I have a microphone with a XLR output and a XLR to PL cable. I don't get from it any signal on my PC. Can I test with a DMM the microphone and the cable in order to locate the problem?
Electronic – test a XLR microphone with a DMM
audiomicrophone
Related Solutions
Originally manufactured as the Cannon X series, by 1950 a locking mechanism was added (Cannon XL)[2] and by 1955[2] a version surrounding the female contacts with a synthetic rubber polychloroprene insulation using the part number prefix XLR. Source: Wikipedia XLR connectors.
The XLR connector is now a standard for balanced microphone connection. In this configuration the microphone capsule is wired to L and R and neither is connected to screen. For an unbalanced microphone one of the mic wires needs to be connected to shield.
simulate this circuit – Schematic created using CircuitLab
Figure 1 and 2 show how to "unbalance" a balanced microphone for an unbalanced input. Figure 3 shows how to connect an unbalanced mic into a balanced input. (Connect one of the L or R pins to shield in the mic plug.)
The circuit assumes a low-Z microphone feeding into a hi-Z amplifier using a transformer for impedance coupling. The transformer is shown for simplicity but can be effected by electronic solutions.
An XLR cable is a "balanced" cable type, which means that it is inherently noise-canceling. For the most-part anyways (nothing is perfect.)
It achieves this by not just sending one signal down the cable, but sending two identical signals - except that one is electrically reversed or opposite from the other. This is called a "differential" mode - when one wire goes positive, the other goes negative. This is beneficial because any extraneous noise that is picked up by the cable is picked up evenly by both wires. This "common-mode" noise is easily rejected.
So long story short, no, a hundred feet of XLR cable probably will make little difference in noise. The signal strength might be reduced slightly due to singal losses, but it should not be noisier because it is long.
That said, XLR cables are great at eliminating the E part of EMI - Electro-Magnetic Interference - or things like radio waves, the "usual" sources of interference. But they are not as good at rejecting the M part - magnetic interference. Luckily, few things produce a magnetic field large enough to be concerned about, so unless you have this cord wrapped around a vacuum cleaner, it shouldn't be a problem.
Best Answer
it's a moving coil dynamic. microphone so a resistance mesurement between the signal pins (pins 2 and 3) should show a few hundered ohms. the microphone may emit a clicking sound during the measurement this is normal.
measurement from pin 1 should show no connection to the other pins.
the cable on the on the other hand should be taking a few miliamperes from the microphone socket, (you'll need to make up a an adaptor so you can measure the current going into the microphone cable also measure the voltage on the plug it shopuld be about 1 to 4 volts.
the other test is to put a signal on the XLR input end of the cable, it only need to be a few millivolts, you could use bare loudspeaker driver and shout into it - you should get some audio outof the cable - so run some software tha graphs what it hears on the microphone socket.
As @PeterBennet prompts me. the microphone cable could be just a plain cable with no in-built circuitry. if that's the case it's not going to work with a direct connection to the PC.