Lectrosonics 21750 Polarity-Reversing XLR Barrel Adapter for Earthworks M30 with HM or UH400a/TMLectrosonics 21750 Polarity Reversing XLR Barrel Adapter for Earthworks M30 with HM or UH400a TM Polarity reversing (pin 2 to 3 , 3 to 2) XLR barrel adapter for Earthworks M30 with HM or UH400a TM. This polarity reversing adapter may be needed to correct for asymmetrical current draw in some P48 powered condenser microphones, including older Neumann 100 Series, Rode NTG3 and others. If your microphone does not power on correctly when used with a UH400