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Filter for Audio Limiter

for DVD

Published in issue 312, July 2002

Filter for Audio Limiter
In the ‘Audio Limiter (for DVD)’ circuit, the peak values of the audio signals are used to reduce the dynamic range of the sound. A possible disadvantage is that the entire audio spectrum is used to determine the level, so that peak levels in the low or high frequencies may lead to suppression of, for example, voices in the mid frequency range. If we divide the spectrum into three ranges and for each range a separate window comparator defines the signal level then the signals in one range will have a smaller influence on the other two ranges.

Components

Resistors:
R1,R2,R13,R14 = 46kOhm 4
R3,R15 = 45kOhm 3
R4,R16 = 73kOhm 2
R5,R17 = 28kOhm 7
R6,R18 = 499kOhm
R7,R19 = 34kOhm 0
R8,R20 = 13kOhm 3
R9,R21 = 232kOhm
R10,R22 = 8kOhm 25
R11,R23 = 8kOhm 06
R12,R24 = 7kOhm 87
Capacitors:
C1,C13 = 15nF
C2,C14 = 39nF
C3,C15 = 2nF2
C4...C6,C12,C16,C17,C18,C24 = 1nF
C7,C8,C9,C19,C20,C21 = 27nF
C10,C22 = 6nF8
C11,C23 = 18nF
C25-C31 = 100nF
Semiconductors:
IC1,IC2 = TL084
IC3,IC4,IC5 = LM339
Miscellaneous:
K1 = 14-way DIL connector (2 off)
14-way flatcable

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