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3-39
OPTIMOD-PC
OPERATION
against the look-ahead limiter, causing audible intermodulation distortion between
the bass and higher frequency program material.
Figure 3-3: Bass Clipper Input/Output Transfer Curves as Bass Clip Shape Control is
Varied from 0.0 (Hard) to 10.0 (Soft)
Some OPTIMOD-PC users feel that the bass clipper unnecessarily reduces bass punch
at its factory settings. To accommodate these users, the threshold of the bass clipper
is user-adjustable. The range (with reference to the look-ahead limiter threshold) is
0 to –6dB. (You can also turn the bass clipper off.) As you raise the threshold of the
clipper, you will get more bass but also more distortion and pumping. Be careful
when setting this control; do not adjust it casually. Listen to program material with
heavy bass combined with spectrally sparse midrange material (like a singer) and
listen for IM distortion induced by the bass' pushing the midrange into the look-
ahead limiter. Although the low-IM technology in OPTIMOD-PC's look-ahead limiter
substantially reduces this distortion, overdriving the limiter hard enough can still
cause problems.
In the Five-Band structure, the sum of band 1 and 2 drives the clipper. In the Two-
Band structure, the Bass band drives the clipper.
Bass Clip Shape allows you to change the knee of the input/output gain curve of
the bass clipper. It allows you to control the shape of the "knee"—the transition
between no clipping and flat topping. "0" provides the hardest knee, where the
transition between linear operation and flat topping occurs abruptly as the clipper's
input level is changed. "10" is the softest knee, where the transition starts 6 dB be-
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