How to design pre amp for a condenser studio microphone
First some quick googleing:
[https://en.wikipedia.org/wiki/Phantom_power][1]
the german wikipedia has a nicer diagram:
[https://upload.wikimedia.org/wikipedia/commons/thumb/5/5a/P48a.png/300px-P48a.png][2]
from
[https://de.wikipedia.org/wiki/Phantomspeisung][3]
[http://www.sengpielaudio.com/PhantomspeisungDieSchaltung.pdf][4]
OK its in German: Schirm=shield, Kabel=cable, the other words in the diagram are self explanatory, first example is mixer with no phantom voltage and second is mixer with phantom voltage  support...
And here comes your problem! your PC has no phantom voltage support, so so can't directly connect the mic with 48V DC on the signal wires to the PC. you need some galvanic isolation. Your PC is like a mixer without phantom voltage support.
You can buy things like this: [https://www.amazon.de/Neewer-Leistungversorgung-Kondensor-Ausr%C3%BCstung-Musikaufnahmemittel/dp/B019JWZCOS/ref=sr_1_2?__mk_de_DE=%C3%85M%C3%85%C5%BD%C3%95%C3%91&amp;crid=H68I1CKDM3WY&amp;dchild=1&amp;keywords=phantom+speise+adapter&amp;qid=1598427186&amp;quartzVehicle=705-1359&amp;replacementKeywords=speise+adapter&amp;sprefix=phantom+s%2Caps%2C199&amp;sr=8-2][5]
Guess a self build box with all parts isn't any cheeper.
Warning: some sites state 12-48V and state some microphones will die if the voltage is too high, so read your mic's tech. data first.