For mics with Transformers (such as MXL2001), I would not be using my jaSb circuit board but instead the T-84 Kit from Mic Parts. I build and test the kit and then use my k47 “Brass Ring” capsule and mount just like my other upgrades. The T-84 kit is for mics with no external switches (like pad or filter). If you have a Sterling Audio ST55 (or Groove Tubes GT55), we would use the T84-55 Kit which supports the switches on those mics.
I use the standard Mic Parts Transformer which I think has a very nice balance of clarity and transformer mojo.
Please Contact me before purchasing so I can get the parts in stock and arrange for you to ship your mic to me.