BA3884 Rohm, BA3884 Datasheet - Page 4

• Manufacturer Part Number: BA3884
• Description: High-definition sound processor
• Manufacturer: Rohm

FCircuit operation
The BA3884F / S high-definition sound processor sys-
tem IC treats the amplifier and speakers as a total audio
system, and performs signal processing at the amplifier
input stage to accurately reproduce the rise sections of
audio signals that determine the characteristics of sound,
and ensure that the replayed audio is as close to the origi-
nal sound and as natural sounding as possible.
Problems relating to playback of sound on audio sys-
tems.
With naturally-generated sound, high-frequency har-
monic components generally occur first, followed by the
fundamental frequency components. This also applies to
the attack section of the sound that characterizes many
musical instruments. It is the amplitude component that
gives form to the frequency component and envelope at
the rising point of sound, and this expresses the charac-
teristics of the sound. Therefore, when replaying audio
on audio playback systems, it is extremely important that
Operating principle
To solve the problems described above, the BA3884F / S
performs the audio signal processing described below.
Phase shift compensation
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
Audio ICs
the rise section of the signal be expressed accurately
with respect to the original sound.
However, there is inevitable mismatching between the
speakers and amplifiers in current audio systems. Solid-
state power amplifiers use negative feedback techniques
and operate off a fixed voltage supply, but as speakers
are a current element, mismatching in the system inevit-
ably occurs. In addition, the speaker impedance charac-
teristics are strongly influenced by the electrical reac-
tance of the voice coil, and the mechanical reactance of
the cone assembly. As a result of this, distortion is gener-
ated in the rising sections of audio signals, causing
phase shift in the reproduced sound. In addition, imped-
ance increases in the treble region which reduces the
speaker amplitude and reduces the harmonic compo-
nent, and as a result there is a tendency to masking of
large mid-frequency signal components that follow, and
this makes it difficult to reproduce the rising sections of
the sound.
each band and minimizes the distortion of the rising sec-
tion of the audio signal.
BA3884F / BA3884S
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