Even if the amp output is balanced, the mic cable usually has a polarity, so the output may still be asymmetrical. Also if the cable is for a long mic (or for an instrument), and if it has a hot plug, the voltage may still be high enough to damage the mic.
A couple of things to note about the potential for charging the cable. When a mic cable plugs into a microphone input, there is an instantaneous spike of current that may damage the mic as noted above. The solution is to add a resistor of the proper resistance to the mic input to shunt this charge around the microphone. The resistor has to be chosen according to the impedance of the cable. This must be a very low value resistor for a short cable. For longer cables, the resistor is typically chosen so as to counter an anticipated charge of 3.3 V.
When a mic cable is plugged into a battery input to the amp without a resistor, there is a large instantaneous charge on the cable causing a large spike of current. AC supplied amps of the proper design should show this current as a spike going to ground, or shorts occurring in the power supply circuits. The current flowing through the cable is mostly the 1 N solution. The resistance in the cable wire should be chosen with this in mind.
A microphone which supplies phantom power may be connected to an amplifier which provides phantom power for the microphone through a mixer or FX console or channel strip. Although the phantom power is not usable by the microphone, the connection will be likely to cause damage to the amplifier. As a protection, the connection will be blocked, either mechanically or electrically, by a phantom-powered receiver device. Phantom power can cause damage to devices which are not designed to accept phantom power, by applying an excessive voltage to pin 1 of the microphone connector, for example, the power supply of a device which has an active output. d2c66b5586