Will phantom power damage dynamic or ribbon mics?
When you switch on phantom power in some mixers, phantom is applied to all the mic inputs at once. What will happen if you plug a dynamic or ribbon mic into one of those inputs? Will it be damaged by the phantom powering?
Not if the mic has a balanced output, and is wired correctly. Even if the mic is a dynamic or ribbon type, phantom will not hurt the mic.
Phantom powering applies a positive voltage to pins 2 and 3 in the mic, and the ground of the phantom supply is connected to pin 1. In a condenser mic, pins 2 and 3 are wired to the circuitry inside the mic. Phantom current entering pins 2 and 3 goes through the mic circuit, then exits out pin 1 and returns to the supply ground.
In a dynamic mic or ribbon mic, pins 2 and 3 are wired to the mic’s voice coil or ribbon. Normally, the coil or ribbon is floating from the pin 1 ground. So the circuit loop to and from the phantom supply is incomplete. No current can flow through the mic’s voice coil or ribbon if you apply phantom power. Result: no damage.
On the other hand, if one end of the voice coil or ribbon is accidentally shorted to ground inside the mic, several milliamps of current from the phantom supply will flow through the voice coil or ribbon back to the ground of the supply. This current can deform the ribbon or immobilize the mic diaphragm.
In short, if the mic has a balanced output in which the voice coil or ribbon is NOT connected to mic ground, phantom will not damage the mic. If the mic has an unbalanced output because the voice coil or ribbon IS shorted to mic ground, phantom could damage the mic.
Hope this helps...
Bruce Bartlett
Mic engineer
[Edited by Bruce Bartlett on 08-11-2000 at 12:37]