I have a U87 build (vintagemicrophonepcbkit.com) that has a fairley low output compared to anothe build I have (Vamisound). Is there any part that contrubutes to lower output or is it just the way they are constructed?
What transformer did you use? Is it wired for 50ohm or 200ohm impedance? What capsule did you use? What values did you use for the C3 cap? Lots of variables here...