Buzz Audio req-2.2resonance equaliser - Manual (Page 5)

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The REQ-2.2 is a stereo audio equalizer with four “eq” bands per channel
plus a high pass filter and unique “saturation” module. Front panel controls
allow you to adjust each eq band centre frequency, filter bandwidth (or Q)
and the amount of cut/boost. Each element has it’s own on/off switch
which removes it from the signal path when off.
The high and low bands can be switched from a bell filter to a shelving
filter, and the bandwidth control reverts to a shelf slope control when in
shelf mode. The mid bands can be switched between two frequency
ranges as indicated on the front panel.
There are two versions of the REQ, the standard version and a mastering
version. The differences between the two versions are the high pass filter
turn over frequencies (see graphs at the end of this manual), and the
cut/boost controls. The mastering version utilizes a 23 position stepped
attenuator (+/-8dB range) for the cut/boost control, whilst the standard
version offers a continuously variable +/-16dB range with centre detent.
The REQ uses real chokes and capacitors in a parallel resonant circuit
configuration to generate the eq shapes, and this is why it is called the
Resonance Equaliser. Whilst difficult to implement with adjustable
bandwidth, the sound of these passive resonate circuits is far superior to
that of electronically simulated filters.
Unique to the REQ-2.2 is the saturation module which when engaged, adds
subtle amounts of harmonic distortion to the signal and also alters the low
frequency response (see graphs for detail). The saturation module utilizes a
steel core transformer driven by a “single ended” amplifier to achieve this
effect, and is useful in creating a more “vintage” sound. The effect of the
saturation is dynamic in that the higher the signal level, the greater the
effect will be.