It is a frequent occurrence that condenser microphones are bought from a music store and returned the same day by people who are convinced their microphone did not work to begin with. It is logical that one should test what one intends to buy before leaving a store, but, of course, salesman should always prompt this to begin with. 

After reading the clear instructions on the microphones box and with the push of a button on a mixer/soundcard the mic springs to life much to the client’s delight and the salesman’s relief. What was missing was merely a clear understanding of ‘Phantom Power’.

So let’s begin.  Basically put, Phantom Power is DC voltage (up to 52 volts) supplied through pin two and three of a mixer’s ‘XLR’ input socket that powers a condenser microphone when it is connected. Pin one is the ground for both audio and power. If a condenser microphone does not receive power, it will not work. The reason for this is simple – a condenser microphone’s diaphragm needs an electric current for it to operate.  Microphones that do not require power simply ignore the DC present between pin two/pin three and pin one. Dynamic microphones, as well as the balanced mixer inputs, ignore this voltage. Different condensers require different voltages, so one should check the specs of the microphone.

Generally, speaking, a microphone which only requires 9, 12 or 24 volts will have a regulated built in transformer, so that 48 volts will be reduced to the required voltage and not damage the microphone. Most microphones that require higher voltages often come with their own Phantom Power supply – specifically tube microphones. In this case, it is unnecessary to use the desk’s Phantom Power.