Yamaha YMF795, Manual

Page: 35 / 45

YMF795
-35-
■ 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 k
Ω
and R2 = 82 k
Ω
(Gain = 3.7 times).
Filter cutoff frequency of f1 and f2 is:
f1 = 1/ (2 π ×R1×C1).
f2 = 1/ (2 π ×R2×C2).
If C1 = 0.022 µ F and C2 = 120 pF, the cutoff frequency of f1 = 330 Hz and f2 = 16 kHz.
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 k
Ω when mixing of amplitude of one time is required.
f1
f2
Gain1
Gain1 -3dB
Gain
Freq
+
VREF
-
EQ2 EQ3
FM
VOL
EQ1
R1
R2
C2
C1
Rx C3
AIN