Phantom Power Testing

Have you ever faced no output from a known-good microphone? Yes? Then you probably are aware that a frequent cause is that the microphone phantom power supply was either turned off or was defective. The Minirator MR-PRO measures the individual phantom voltage at the XLR connector pin 2 and pin 3.

The Minirator MR-PRO measures the actual effective phantom power voltage with or without load. For example you connect the MR-PRO directly to the microphone input of the mixing desk. The Minirator display shows the actual phantom power at pin 2 and pin 3 at no load conditions in the sine wave mode. Full load conditions may be simulated with the help of a special "y" test adapter. Thus in a second measurement, the loaded phantom voltage stability is measured according to the corresponding standard IEC1938. We have summarized technical background information on phantom power and detailed test instructions in the application note “Phantom Power Testing with the MR-PRO”. Download the application note “Phantom Power Testing with the MR-PRO” here.

		Cable test for pin1 detection Imagine you assemble a standard 3-pin XLR cable, but accidentally solder the cable shield to pin 2 and the hot wire to pin 1 on both sides. This cable is commonly analyzed by all cable testers as “OK”, as all pins are 1:1 connected, but the MR-PRO detects such assembly problems. How can a wrongly connected shield be detected? A good XLR cable is a nearly perfect balanced device. For most audio cables the capacities between pin2 – pin1 and pin3 – pin1 will differ less than 5%. Differences higher than 10% are possible indications of a shielding fault. Differences exceeding 25% confi rm an unbalanced cable, caused by a wrongly assembled shield. Measurement Guideline Connect the cable to the MR-PRO output and leave the second end open (=not connected). Select the MR-PRO measurement function “IMPEDANCE” and adjust test level = 0 dBu and frequency = 10 kHz. Select “RL” in the bottom line, showing the detailed impedance results of pin 2 and pin 3. Any impedance measurement result with a deviation of more than 10% indicates already a possible pin 1 assembly problem.
Test results of a 5m audio cable with pin1 failure