Fostex G24S Owner's Manual page 4

he Dolby ype S Noise Reduction System, employed for the first time in Fostex Model G24SA316S, will
be explained below in brief. Dolby'S, while inheriting the Dolby SR technique, " the ultimate noise
reduction (NR) system" developed for commercial use, is a revolutionary NR system modified to the
greatest degree of excellence for consumer use by rationalizing its circuit.
IN Dolby S, as shown in Figure: " Basic concept of Dolby S", the entire frequency band is divided into low
and high ranges at around 400Hz (the low range is processed from 200Hz and below); and further the
level is divided, from Dolby level to -25dB as high level and below this down to -50dB as low level, and
a maximum of 12dB processing applied to each high and low level groups.One stage of the fixed band
type* 1 processor for the low level group, and two stages each of the fixed and sliding band type* 2 are
provided for the high level group.
Now lets compare this with the conventional Dolby C type. he C type has a sliding band for the high
region in the high and low levels (indicated in box of Figure: " Basic concept of Dolby Sj he reason for
dividing it into two levels is to compress, in one step only for the high level input signal and in two steps
for the low level signal, to maintain optimum processing figures against the signals while attaining noise
reduction. Operating merits of each system can be expected in the S type by combining the fixed band to
this. he real value of Dolby S is clearly revealed here and the importance in sound quality is stressed.
And by also providing one stage of fixed band in the low region, the NR effect is applied to the entire
frequency band. As a result, it can reduce noise in the low region by 10dB. Furthermore, the high region
noise suppression amounts to 24dB acquired by two stages of maximum 12dB each which exceeds
20dB in the C type.
Input Level (dB)
Dolby
Level
High Level
Low Level
f(Hz)
Basic concept of Dolby S
-2-