EQ Station Manual v. 2.01 sw. 220 English - TC Electronic
EQ Station Manual v. 2.01 sw. 220 English - TC Electronic
EQ Station Manual v. 2.01 sw. 220 English - TC Electronic
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GRAPHICAL <strong>EQ</strong> TYPES IN THE <strong>EQ</strong> STATION<br />
Reduce the Q of the BP filter by a factor.<br />
Either of these methods solve the boost/cut symmetry<br />
problem to mathematical perfection:<br />
Figure 4 - Asymmetry between '1 + BP´ and '1 - 0.5 BP'<br />
and symmetry error.<br />
But it's still not symmetrical! If we send the signal through<br />
one of these one-band <strong>EQ</strong>s set to +6dB and then through<br />
another <strong>EQ</strong> set to -6dB, the result will be the dashed<br />
(middle) curve in Figure 4 which deviates from neutral by<br />
nearly 2dB!<br />
In some <strong>EQ</strong> designs the ability to use the same BP filter<br />
both for adding in boost cases and subtracting in cut cases<br />
is considered a benefit, and the asymmetry is not<br />
considered a problem. But we prefer symmetry, so that an<br />
<strong>EQ</strong> with one setting is cancelled out perfectly by another<br />
identical <strong>EQ</strong> with the opposite setting. To make the cut<br />
curve (blue dotted in Figure 4) the exact mirror image of<br />
the boost curve (black solid in Figure 4) we need to do one<br />
of two things:<br />
Figure 6 - Boost/cut symmetry problem solved<br />
Now that we've chosen boost/cut-symmetric <strong>EQ</strong> filters, we<br />
will discuss the remaining properties with only boost filters<br />
as example.<br />
Restructure the circuit in Figure 2 from feed-forward to<br />
feed-back topology (Figure 5).<br />
Figure 5 - Single-band <strong>EQ</strong> in Cut-mode implemented<br />
by BP negative feed-back.<br />
- or<br />
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