Sound Quality Correction Circuit - Yamaha YMF795 Manual

YMF795

■Sound Quality Correction Circuit

Sound quality and Gain can be corrected by using an external circuit connected to EQ1 to 3 pins.
The internal circuit configuration of EQ1 to 3 pin and example of the external circuit are as follows.
Gain and filter characteristic can be controlled by a value of C1, C2, R1, and R2.
Gain = R2 / R1. The recommended values: R1 = 22 kΩ and R2 = 82 kΩ (Gain = 3.7 times).
Filter cutoff frequency of f1 and f2 is:
f1 = 1/ (2π×R1×C1).
f2 = 1/ (2π×R2×C2).
If C1 = 0.022 µF and C2 = 120 pF, the cutoff frequency of f1 = 330 Hz and f2 = 16 kHz.
Gain
Gain1
Gain1 -3dB
Moreover, the circuit enclosed with the dotted line is required when mixing with analog signal from AIN is desired.
The level adjustment for mixing depends on the resistance ratio R2/Rx of Rx and R2.
The value of Rx should be 82 kΩ when mixing of amplitude of one time is required.
C3 Rx
AIN
C1 R1
EQ1
FM
VOL
f1
C2
R2
EQ2
-
+
VREF
f2
-35-
EQ3
Freq