Phantom power
Phantom power referred to in audio engineering, a special type of power supply for condenser microphones with a DC voltage 9-48 V (DIN 61938, vorm. DIN 45596 ). In practice widely used is a supply voltage of 48 V ± 4 V ( phantom power P 48 ).
Phantom power is used for condenser microphones to operate the electronics in your microphone.
Design and operation
Phantom power is dependent on a balanced microphone connection. Here, the positive pole of the supply voltage via two well- paired decoupling resistors (6.8 kOhm at 48 V supply voltage ) to both the signal line a and b to the signal cable is laid, where the decoupling resistors prevent a short circuit of the signal. The negative terminal of the phantom power is fed through the cable shield. Between the wires a and b is thus no voltage (hence the term " phantom power "), but probably. Between each of the two wires a and b and the common shield
Possible interference voltages in the power supply affect the symmetrical routing is not on the modulation (signal voltage ) (see the common mode rejection ). An energizing a plurality of microphones by a single power supply is possible. When connecting an unbalanced source phantom power, the corresponding input in the rule must be switched off.
The following are defined phantom power with different voltages. Usual, the voltages 48 V, 24 V and 12 V. For the different voltages different decoupling resistors are required:
The actual resistance value of the decoupling resistors can vary up to 20% of the specified value. Contrast, very critical is the equality of both decoupling resistors whose values may deviate by a maximum of 0.4 % of each other, as it could otherwise cause interference.
Digital Phantom Power ( DPP)
For digital microphones defines the AES42 standard, the so-called Digital Phantom Power 10 V at a maximum of 250 mA. Such microphones can be remotely controlled by modulating the phantom voltage to 2 V.
Compatibility of the phantom power
Condenser microphones
Most condenser microphones are set to a specific phantom power. Today, the 48 - V power has prevailed, but most microphones can work with values between 12 ( often 9) and 48 V.
Dynamic Microphones
When using dynamic microphones phantom power is not needed, it harmful to the microphone on the other hand does not (if it is connected in a balanced ). In practice, therefore, it does not matter if the phantom power is on or off. This distinguishes the phantom power of the T-power currently used only in special cases according to DIN 45595, in which a DC voltage between the signal lines a and b, that is, parallel to the microphone capsule is present and would damage a dynamic capsule.
Ribbon microphones
There are special ribbon microphones that contain active electronic amplifier instead of a transformer. This uses phantom power for power supply. In particular, older conventional ribbon microphones are destroyed by applying a Tonaderspannung to the wires a and b in the rule, since the ribbon blows. Phantom power is not critical in this respect, since no voltage between the clay veins located.
Current Ribbon microphones tolerated in general, the application of a phantom power.
DI boxes
Active DI boxes also need phantom power, provided they are not operated from batteries. In order to avoid that in the absence of power, no signal is output, have some direct boxes through a bypass function, wherein the signal bypasses the electronics.
Optogate
Opto Gates need to power also the usual 48 V phantom power.