Help me Pick an Adapter

February 1, 2003

Q. At Videomaker’s advice, I got myself a balanced microphone and balanced cable to reduce interference from electromagnetic noise. I know I need an adaptor to get the signal from the XLR cable to the mini-plug my camcorder needs. Now I understand that these adaptors come in several varieties, and that getting the wrong one can cause phasing problems. Could you tell me exactly what I need?

Peter Reingold

Internet

A. It seems like this should be less complicated, but unfortunately, it is not. You will place your adaptor, not between the microphone and the XLR cable, but at the other end of the XLR cable . One end will plug into the XLR cable, the other into the camcorder. In addition to changing the type of connector leading to the cam, this adaptor will unbalance the balanced signal coming to it from the XLR cable. This is good only because your cam is made to accept only an unbalanced signal. It will still receive the noise-reducing benefits of your balanced microphone and XLR cable for the entire length of the cable. Only the short cable in the adaptor itself is unbalance and more vulnerable to radio-frequency noise, so buy an adaptor containing as short an unbalanced cable as is possible for your uses. The good news is that for most cams, the price for this adaptor will run toward the lower end of the $20-$55 price range.

Before shopping, find out whether the microphone jack on your camcorder is stereo or monaural. You will find this information on the spec sheet in your owner’s manual. This step is very important. Much unhappiness has resulted from plugging stereo plugs into mono jacks and vice versa.

Second, determine whether your balanced microphone is monaural or stereo. If the microphone is mono and the adaptor is built to receive XLR stereo (or vice versa), it will create a phasing problem that can ruin your audio or even make your audio disappear (see explanation in the October 2002 Tech Support).

Finally, look at the XLR jack at the end of the cable you need to plug into the camcorder . Typically, this will be a male 3-pin XLR connector.

If your microphone is mono and your cam has a stereo jack, you need a female mono XLR to male stereo mini (1/8") adaptor . This will send the mono signal equally to both of your cam’s channels. Note in the photo that the mini plug has two black rings near the tip. These show that it is indeed a stereo plug. This is also very important: make sure that the specs for the adaptor say that it has "audio bridged to both channels." Some adaptors in the market wire the microphone’s monaural signal to only one of the camcorder’s two channels. At best, this gives you no sound in one channel. At worst, it creates problems with some editing systems.
If your microphone is mono and your cam has a monaural jack, you will need a female mono XLR to male mono mini (1/8") adaptor . Note in the photo that the mini plug has only one black ring near the tip. This shows that it is a monaural plug.
If your microphone is stereo and your cam has a stereo jack, you need a female stereo XLR to male stereo mini (1/8") adaptor. Beware: this will look exactly like the mono XLR to male stereo mini (1/8") adaptor shown in Figure 3. You must read the specs of the adaptor to find out whether it is of the mono or stereo variety.

If your microphone is stereo and your cam has a monaural jack, you need a female mono XLR to male mono mini (1/8") adaptor. This will mix the two channels from the microphone into your cam’s single channel. This adaptor will look exactly like the one shown in Figure 4. Only by reading its specs will you find out whether the adaptor is meant to receive stereo.

One last caution: Some older DV cams need "DC voltage blocking" built into their adaptors. Some retailers of audio equipment have lists of those models requiring this adaptation.