The headphone-cue function (also called cue or pre cue) found on all good DJ mixers is an amazing invention. Originally, its sole purpose was to allow a DJ to cue up one song in his or her headphones, independent of another song playing through the mixer's main stereo outputs. But as DJs have moved beyond simply segueing between two songs to mixing multiple beat-matched sources, their need for greater cue functionality has inspired significant advances in headphone-cue systems. For example, the best cue setups now have an independent headphone mix that can combine multiple channels and the main stereo output, with the ability to “split” these sources between either or both of the headphone's earpieces (such as cue source left and main mix right).
Not surprisingly, a DJ mixer with a well-designed headphone-cue system can be a powerful ally for live electronic-music performance, especially if your focus is mixing audio loops and MIDI sequences on the fly. For example, you may need to beat-match and tune several loops privately, in your headphones, before introducing them publicly, in your live groove. To take full advantage of a DJ mixer's cue system, it's important to think about how you're connecting your gear to the DJ mixer and understand clearly where all of the signals are being routed.
NOT YOUR PARENTS' CUE
The headphone-cue system of a DJ mixer is designed differently than a traditional recording console's headphone-cue system. Therefore, even if you're a studio whiz, you may not be familiar with a DJ mixer's cue setup and operation. The main purpose of a studio mixer's cue system is to provide a headphone mix for session musicians. A custom headphone mix — in which, for reference, some tracks are mixed louder than others — can help inspire a musician's performance. Professional consoles let you adjust the level of each channel sent to the headphone mix, independent of each channel's level in the control-room mix (what the engineer and producer are hearing).
By contrast, the cue system of a DJ mixer is optimized for setting a channel's program (such as a song or a loop) level to match the program level at the main output (the house mix). A channel's trim (also called gain) control is employed to adjust the program's prefader output level and the levels in your headphones. This setup makes it possible to adjust program levels in your headphones that will retain their relative volumes when added to the main mix (assuming that the channel faders are at their null position, having no affect on the channel's volume). For example, when segueing between songs, you can crossfade without fear that the next song will be too loud or soft compared with the previous song.
During a live performance that incorporates multiple sources, such as loops and sequences, the ability to set the mix levels of several sources at the same time is crucial. For example, you might cue two or three loops simultaneously, mixing them together in your headphones, before introducing them one at a time into the main mix. With each loop's prefader level set, there are a variety of ways to add the loops to the mix: fade in a loop with the channel fader (stopping at the null position, which varies between mixer models), drop in a loop using the channel's phono/line switch (line position brings the loop in whereas phono cuts the loop off) or use the crossfader to crossfade between loops (in this case, make sure the crossfader is not controlling your main program channel — the channel with the groove or song over which you're playing).
TAKING FULL ADVANTAGE
To get the full benefit of a DJ mixer's headphone-cue system, you need to have discrete control of each of your sound sources. For example, you can't cue a groove box's bass and drum loops separately if both parts are coming in the same mixer channel as a stereo mix. The solution is to employ a groove box with individual outs, assign the drum and bass loops to separate outputs and then connect each output to its own mixer channel. This setup will allow you to cue each part individually. But do keep in mind that having several groove boxes and many individual outs will require a good-size DJ mixer that can accommodate four or more simultaneous inputs (such as the Vestax PMC-500) — a 2-channel mixer won't cut it for this setup.
You can also employ software programs, such as Propellerhead Reason and Cakewalk Project5, that can address multioutput audio interfaces, such as the MOTU 828mkII. For example, assign different categories of loops (such as drums, chord progressions and bass lines) and sequences to different outputs; then, connect each output to its own mixer channel. A few programs, like Ableton Live and Native Instruments Traktor, feature a dedicated software bus for headphone cueing. With programs such as these, you can use an audio interface that has just two stereo outputs, such as the M-Audio Quattro USB. One stereo output functions as the headphone cue (and is connected to a mixer channel assigned exclusively to your headphones) and the other as the program stereo mix (which is also connected to a mixer channel assigned exclusively to the mixer's main mix out).
Once your system is set up to take full advantage of a DJ mixer's headphone cue and you know how to use the trim control, as well as understand the basics of DJ-mixer signal routing, you will rarely make a mistake involving mismatched levels. But just because you can headphone-cue anything doesn't mean your head should be buried in your computer or mixer during a set — headphone cue is not an excuse for being unfamiliar with your record or loop collection.