What I was thinking? - I was right! (Phantom power)

[SirEgno]

some years ago I started to build a mic preamp with phantom power supply.
I bought a 2x15v transformer as main power and for the phantom a... 2x12v transformer.
What strange drugs did I take to get this idea? How can I get 48v from 2x12v transformer?

I bought also every component to build this project and there is no charge pump or something similar.
Only a 48v zener diode.

[davent]

Voltage doubler?


dave

[SirEgno]

you're right!
my knowledge is regressing 
Are there some advantages using a full bridge rectifier?
like this:


Doubling the voltage the current is halved, right? the transformer is 0,5VA (2x0,25). so the current should be about 20mA?

[davent]

If i recall, peak voltage with a doubler is 2.8 times the secondary so i've gone with the ampere rating divided by the 2.8 factor. I've used the simple version in a number of tube amps for the high voltage rail, they've run with without issue for years. No idea whether the bridge may offer in improvements.
dave

[SirEgno]

So, 24*2.8=67.2. That's why I also bought a 48v zener diode.

The schematic attached should be fine. But I think I have to add a resistor on the red circle. right?

Thank you very much for helping me!

[davent]

Your welcome.

The resistor, i don't know but, there is this project for a phantom  48v supply from Rod Elliot that uses a voltage doubler, he has a small value resistor in each power line.



https://sound-au.com/project96.htm
dave