We offer a 115V/230V replacement transformer that fits in most Neumann Gefell made tube microphone power supplies.  Historically, they were only made for the former East Block where all countries were set up for 220V/50Hz, and they lack the voltage selector that were standard in the Neumann Berlin made supplies.

In the last few years those "People owned Neumanns" found their way to the US and they require either a step-up or a new power transformer.  The "Step-up" solution doesn't really cut it for studio use as it mostly creates more noise and other problems.  We offer a direct replacement set of transformers that fit right into those historical units, like the N55/60 and 65, that were used to power CMV and UM type mics.  The installation is just a swap, but it should be done by a qualified technician as the filter caps should be changed at the same time.  If you do not know any good techs we can help you find qualified people.