Neumann only issued two major series of supplies for its U47 and U48 mics. Both are called NG ( a few late ones were identified as "NG1" , for single mics, and "NG2" for operation of two U47/48 at a time from the same supply.
The first series, made until ca. 1954 still had sophisticated (and expensive) choke coils in the circuit, which did an even better filtering than the series that came after that. It can be easily identified without even opening up the cover: It;s almost twice as heavy as the later series.
If bio want to search for a 'period-correct' power supply for your U47, please submit the mic's serial number, and I will advise what supply is the 'correct' one.
Bottom line: functionally, both original U47 supplies are equally over-engineered, as far as filtering out AC is concerned, and neither of them has ANY voltage stabilization built in.
