Recording Consoles 77927.5.9 Equalizers
For a variety of reasons, signals arriving at the recording console may require spectral
modifi cation. Sometimes this is due to the effect of inappropriate microphone choice or
of incorrect microphone position. Sometimes it is due to an unfortunate instrumental tone
(perhaps an unpleasant resonance). Most often, the equalizer (or simply EQ) is used in
a creative fashion to enhance or subdue a band (or bands) of frequencies so as to blend
an instrument into the overall mix or boost a particular element so that its contribution is
more incisive.
It is this creative element in the employment of equalization that has created the situation that
exists today, that the quality of the EQ is often a determining factor in a recording engineer’s
choice of one console over another. The engineering challenges of fl exible routing, low
interchannel cross talk, low noise, and good headroom having been solved by most good
manufacturers, the unique quality of each sound desk often resides in the equalizer design.
Unfortunately, this state of affairs introduces a subjective (even individualistic) element
into the subject of equalization, which renders it very diffi cult to cover comprehensively.
Sometimes it seems that every circuit designer, sound engineer, and producer each has his,
or her, idea as to what comprises an acceptable, an average, and an excellent equalizer! A
simple equalizer section—and each control’s effect—is illustrated in Figure 27.12.
27.6 Audio Mixer Circuitry ..........................................................................................
Now that we understand the basic architecture of the mixer, it is time to look at each part
again and understand the function of the electrical circuits in each stage in detail.
The input strip is illustrated in Figure 27.9. Note that below the VU meter, the topmost
control is the channel gain trim. This is usually switchable between two regimes: a
high gain confi guration for microphones and a lower gain line level confi guration. This
control is set with reference to its associated VU meter. Below the channel gain are the
equalization controls; the operation of these controls is described in detail later.
27.6.1 Microphone Preamplifi ers
Despite the voltage amplifi cation provided by a transformer or preamplifi er, the signal
leaving a microphone is still, at most, only a few millivolts. This is much too low a level
to be suitable for combining with the outputs of other microphones inside an audio mixer.