Fitting a Square Peg into a Round Hole

If you want to use a high-end microphone with your camcorder, you'll have to find a way to convert from the XLR cable to the 3.5mm connector on your camera. Let's explore two alternative ways to achieve this.

The first is a "line-matching transformer" from Radio Shack specifically the A3F XLR Jack-to-¼" Plug Adapter/Transformer (part number 274-016c). Since this product outputs to a ¼" plug, I added a ¼"-to-3.5mm converter (part number 274-875A) to connect to my camcorder. The total cost was less than $20, not including the XLR cable. This rig is shown in Figure 2.4.

Figure 2.4. The Radio Shack line-matching transformer. This right-angle setup looks almost painful.

In my lab, this setup generally works well, though it doesn't supply the phantom power required for many microphones. Ergonomically, however, it's clearly not a field solution, since one inadvertent bump would probably rip my camera into multiple pieces.

If I took the line-matching transformer route in the future, I would choose the Shure A96F transformer, which inputs XLR and outputs 3.5mm, with a flexible cable to avoid the awkward right-angle attachment shown in Figure 2.4. The mail order price for the A96F is around $40.

An even better alternative is the BeachTek DXA-8 "Ultimate Adapter" which lists at $399 but can be found for a few dollars less via mail order. Figure 2.5 shows the two faces of the product, back and front. It screws into the tripod mount beneath your ocrew-camcorder, with a similar mount on the bottom so you can continue to use a tripod.

Figure 2.5. Plug your cables into the front (top) of BeachTek's excellent DXA-8, with controls on the back (shown on bottom here).

On top, as you can see, the unit has three connectors, two for XLR cables and one for an unbalanced 3.5mm connector. The output is a 3.5mm connector with microphone power, so you can plug it into any camcorder with a microphone jack.

With the twin XLR connectors, you can use the DXA-8 to mix together two microphone signals, controlling respective volume with the two volume dials shown on the bottom of Figure 2.5. If you have two microphones, you can capture stereo audio. Even if you capture a monaural signal, as we did in our tests, the DXA-8 outputs the signal to both the left and right audio tracks. This doesn't create true stereo, but it does make sure that you have sound coming out of both speakers.

The 48V switch to the right of both volume controls indicates that the DXA-8, which is powered by a 9-volt battery, can supply phantom power to condenser microphones. In addition, the LMT buttons engage a "limiter" function that prevents distortion from hot inputs this is a critical feature when accepting line-level input from a sound system. The unit also has preamplifiers to boost the low signal from microphones, which can also eliminate hiss.

After trying all these different approaches to converting XLR input, I have to say I like the BeachTek's under-the-camera approach the best. If you don't need all the functionality of the DXA-8, consider the DXA-2, which sells for around $125 and provides one XLR port and one unbalanced 3.5mm input, with volume control but no phantom power or limiters. I would definitely recommend this over the Radio Shack or even Shure A96F approach.