Production clips: Mixers: Smarter than ever

If you were selecting a sound mixing console 10 years ago, you would have only needed to ask how much space it would occupy, how many input channels were required, and how many auxiliary outputs on each channel would be included on the board to suit the planned application.

While in the past decade there have been enormous improvements in analog audio mixers and related equipment, most of the new trends established in that time have been in the digital realm. This certainly doesn’t mean that analog is dead. Major manufacturers are still producing capable analog boards with a variety of features including a degree of snapshot storage. But with digital video upon us, computerized tools available and productions for multiple recording formats becoming common, it is inevitable that the big new trends will be digital.


On visiting a digital broadcast audio control room, the first big change anyone would notice is in the equipment that has been traditionally placed near the mixer. Most of it is gone. Even the ubiquitous patch panel is disappearing, replaced by digital patching and routing within the mixer or its rack-mounted electronics. The concept of having audio signals processed exclusively by physically separate units and never passing through the mixer has been around for at least thirty years but new digital interfaces have taken this concept to its ultimate end. The latest top-of-the-line (and price) digital mixers use multichannel audio digital interface (MADI) to put the routing power into electronic bits rather than pounds of copper.

MADI is an international standard (AES-10) that allows 56 audio channels on a single coaxial cable or fiber-optic interface. A single pair of coaxial cables can provide 54 bi-directional channels of audio and machine control. When using fiber-optic cable as the medium, runs of up to two kilometers are possible without signal degradation. This has revolutionized the connection of multitrack recorders and the relationship between mixers and station routers.


On the mixer itself, the most visible modern feature is the increasing use flatisplays. These have evolved from the analog VU meters, which are still abundant, to segmented bar graphs, to the all-LED display evident on the latest models. One advantage of the flat-panel displays is that changes can often be made with software upgrades rather than buying and installing new modules. Metering has always been a source of wide variance in individual operator tastes, and in response, the latest top-end digital and analog mixers may be ordered with a choice of metering module types. With the advent of internal signal processing including noise gates on each channel, many input modules now include a gain reduction meter beside each input fader. These are desirable for live sound applications using a large array of microphones. Surround sound capabilities have also made vectorscope displays and panning joysticks popular options.


Another indication that designers have been listening to operators has been the addition of dedicated mix-minus routing. For years, broadcast sound operators have specified VCA fader control as the best way to generate post-fader, mix-minus outputs. The VCA fader option, like many other features, was originally included on mixers for other purposes but was adopted by broadcast sound operators as a handy tool for generating mix-minus feeds. The latest digital and analog mixers include a dedicated mix-minus control section where various signals can be selectively subtracted, overall and independent level control is provided, and talkback can be individually assigned.

Total recall

Snapshot storage and recall has been around for awhile, but the newest advance with storing setups is the scope of parameters that can be stored and the choice of internal or external storage media. With more routing and patching functions being incorporated into mixer electronics, the natural progression in snapshot storage is the ability to also store and recall routing configurations. This is a truly significant step. Every broadcast sound operator has a bag of stories about how their state-of-the-art mixer could store and recall snapshots in a flash, only to have the entire show setup trashed by someone making unannounced changes on an external router or patch panel. In stations where there are several mixers of the same make and model installed in multiple control rooms, the advantage of an external storage medium can save the day when equipment failure requires moving the operation to another control room on short notice. The least expensive answer to this situation has been to slip a Type III PC card into the mixer and download the snapshot to the card. Even with a single control room plant, external snapshot storage can be a relatively cheap hedge against total board or computer failure where the snapshots are wiped out. Combined with all-flat-panel displays, snapshot storage can also store all-important individual channel identification (until the show’s guests decide to switch seats).


One popular and current issue is whether or not to go with a mixer that includes surround sound mixing and monitoring. Just do it. The chances are that any top-end digital mixer that otherwise has the needed features will also have some degree of control and monitoring of 5.1 mixes. The driving force behind the trend to surround sound features on broadcast mixers is the increasing prevalence of multipurpose production. While being mixed for a live broadcast audience, the same show may also be recorded for later use on a DVD, Internet or as a radio feature. The consumer market is also making its demands in this area. Practically every home theater system now offers surround sound as a basic property.

HAL does sound

The basic physical source for these new capabilities is the rapidly increasing integration in digital signal processing. DSP advances have made it possible to include on one chip features that five years ago would have occupied a large slice of the entire mixer frame or several rack units of auxiliary processing equipment.

Along with this has come the true marriage of computers and mixers. Digital workstation features, including time code display and selective machine control, have been incorporated into the center section of many recent mixers. When combined with automation and snapshot storage, these boards can handle live production and then quickly convert to a post-production role.

This has a large potential in remote trucks where there are pre- and post-show packages to assemble. In fact, the primary reason that mixers have maintained their physical form with faders and separate meter sections is simply a matter of the human interface. It can all be done on a computer but few operators would seriously entertain the notion of mixing a live show with a keyboard or mouse. These tools are used to navigate the huge array of setup options and modes.

The major cost advantage of heavy computer/mixer integration is evident when upgrades are needed. Most manufacturers offer a wide range of downloadable software upgrades for the popular computer operating systems. Instead of buying more meters or adding another copper-based patch panel, a simple software upgrade can do it all.

Bennett Liles is a freelance writer and TV production engineer in the Atlanta area.