Recording - January 2013 - 47

request a custom headphone mix, auxiliary mix outputs are the usual source. Most of today’s pro audio gear interfaces at the nominal +4 dBu operating level, though the output level of a computer’s built-in sound card is often lower. Most headphone amplifiers have sufficient gain to accommodate consumer sources, though the drummer may not be happy with his headphone volume when the reference track comes directly from a portable music player. Stereo or mono headphone mix? That seems obvious—stereo, of course, since you have two ears and two earphones—but a mono headphone mix for studio tracking was the standard studio setup for 30+ years. A stereo distribution amplifier will provide everyone with the same mix. However, you may not have enough outputs available to feed everyone in stereo when only independent mixes will keep everyone happy. This is a hardware limitation that you must consider when planning your studio or stage setup. Few small-format analog mixers offer stereo auxiliary buses, though you can cobble up a stereo headphone mix using two (mono) auxiliary sends for left and right ‘phones. By sending a channel to two buses, you can adjust the panning by juggling the left and right bus send levels—possible but not convenient. On the other hand, today’s digital consoles are a different story. Since their internal signal routing and control functions are derived through software, the ability to link a pair of buses for stereo operation is a fairly common feature. As one possible example, with Aux 1 and 2 buses “linked,” for a given channel on one particular digital mixer, the Aux 1 Send control becomes the stereo auxiliary mix level while the Aux 2 Send knob pans the channel signal between Aux Outputs 1 and 2. Count your chickens before you hatch a new headphone system! A mixer with six auxiliary buses, when linked in pairs, will give you only three stereo headphone feeds. A previously adequate mixer may become instantly obsolete when band members show up with their own headphones and want their own mixes. And don’t forget to count outboard signal processors—they usually get their inputs from auxiliary sends. DAWs are usually capable of creating as many stereo or mono mixes as you want, but how many you can use for monitor outputs is limited by the number of independent hardware outputs your interface has. An 8-output interface will allow you to have four independent stereo mixes (of which one might be for the control room), but an interface with only one stereo output means everyone must share one mix. Know, too, how your interface counts its outputs, particularly if you’re still in the shopping phase. The marketing pictures may show separate headphone, control room, and auxiliary line output jacks, perhaps with individual volume controls, but if they’re all fed from the same D/A converter they’ll all carry the same mix. Let’s have a look at some representative types of headphone amplifiers and how they might best be used. This isn’t a review or recommendation, but the models mentioned here are representative of the various configurations you might encounter in a search to meet your needs. The headphone distribution amplifier The Aphex HeadPod 4 (see Figure 2) is a typical headphone distribution amplifier; we reviewed its predecessor, the HeadPod 454, in our December 2009 issue. It splits a single stereo input out to four separate amplifiers, each with its own volume control and headphone jack. There’s a master level control ahead of the split for trimming. In addition to being quite a high-hidelity amplifier, it has flexible input connections, minimizing the need for special cables or adapters. There’s a pair of mono left and right line-level input jacks typically fed from line-level inputs, a single stereo input jack typically fed from the headphone jack on a mixer or sound card, and to top it off, a digital S/PDIF input with an internal A/D converter. You can use only one set of inputs at a time (there’s a switch) and although everyone hears the same mix, everyone can control his own headphone volume. Since acoustic musicians generally are comfortable playing to a well-balanced mix, this type of headphone amplifier would be a good choice if that’s your style of music. Of course when it comes to overdubbing individual players, you can

Some History Headphones are really old. Early radios had no loudspeakers, only terminals to connect headphones. Broadcasters from the 1930s worked with headphones but ‘phones didn’t really take a role in music recording until Les Paul started overdubbing in the late 1940s. They became a necessary evil in studios of the 1970s that were built so dead that you couldn’t hear other players more than a couple of feet away, and now they’re expected as a matter of course to help musicians play better.
RECORDING January 2013

Recording - January 2013

Table of Contents for the Digital Edition of Recording - January 2013