There are a few different circuits for the M 221 B, but here is the main one. For many years Schoeps' schematics and part lists were separate, as in this case.
Schoeps built and wound the transformers themselves for this model, numbered and tested each one (with written test protocols), and selected them for lowest distortion. I don't know of any generally available third-party substitute.
The worst things about the Hungarian forgeries are generally their unselected tubes and carelessly assembled transformers. You might be better off waiting until the real thing comes around. Genuine M 221 Bs aren't all that rare, and (except for the MK 26 three-pattern capsule) the factory still maintains them to a great extent. But they will not accept the counterfeits for repair or upgrade.
Question: What is the model of capsule that you have? In addition to the amplifier scam, were you also sold an MK 240 capsule as a "cardioid"--which it is, of course, but designed for close speech pickup. It has a severe low-frequency rolloff in more general studio applications (e.g. -12 dB at 50 Hz when measured at the usual 1-meter equivalent distance for general-purpose studio microphones) plus a high-frequency emphasis chosen for speech intelligibility, which is not ideal for most music recording. Have you tried exchanging the capsules on the two bodies to see whether the lack of bass "travels with the capsule" when you do so?
--best regards
