DC powers portable or field mixers, through a wall wart or by battery. There's a trade off between capability and size, so carefully assess the features you need most for remote operation. At its simplest, a field mixer can be little more than a four XLR input device with relative volume controlled by knobs. The output can be dual XLR or mini stereo jack to route into prosumer cameras that don't have an XLR input. I suggest adding at least one stereo line input to this basic configuration. If you shoot an event like a wedding, you can use the mixer to take line in from the DJ's board. If weight and size aren't your prime concern, you can opt for three-band equalization as well. Pay particular attention to the quality of construction in a portable mixer,, since mixers used on the road will inevitably be knocked around in transport.

Paul M. J. Suchecki writes for Network TV and shoots and produces documentaries.

To mix effectively, you need good headphones. Field environments change including the speakers you might have available. Even in your own edit suite your monitor speakers can be inconsistent due to changing ambient noise. Don't rely on ear bud / iPod style headphones or noise canceling headphones. Choose an isolation headset (covers the whole ear) that is comfortable with the flattest frequency response that you can find.

Feed a reference tone into the mixer, through the mixer output to your record deck or camera for field work. You always want to monitor down stream because that is the audio you will be recording. Find a comfortable volume level by adjusting the recorder's audio monitor control and then don't change it. You then only use the mixer's faders to make any volume changes. If problems develop, you can work back plugging headphones into different points up the signal chain to isolate the problem.

Cabling Tips
You can eliminate one of the most common audio problems quite simply. We've all heard that annoying buzz from fluorescent lights at 60Hz at the bottom frequency of a human's voice. Microphone cables are shielded, but they can still pick up electromagnetic interference from power cables which carry far more current. Instead of being a neat freak, running your audio cable next to an extension cord, cross it at a right angle. The magnetic fields interfere with each other and the buzz you hear from your microphone should disappear.

XLR cables are fragile, expensive and tend to have a memory. To preserve their usefulness, don't wrap them the way you'd coil a life preserver line in a constant one way loop. Instead use an over/under wrap, reversing each loop. If laid flat, it would make a figure eight pattern. Cables wrapped this way will also pull out without knots.

Finally, try to keep your cable runs short. Signals fall off with cable length. Line level devices can tolerate a longer distance, but microphone cables should be as short as possible. If you find yourself plugging several XLRs together, it is time to switch to a wireless mic.