Rens Heijnis custom-built audio equipment - Although the DPA/B&K 4003, 4004 and 4012 have a transformer less output and a 130V power supply, for these microphones are also good improvements possible. The
DPA 4003 XLR Adapter - Gearspace.com
PDF] Relationship Between Distance and Microphone Directivity in a Speaker Booth | Semantic Scholar