I have a PZM-6S that had a three-pin XLR on it (looks like it was cut off). Is it possible to get the pin assignments?
Infinity Broadcasting, Fresno
Reply: The PZM-6S is an old model that has been discontinued. Pin 1 is ground, pin 2 is audio (high impedance unbalanced) and –18V, and pin 3 is +18V. Those pins get their power from a Crown PX-T, PA-18 or PX-18 interface (also discontinued).
The PX-T was a Crown device that adapted phantom power to older PZMs like the PZM-30GP, PZM-31S and PZM-6S microphones. The XLR outputs of those mics were unbalanced, high-Z, and were powered by a bipolar DC voltage. You connected each mic to a PXT using regular 2-conductor shielded mic cable. At the output of the PXT, the signal was low-Z balanced. You plugged it into a phantom power supply. The PXT converted phantom power to a bipolar DC voltage that powered each mic.
A PX-18 was the same but worked off two internal 9V batteries and had a 1:1 internal transformer to balance the signal. A PA-18 was the same but worked off two internal 9V batteries and had an active circuit to balance the signal.
The old-style PZMs can be powered by unipolar power as well as bipolar, but unipolar powering reduces their maximum SPL from 148 dB to 120 dB.
Newer Crown mics, like the PZM-30D and PZM-6D, have the balancing electronics built into the mic cantilever or its connector. You simply plug the mic directly into a mic input with phantom power. The output of those mics is low-Z balanced.
The figure below shows how to power an old-style PZM from a 9V battery. If this doesn't work, reverse the connections to the mic's XLR pins 2 and 3.