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The actual VCF Circuit is a four-stage low pass filter which makes sharp drop of cutoff frequency response.
T5
25C24r2t(R
-
I
f t 6
s E
x
(\t
G'
AC
AC
vAo
tA4558F{'x
n / 2 ,
from DAC1
ln from VCA
8A4558F-OX
l t / 2 1
r ! l
oi-
O +
( J l
I
I
l , t t
I A G
Out
T 3
2SKL2S
ID
c!
(J
I L
2SKL25
B gis
! ,0",n
RLL
cr0 tJ
I F
c30
t0r
R 6 ?
-+
ct0aF
--{F
J3l
I {
rt
CE
I
I
I
-
>
- N
- - - J
\
feed back
The switch S tums on orotf by. signal PF5 from CPU and controls the resonance effectwhich is given by leeding
the ouput sound s4fnat of \tbF back t6ine iriput.
Whgn signal PF5 lqm CFU is Low, th-b- swifch S turns off causing the VCF ouput fed-back to the input.
lf PFs is High; the swilch furns on sendi.ng the VCF output sound to tne last stage of the filter which minimize
the resonance'effect.
lF
I
R ( 9
I
" L l f
! lct2
)
8U40668F
l l / a l
PFS from CPU
i :{ts 5+E
l i*E H
r m ' m A c v A o
l\
Ao
^c
| \---------- Minimum resonance
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