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send whatever mix the player wants to hear to the amplifier and there won’t be any squabbling about “the bass is too loud.”

The Main Mix Plus (“More Me”) headphone amplifier Here’s where things get interesting, and why I thought this article needed to be written. There are a few varieties of the multi-output distribution amplifier and it’s necessary to dig in deep, sort out the differences, and decide what best suits your needs. Unless Go Mix Yourself! – Personal Monitoring Systems you’re lucky to find a block diagram (they’re scarce), the best way What seems like the Holy Grail of headphone systems is one to learn what a particular unit can do is with a hands-on trial. that allows each listener to create his own headphone mix without Generally, signal flow in this type of headphone amplifier starts stepping away from his mic stand. While the concept of sending with a single stereo input which is available at all of the headphone several channels of audio out to individual monitor mixers isn’t jacks. Each output has a volume control, and occasionally tone con- new, digital technology has made these system practical. When trols, but wait! There’s more! And that’s where it can get confusing. talking about this sort of system, Aviom and Hear Back The Behringer HA4700 and HA8000 Technologies are the names that usually (see Figure 3) share the same manual, but come to mind first (because they were first on there are significant differences lurking the scene with practical products), but severbetween input and output. Both share the al other several manufacturers have entered “one input to all outputs” concept. The the game in the past couple of years. HA4700 has a pair of Main Input jacks (left On the surface, this seems like a fabulous and right) plus a single stereo Direct input, concept, and in many cases it is. While it while the HA8000 has two sets of inputs frees you, the engineer, of dealing with with a switch for each headphone channel seemingly endless requests for changes to to select whether the listener hears Main Mix the headphone mix, the musicians need to 1 or 2. In addition, the HA8000 has one understand the basic concepts of mixing so Direct input jack for each headphone chanthey don’t just dig themselves into a hole, nel which, when connected, replaces (not ending up with a less than satisfactory mix. adds to) the selected Main input. There are two major components to such a The HA4700 has an Auxiliary stereo system: An interface, or base station, to input for each channel and a single global which the audio sources for the headphone Direct input as well. A Mix knob adjusts the mixes are connected, and the remote stations left/right balance of the Main Input when with the mixing controls and headphone there’s nothing connected to the Auxiliary jack. The interface converts the incoming input. With a plug inserted in the Auxiliary audio to a digital format and sends it out to jack, the Mix knob changes function and the remote mix/headphone stations, usually adjusts the Main/Auxiliary balance. The Feeding Stereo Inputs From Auxes over CAT5 Ethernet cable. The system is conIt’s worth noting that most auxiliary figured much like a computer network, with Direct input on the HA4700 replaces the main input for all headphone channels. One and direct outputs, even when bal- an Ethernet hub or switch used to distribute anced, are single ended, and that’s fine audio to a large number of mix stations. potential use is for hearing a playback. Since each headphone channel of the for feeding a stereo input as long as Depending on the architecture of the particuHA8000 can be fed from either the Main you can route the signal to both ears. lar system, the actual mix can either take or Direct input, you can set up a combina- But if you have a real symmetrical out- place in the box at the listener’s position, or tion of global (one-to-several) and custom put (transformer or electronically bal- that box can serve as a control surface, with (one-to-one) headphone mixes. The anced) you don’t want to feed the high the actual mixing taking place in the base staHA4700, on the other hand, can become and low sides of the output to tip and tion at the source end of the cable. a “more me” headphone amplifier by ring of a stereo input. That will put the Typically the base station receives audio adding a channel’s Auxiliary input to the input source 180 degrees out of phase from a mixing console or a DAW equipped Main mix. You’ll need to be creative to in the left and right ears. This sounds with a multichannel computer audio interface. find the “more” sources—direct outputs, very weird and is undesirable. Use just Typical sources are direct outputs from the mic auxiliary outputs, or subgroup buses are one side (tip or Pin 2) of the symmetri- preamps, stereo subgroup mixes (stems), and cal balanced output instead. usually good places to look. dedicated sound sources such as a Other popular “more me” headphone metronome, drum machine, or prerecorded amplifiers are the ART HeadAmp 6 and its cousin, the backing tracks on a CD. Isolated headphone mixes, particularly HeadAmp 6 Pro. These are similar to but not functionally iden- with in-ear phones, can be pretty dry, so some of these systems tical to the Behringer amplifiers. Both ARTs have a master Direct include a reverb processor. Lacking that feature, you might include input jack which overrides the signal from the Main inputs. Like an ambient mic for the musicians’ mix, or provide an overall reverb. the HA4700, both ARTs have an Auxiliary input and Mix knob Because the controls at the mix station are operated by musifor each channel, but Behringer and ART manage mono/stereo cians who aren’t necessarily engineers or computer technicians, differently. Behringer has a Stereo/2CH switch for the Auxiliary the user interface is usually quite straightforward. Each input input. This allows a mono “more me” source to be centered in source has a volume and pan control though some go beyond the phones. that and offer eq either on the overall mix or on individual chanART’s approach to this is to provide left, right, and stereo nels. The Movek myMix (Figure 4), perhaps the most fully feaswitches for each headphone output, which puts the entire head- tured (and, in my opinion, the geekiest) of all of the multichanphone mix (main + auxiliary) in mono. If you want a stereo nel personal monitor systems, puts all of the controls in a tiny headphone mix with the Auxiliary input centered, you’ll need to box with a big knob, a touch screen, a few buttons and the tie tip and ring together at the plug going into the Auxiliary Input headphone jack. jack. But in trade, you can feed one mono mix to the left input, This sort of headphone monitoring system is an elegant solution a different mono mix to the right input, and the listener can put for the self-contained performing band that uses the same setup for his phones in mono and select between the two mixes. each performance and wants to switch to in-ear monitors. But in
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Another popular “more me” headphone amplifier, the PreSonus HP60, has a mono button that works on the Auxiliary (they call it “External”) input so it’s simple to feed this input from a mono output like a mixer’s Auxiliary send or direct output. See the subtle nature of the differences? But they’re important as no two are exactly alike. Choose your weapon.

Recording - January 2013

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