Digital mixing console

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In professional audio, a Digital Mixing Console (DMC) is an electronic device used to combine, route, and change the dynamics, equalization, and other properties of digital audio samples. The digital audio samples are summed typically to what is known as a master channel to produce a combined output. A professional digital mixing console is a dedicated desk or control surface produced exclusively for the task. A computer with proper controller hardware can act as a digital mixing console since it can mimic its interface, input, and output, but a dedicated hardware mixer is typically more robust in terms of user control, processing power, and quality of audio effects.

Yamaha M7CL in place for a live production

Uses

Digital mixing consoles are typically used in recording studios, public address systems, sound reinforcement systems, broadcasting, television, and film post-production.

Common sound system problems and solutions

Most DMCs are expensive and sophisticated tools. The most common problem associated with their use is lack of skill on behalf of the user. They require deep understanding of signal flow, audio terminology, and hardware implementation.

Another pitfall in terms of live applications are improper location of the equipment. The sound operator is often secluded in an enclosed room behind glass, etc. No sound operator can properly adjust a live sound system unless he or she can hear exactly what the majority of the audience hears.

Part of the solution to alleviate operator issues is to automate whenever possible. The advent of modern digital computer technology has now made it possible to install sound system components that will almost operate themselves. When upgrading or installing new sound systems, it is advantageous to install items that require as little hands-on, human operation as possible.

Some digital mixers have controls that mimic the classic look and feel of analog mixers. This is comparable to a fly-by-wire system in modern aircraft. The controls are similar, but the underlying mechanism has changed from voltage levels to binary information.

A digital mixing console can offset the lack of operator experience because it can store the settings programmed by an expert mixer. For example: A knowledgeable person can adjust all of the microphone settings, monitors, etc. for a given event. After everything is properly adjusted, that set-up is assigned a name and stored in the memory. Afterwards, a less knowledgeable operator can simply select that setting on their console or computer.

One can easily program many different preset configurations or "snapshots," into the mixing console. Default configurations that are included with the DMC are known as presents. Once a stored setting is recalled, the operator can still make manual volume adjustments, etc., without affecting the stored program. In other words, they can change a lot of stuff and all one has to do is hit the recall and the mixer automatically returns to all of the correct start-up settings.

Digidesign's Venue Profile mixer on location at a corporate event. This mixer allows plugins from third-party vendors. A Smaart software screen is partially shown on the right—Smaart allows plugins, too.

Another advantage of DMCs is the abundance of control features that it provides for each input channel. The built-in effects of typical DMCs are robust and include gates, compressor limiters, equalizers, feedback controllers, and other signal processing hardware. One advantage of the large number of internal effects is that a DMC system is less vulnerable to failure and outside interference than a set-up using outboard hardware.

Third-party plugins can add functionality in a digital mixer. Plugins allow for further expansion of the mixer's on-board equalization, compression and reverberation effects.

When mixing for recording purposes, one can rely on headphones alone. The opposite is the case for live sound mixing. No sound operator can properly adjust a live sound system unless he can hear exactly what the majority of the audience hears. For issues related to space, appearance and security, one cannot always locate their sound control equipment, out in the middle of their auditorium. This is even more of a problem if the auditorium is a multiple use building that is often converted for other events.

A digital mixer can also solve this problem. A sound operator can operate the whole sound system from a laptop or desktop computer. With the proper set-up, it can even be done by a wireless laptop configuration for increased mobility. In fact, many of the digital mixer's functions are easier to operate from the computer screen than the actual mixing console.

Using dual DMCs to improve live recording

In truly professional broadcast and recording applications, one does not use what is referred to as the house mix for high quality audio recordings. There is a simple reason for this. When one is engineering live sound for any auditorium, one must deal with the acoustic parameters of that particular auditorium. This requires various adjustments of equalization, bass, treble, volume, etc. While those adjustments may enhance the sound quality in the auditorium, they are not necessarily needed for the recording. In fact, those house mix adjustments often diminish the quality of the recorded sound. Once the bass, treble, volume and other effects of the house mix are added to the recording mix, it is most difficult to correct. In the reverse, adjustments and signal processing effects that are often used to enhance a recording mix are not always needed in the house mix.

In order to facilitate this, the signals must be split and provided to OB, recording crew or film crews. This split can be analogue or increasing digital, an analogue split will normally be a feed of all stage signals split either passively or through an isolated transformer split. Transformers are preferred as they provide isolation and prevent microphone pre amp on different systems interacting, for example a recording preamp causing level change at FOH or Monitors.

A digital split can come in many forms, Often AES/EBU, MADI, Firewire direct to DAW, or increasingly network aware digital snake formats, such as AVB, Dante, Ethersound or Rocknet, many other proprietary formats also exist.

Advantages and disadvantages

Advantages

There is no added noise, (unintentional) distortion, or other signal degradation while the signal is in the digital domain, between the output of the analog to digital converter (ADC) and the input to the digital to analog converter (DAC).
Aux sends can be mixed on the main faders rather than on a row of potentiometers.
Signal routing is often much more flexible than with an analog-based console.
The setup of the console can be saved and loaded at will. This is particularly useful in live events where a setup for each band can be largely prepared in advance, saved, and then loaded as needed.
There are typically many on-board effects and virtual signal processors available, eliminating the need for additional hardware modules, and the associated cost, size, weight, cabling, signal quality issues, etc.

Disadvantages

There is an analog to digital conversion, then processing of the signal, then again digital to analog conversion, which degrades the sound quality. This is subject to debate, since the quality degradation is not always noticeable.
The number of faders is often less than the number of input channels. The extra input channels are not accessible until a bank of faders is switched to control them.
Digital conversion and processing adds latency, or delay, into the signal.
The act of making adjustments is often slower for compact digital mixers which require the user to page through one or more layers of commands before reaching the desired control.