ba7725s ROHM Co. Ltd., ba7725s Datasheet - Page 7

• Manufacturer Part Number: ba7725s
• Description: Analog Compander For Karaoke Echo Systems
• Manufacturer: ROHM Co. Ltd.

(2) LINE IN / LINE OUT gain
Line amplifier gain is fixed at +18dB.
After being amplified by the internal microphone amplifier, the audio signal is log-
arithmically compressed by 1 / 2 then input to the tertiary low pass filter, which
comprises an internal BF and attached capacitor and resistor.
(3) Echo level control
The DC voltage supplied to pin 4 (BA7725S) or pin 3 (BA7725FS) determines
when the microphone switch is turned on and off and controls the echo level.
Microphone switch control
Echo level control
Attenuation of the primary echo signals from sound
source can be controlled by changing the DC voltage
impressed on pin 4 (BA7725S) or pin 3 (BA7725FS)
between 2V and 9V.
Multimedia ICs
MIC OFF
MIC ON
Mode
MIC AMP IN
– 100
A
– 50
TT
0
LINE OUT
(dB)
0
ECHO LEVEL CTRL pin voltage : (V)
Line output attenuation vs.
echo level control pin voltage
Threshold voltage
L (1.0V Max.)
H (2.0V Min.)
+
R9
Sound source
+
22
5
+12dB
1
Fig.6
Fig.5
R10
Primary echo
21
2
SW
LINE IN
10
Only line audio is output.
Line input and level-controlled microphone input are mixed and output.
Attenuation of primary echo signals can be controlled
by changing the DC voltage impressed on pin 6
(BA7725S) or pin 5 (BA7725FS) .
– 100
A
– 50
Operation
TT
0
(dB)
0
LOOP GAIN CTRL pin voltage : (V)
Line output attenuation vs.
loop gain control pin voltage
BA7725S / BA7725FS
Sound source
5
Fig.7
Secondary echo
Primary echo
10
V
4
= 9.0V
7