BA3884 データシートの表示（PDF） - ROHM Semiconductor

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BA3884

High-definition sound processor

ROHM Semiconductor 

Audio ICs

BA3884F / BA3884S

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 CTL1

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 is determined by the DC

level applied to CTL2.

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.

External components

The frequency characteristic in processing mode with

maximum definition level and maximum bass boost is

given below.

C1 : External capacitor connected

between the VCA and MIX pins

(0.068µF in the application

circuit).

C2 : External capacitor connected

between the OUT and MIX pins

(470pF in the application

circuit).

As indicated in the diagram, capacitors C1 and C2 deter-

mine the treble component cutoff frequency. By varying

the values of these components, the frequency charac-

teristic can be changed as indicated by the dotted line in

the diagram. This varies the balance of the harmonic

component, and is an important factor in determining the

tone quality.

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