Recording - May 2010 - 47

LEFT

RIGHT

AUX POST

INSERT INPUTS

DIRECT OUTPUT EQUALIZER PAN

AUX PRE

MAIN FADER LEFT MAIN OUTPUTS RIGHT

MIC

PREAMP

CHANNEL FADER

LINE POST AUX SEND PRE AUX SEND POST (FX) AUX OUTPUTS PRE (MON)

Figure 1: Block diagram of a basic mixer’s components

A VERY BASIC MIXER
BUSSES TO MORE CHANNELS

or in time. Post-fader aux mixes are typically used to feed effect processors like reverbs, so that when you fade down a channel, the effect follows the fade. If you’re using five mics on a drum kit and your sound card has only one stereo input, you’ll need to mix those mics in order to record the drums; however when recording a solo vocal, you can bypass some of the mixer’s circuitry by connecting the sound card’s input directly to the mic preamp, yielding (in theory, and sometimes in practice) a cleaner recording. Your mixer may have an insert jack following the mic preamp. A channel insert is both a line level output and input along the input signal path. The Insert jack contains switch contacts which pass the signal straight through when there’s no plug in the jack. Inserting a plug opens the contacts allowing a signal processor such as a compressor to be placed in line with the input signal. The “send” half of an insert jack can double as a direct output by inserting a plug halfway in (to the first “click”) so it makes contact without opening the switch contacts. Other typical mixer features are a headphone jack with its own volume control, dedicated outputs for monitor speakers, more auxiliary send buses, subgroup buses, and auxiliary returns. You can learn a lot about your mixer, or one you’re contemplating purchasing, by studying its block diagram. We often think of a mixer as a large and expensive centerpiece of a studio, but in the DAW era, mixers don’t always have mixing as their primary function. Today we’re seeing small mixers with only a few mic inputs and a few line inputs, but with Figure 2: Block diagram of a typical channel strip

most of the bells and whistles of a full-blown studio console. When properly interconnected, such a mixer makes a great control center for the studio. Channel strips While we’re on the subject of important functions in the analog world, let’s talk for a moment about the “channel strip in a box”. Channel strips grew out of the realization that many features were lost when full-blown mixers disappeared from the studio (or were replaced by cheaper, simpler models). What we now call a Channel Strip is a one- or two-channel box, incorporating at minimum a mic preamp, and an equalizer section, which could be a simple set of tone controls or a fully-parametric design, There’s frequently a compressor, and there may also a line input and an instrument DI. An A/D converter (see below) may be included or optional. Sometimes you’ll also get extras like a gate or a tube saturation stage. The more pricey “famous maker” channel strips accurately recreate the sound characteristics of a vintage console without the bulk and cost. A hardware channel strip connected ahead of a line input can augment a simple mixer or, for recording a single source, can be connected directly to a sound card, replacing important functions of a mixer channel. Line-level inputs vs. Mic preamps: should you worry? Mixers were initially designed to mix microphones, because that’s what studios had. Line-level mixer inputs came along later to accommodate multitrack recorders, effect returns, production

ANALOG

COMPUTER SOUND CARD

PRE

COMP

A/D

DIGITAL

RECORDING MAY 2010

Recording - May 2010

Table of Contents for the Digital Edition of Recording - May 2010