Amcron PZM-30GPB
Not much is documented about the Amcron PZM-30GPB beyond its 1978 debut and a modest run of user reports. It was a pioneering boundary microphone, sold in the US under the Amcron name (Crown internationally) for $239. It used a small electret condenser element in a custom housing made to sit on a flat surface. This is the "pressure zone" approach, and it picked up sound in a natural, uncolored way. The polar pattern was hemispherical, and frequency response was rated 50-15,000 Hz. It needed 12-48V phantom power via a 3-pin XLR connector. The mic measured 4.25" high, 2.25" wide and 1.375" deep, and weighed just over a pound. It came with a stand adaptor, a foam windscreen and a 20-foot cable.
Users praised its sensitivity and natural sound for speech and ambience. They noted it worked well in TV news, churches, classrooms and boardrooms. The electret element can degrade over time, and the original foam windscreen tends to deteriorate. Used units today typically run $100-$150, and collectors of classic boundary microphones look for the model.
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