OPERATION.
Front Panel.
The front panel controls are identified in fig.2.
Input Gain.
The input gain of the equaliser may be varied over a range of +/-20dB, which
combined with the different sensitivity inputs, provides adequate and precise control
of signal level. Generally, enough gain should be applied to make the peak LED glow
on the louder sections of music, without causing the LED to illuminate brightly for an
extended time. This will provide the optimum signal to noise ratio whilst allowing
plenty of headroom for boost in the equaliser.
The front panel auxiliary input sockets may be switched between high level signals
(“LO GAIN”, suitable for active guitars and keyboards) and low level signals (“HI
GAIN”, suitable for microphones, pick ups or passive guitars), and are also controlled
by the input gain control.
Peak LED.
The peak LED indicates the output level from the equaliser stages.
The LED will start to glow at a level of +6dBu referred to the balanced output, and be
fully illuminated at +16dBu, where there is still 10dB of output headroom remaining.
Equalisation.
Before switching the EQ into circuit, it is advisable to set the cut/boost controls to
their centre, or flat, position. The EQ is brought into circuit with the overall “EQ-IN”
push switch, signalled by a green LED.
All four bands of equalisation are equipped with fully variable cut and boost controls
of/-15dB of range, swept frequency and variable Q, making them much more
versatile than equalisers equipped with non-variable frequency or Q settings. (The “Q”
of the filter is a measure of the shape of the frequency response curve, and is closely
related to the bandwidth, or range of frequencies, controlled by the filter). High Q
settings (about 5 at the maximum setting on the 3012) result in sharp, narrow
bandwidths generally used for audio correction or effects. Intermediate settings, say 1
to 3, are generally used to enhance or reduce a broader range of frequencies, typically
to make an instrument or vocal “stand out”, or recede, into the mix. Finally, low Q
