BH3868BFS Rohm Semiconductor, BH3868BFS Datasheet - Page 26

• Manufacturer Part Number: BH3868BFS
• Description: IC AUDIO SOUND PROCESSR SSOP-A32
• Manufacturer: Rohm Semiconductor
• Type: Volume Controlr

Specifications of BH3868BFS

• Applications: Automotive Audio
• Mounting Type: Surface Mount
• Package / Case: 32-SSOP
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

BH3868BFS
Audio ICs
! ! ! ! Problem in Sound Reproduction with Audio System and BBE Process
In general, for the natural sound, treble harmonic element is generated first and then bass basic wave element is
produced. This is the same with the attack part which shows the characteristics of various musical instruments. The
amplitude element, which forms a frequency element and envelope at the rise of sound, expresses the character of the
sound. Therefore, to reproduce any sound with a playback system, it is very important to express accurately the rise of
sound against the original sound. However, there is unavoidable mismatch between a loudspeaker and amplifier of
today’s audio playback system.
For example, a power amplifier with transistor operates as constant-voltage source, but mismatch cannot be avoided
because one loudspeaker is a current element. Moreover, the impedance characteristic of loudspeaker is affected
considerably by electric reactance of voice coil or mechanical reactance of cone assembly. As a result, the rise of sound
is distorted and the phase of playback sound is deviated. Furthermore, due to the increase of treble impedance, the
loudspeaker amplitude is reduced and the harmonic element is deteriorated. So the treble element is easy to be masked
by a consequent middle tone element of high level, and the rise of sound is hard to be produced accurately.
BBE has been developed to solve those problems. BBE is a technology to reproduce the sound clearness more naturally
by moving the delayed harmonic before the basic wave first to construct the same wave as that of the natural sound and
then boosting slightly the treble which is easy to be attenuated. Because of the synergistic effect of phase correction and
treble boost, the same clearness can be obtained by approximately half boost in comparison with a simple boost of
equalizer. It has been ten years or more since BBE was introduced into many recording studios, PA, SR sites and
broadcasting stations, and 100,000 or more units of BBE for professional have been using. BBE is designated by many
musicians to improve the sound of vocal and musical instruments.
! ! ! ! Principle of Operation
To solve the problems in audio playback system mentioned in the previous page, the BBE processor processes a signal
as follows:
! ! ! ! Phase Correction
Bass
Middle
Treble
20
150
2.4k
20k
f (Hz)
By dividing the input signal to three frequency bands, “Bass” (20 to 150 Hz), “Middle” (150Hz to 2.4kHz) and “Treble”
(2.4k to 20kHz), and by adding them again, the phase difference −360° in Treble and −180° in Middle against Base are
generated. These phase differences adjusts the time delay characteristic in every frequency band and minimizes the
distortion of the rise of sound.
! ! ! ! Revision of harmonic element
Gain is applied to Treble, because the harmonic element (Treble element), of which gain is expected to be deteriorated
depending on the loudspeaker characteristic, must be enhanced. However, if Treble is clear, it may seem that Bass is
insufficient. This can be corrected by applying the gain to Bass.
There are many audio system characteristics. The most suitable correction effect for your system can be obtained by
BBE.
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