The supply, filter & gain unit PRE-33A has been designed to match Aco Pacific’s microphone capsule 7012 (and relative preamplifier 4012) and is needed to operate it. The PRE-33A powers the microphone connected to its input with a 200V phantom supply and adds a selectable weighting filter (A or B or C); also available there is a configurable attenuation/gain stage (-20dB/0dB/+20dB). The unit is operated with two standard 9V batteries or with an external DC power supply.