Phantom Power Testing0 pages

A p p l i c at i o n N ot e

Phantom Power Testing
with the MR-PRO
Phantom powering is ubiquitous in professional audio. The
MR-PRO includes special features to continuously monitor
and display DC voltages present at its output. The MR-PRO
may be connected to the microphone input of the mixing
desk and continuously measures the actual effective phantom power with or without load. This application note describes how to test conformity of the phantom power source
in use according to the relevant IEC 1938 standard.

General

Minirator MR-PRO measures phantom
power

Phantom powered devices are commonly used in the audio industry. As no additional conductor for power supply is required both
the signal- and power-path share the same connections, thus only
one cable is required, applicable at e.g. microphones and preamplifiers.
Standard IEC1938, covering specifications of audio and video interconnections, also comprises the definition of phantom power
for balanced audio. These specifications, listed in Table 1, determine power and DC-voltage available to the device based on DCload impedance. The phantom power voltage is listed as e.g. P24
(= phantom 24 Volt).

PhantomPower

P12

P24

P48

no load
voltage Pph0

12V+/-1V

24V+/-4V

48V+/-4V

supplied current up
to Imax

15mA

10mA

10mA

R_phantom

680 || 680

1.2k || 1.2k

6.8k || 6.8k

Table 1, Balanced phantom power supply specifications acc. to IEC1938

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Dec 11, Page 1 / 5