ba3888s ROHM Co. Ltd., ba3888s Datasheet - Page 5

• Manufacturer Part Number: ba3888s
• Description: High-definition Sound Processor
• Manufacturer: ROHM Co. Ltd.

The input signal is separated into three regions : bass
(20Hz to 150Hz), middle (150Hz to 2.4kHz) and treble
(2.4kHz to 20kHz). These regions are then joined again
with the middle and treble regions phase shifted -180_
and -360_ respectively with respect to the bass signal.
This phase shift adjusts the delay time characteristic for
each band and minimizes the distortion of the rising sec-
tion of the audio signal.
Amplitude compensation (harmonic compensation)
To maintain appropriate auditory balance for the treble
region that is made up of harmonic components, a high-
speed detector and high-performance VCA circuit are
used for amplitude control of the treble component. The
amount of compensation is determined from a calcula-
tion performed based on the DC level input to the CTL
pin, and the DC level detected from the input signal. The
internal control signal obtained from this calculation com-
pensates the amplitude of the treble component input to
the VCA. This amplitude compensation recovers the har-
monic component, and improves the reproduction clarity
(definition level) of instruments and vocals.
Bass boost
To maintain good balance with the dynamically changing
treble component, it is possible to boost the bass compo-
nent. The amount of bass boost can be set in the range
0dB to 9dB by connecting a resistor between pins 16 and
17. When pins 16 and 17 are not connected, the bass
boost is 0dB, (Typ.), and when they are shorted, the bass
boost is at its maximum value of 9dB.
Audio ICs
Noise gate
A high-cut filter is provided to continuously vary the
amount of attenuation depending on the input level, and
reduce the hiss from tape media that is audible at low vol-
ume or on blank sections of tape. This means, that at nor-
mal levels, the attenuation of the high-cut filter is minimal,
and almost no audio information is lost. As the level be-
comes smaller, the attenuation of the high-cut filter grad-
ually increases to cut hiss in a natural sounding way.
Mode switch
The DC voltage on the CTL pin can be used to switch the
IC between processing mode and bypass mode. When
processing mode is selected, the audio signal is en-
hanced using the compensation circuits described above
before being output. When bypass mode is selected, the
signal bypasses all of the compensation circuits, and
only passes through a buffer amplifier before output.
BA3888S
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