 

[Brian Roth]

Once again, we have a "capacitance multiplier" design. That poor little MPSA42 will quickly die in the real world.

Bri

 

[drtechno]

Once again, we have a "capacitance multiplier" design. That poor little MPSA42 will quickly die in the real world.

Bri

I think these virtual battery power supplies are hilarious. Considering most of these are created this way because they don't know how to cancel things out or avoid them entirely. I like making springy simple CLC power supplies that sag and spring because it gives mic preamps and processing gear an interesting dynamic expansion effect.
I would do something like a CLC with two 2.2 uf and a 15H coil and run AC heaters correctly.
Oh yea other important thing is running a 6X4 tube because solid state power supplies are not that great with tube gear.

 

[Brian Roth]

Hmmmmm....!

Bri

 

[drtechno]

Hmmmmm....!

Bri

Only if you don't know the circuits that doesn't add it to the signal, or subtracts it or avoids it entirely.
Like finding the B+ offset the heater's zero crossing should be at so its signal is never biased into the tube. For example.

 

[vmanj]

Definitely B.

Cheers

Ian

Thanks, I didn't notice that you already wrote option B in your first answer.

 

[vmanj]

Thanks also to everyone who contributed to this thread.