Know Your Gear: Anatomy of A Mixer
EQ And PanThe term “EQ” is an abbreviation for “equalization.” The EQ sections of a mixer can be basic or sophisticated, but they all do the same thing - they offer a set of tonal controls that boost (strengthen) or attenuate (weaken) certain frequencies in the sound. A basic mixer might offer two controls of “treble” and “bass.” More flexible mixers may have three controls labeled “hi,” “mid,” and “low.” Very elaborate mixers could have five or more controls for each channel.
On mid-line mixers, the high and low EQ controls are usually “shelving” filters. This type of filter begins taking effect at a particular frequency (such as 80Hz for the low filter or 12,000Hz for the high filter) and continues to alter frequencies below or above the given frequency. The rotary knobs that control EQ can either boost or cut the value by up to 15dB.
Mid EQ is a different type of filter. It’s commonly called a peak filter because it has a peak at some pre-defined mid-range frequency (perhaps 2,500Hz). As this center frequency is boosted or attenuated, other nearby frequencies are also affected. Again, mixers can usually boost or cut this frequency range by up to 15dB.
Next on the input strip is a pan control. The term “pan” comes from panoramic potentiometer. It’s a control that determines the relative strength of the input’s channel in terms of the main left and right outputs. The ear is a wonderful mechanism that is capable of determining a sound’s position within a lateral space. If the sound from an input is sent in equal amounts to both the left and right outputs, then the sound will appear to come from the center of the stereo field. If the pan control is set to full left or full right, then all the sound will come from a single speaker and that will seem to be the location of the sound. As the pan knob is twirled from left to right, the sound will seem to move locations. It’s possible to position a channel’s signal very accurately.
Level ControlsThe fader is used to control a signal’s relative volume in the mix. If your inputs are adjusted correctly, the signal is neither boosted nor cut when the fader is at the value of 0. Even though it is called a fader, these sliders or knobs can be used to boost the signal as well as attenuate it. Most mixers have a boost of up to 10 or 15dB.
The solo button is used to quickly hear that channel’s signal and that signal only. It’s a little like taking all the other channel faders down to their lowest position. It’s possible to solo more than one channel at a time. For example, you can solo the drums even though they might use four channels of the mixer.
When a channel’s mute button in engaged, the entire signal from that channel is removed from the mix. Muting is the same as pulling a fader all the way down, but it’s faster and doesn’t require you to move the fader’s position (which possibly could mess up a perfectly good balance). Like the solo button, it’s possible to mute more than one channel at a time.