The N 149 A power supply generates the necessary operating voltages for M 147 Tube, M 149 Tube or M150 Tube microphones. It operates with all mains voltages from 100 V to 240 V, 50 or 60 Hz. Mains power is connected through a standard IEC 320 socket. The microphone connects via an DIN-8 connector.

The microphone signal is fed to a XLR 3 M connector. The modulation output is balanced. The N 149 A supplies the bias voltages for the microphone capsule, the filament voltage controlled by a sensor circuit, and a further voltage to generate the plate voltage and other necessary operating voltages within the microphone itself.

The unit produces constant current effecting a soft start of the tube. The KT 8 cable between microphone and power supply can be up to 100 m long. Modulation cable lengths up to approx. 300 m are allowed.The three available versions of the N 149 A just differ in their enclosed mains power cable.