THAT 4301 Dynamics Processor IC
Page 11
The GAIN control (R18) is used to provide static
gain or attenuation in the signal path. This control
adds up to ±130 mV offset to the output of OA2 (from
may be varied from 1:1 (no compression) to ¥:1.
And, static gain may be added up to ±20 dB. Audio
performance is excellent, with THD running below
0.05% at middle frequencies even with 10 dB of com-
pression, and an input dynamic range of over
115 dB.
R
R
16
16
-V+
to -V-
), which is approximately
R
17
R
17
±20 dB change in gain of the VCA. C5 is used to atten-
uate the noise of OA2, OA1 and the resistors R8
through R16 used in the control path. All these active
and passive components produce noise which is
passed on to the control port of the VCA, causing
modulation of the signal. By itself, the 4301 VCA pro-
duces very little noise modulation, and its perfor-
mance can be significantly degraded by the use of
noisy components in the control voltage path.
Perhaps most important, this example design
only scratches the surface of the large body of appli-
cations circuits which may be constructed with THAT
4301.
wide-dynamic-range, log-responding level detector
with high-quality, exponentially-responding VCA
The
combination
of
an
accurate,
a
produces a versatile and powerful analog engine. The
opamps provided in the 4301 enable the designer to
configure these building blocks with few external
components to construct gates, expanders, de-essers,
noise reduction systems and the like.
Overall Result
The resulting compressor circuit provides
hard-knee compression above threshold with three
essential user-adjustable controls. The threshold of
compression may be varied over a ±30 dB range from
about –46 dBV to +14 dBV. The compression ratio
For further information, samples and pricing,
please contact us at the address below.
THAT Corporation; 45 Sumner Street; Milford, Massachusetts 01757-1656; USA
Tel: +1 (508) 478-9200; Fax: +1 (508) 478-0990; Web: www.thatcorp.com
ETC [ ETC ]
