Cwejman S1 MK2, User Manual

Page: 48 / 52

MULTI MODE FILTER
This filter has musical characteristics that differ from the Low Pass Filter. It has low pass, high pass and
band pass mode and is linear, i.e. has no compression mode. Acoustically it is different and provides a
necessary complement to the Low Pass Filter. Both filters can be connected in parallel or in series
(pre-patched), or cross-connected.
No. of poles for low pass mode: 2-4-6 (12, 24, 36dB/octave)
No. of poles for high pass mode: 2-4-6 (12, 24, 36 dB/octave)
No. of poles for band pass mode: 1-2-3 (6, 12, 18 dB/octave)
44
The frequency sweep of the MMF filter in oscillating mode is shown in the illustration below.
MULTI-MODE FILTER (6 POLE MODE),
SELF-OSCILLATION MODE, MODULATED by LFO/SAW
O
U
TP
U
T
(V
ol
ts
)
5.0
2.5
0.0
-2.5
-5.0
-7.5
100 200 300 400 500 600
Time (milliseconds)
7.5
Low pass mode, 2-, 4-, 6-pole, Q-PEAK=7
Frequency (Hz)
20 64 256 1024 4096 20000
AC
re
sp
on
se
(d
B)
-100
-80
-60
-40
-20
0
20
4 pole
Dual band pass mode, dual Q-PEAK, variable SPACING
Frequency (Hz)
20 64 256 1024 4096 20000
AC
re
sp
on
se
(d
B)
-100
-80
-60
-40
-20
0
20
Dual band pass mode, single Q-PEAK, variable SPACING
Frequency (Hz)
20 64 256 1024 4096 20000
AC
re
sp
on
se
(d
B)
-100
-80
-60
-40
-20
0
20
The diagrams below show the filter frequency response for all three modes:
The output signal of the filter in low pass and band pass mode is shown below: the best way to illustrate
the filtering effect is by using the low pass mode (here with 2-, 4-, and 6 pole).
The filtering in band pass mode (cutoff frequency is equal oscillators frequency, square waveform) is presented
below. Observe the difference in filtering effect with 2, 4 and 6 poles; the square signal has been filtered to an
all most pure sinus signal with 6 pole band pass filter.
Time (seconds)
0 0.001 0.002 0.003
Vo
lta
ge
(V
)
-6
-4
-2
0
2
4
6
Low pass mode, 2 pole, Q-PEAK=0
Time (seconds)
0 0.001 0.002 0.003
Vo
lta
ge
(V
)
-6
-4
-2
0
2
4
6
Low pass mode, 4 pole, Q-PEAK=0
Time (seconds)
0 0.001 0.002 0.003
Vo
lta
ge
(V
)
-6
-4
-2
0
2
4
6
Low pass mode, 6 pole, Q-PEAK=0
Time (seconds)
0 0.001 0.002 0.003
Vo
lta
ge
(V
)
-6
-4
-2
0
2
4
6
Band pass mode, 2 pole, Q-PEAK=4
Time (seconds)
0 0.001 0.002 0.003
Vo
lta
ge
(V
)
-6
-4
-2
0
2
4
6
Band pass mode, 4 pole, Q-PEAK=4
Time (seconds)
0 0.001 0.002 0.003
Vo
lta
ge
(V
)
-6
-4
-2
0
2
4
6
Band pass mode, 6 pole, Q-PEAK=4
6 pole
2 pole
Low pass mode, 2-, 4-, 6-pole, Q-PEAK=7
Frequency (Hz)
20 64 256 1024 4096 20000
AC
re
sp
on
se
(d
B)
-100
-80
-60
-40
-20
0
20
2 pole
4 pole
6 pole
High pass mode, 2-, 4-, 6-pole, Q-PEAK=7
Frequency (Hz)
20 64 256 1024 4096 20000
AC
re
sp
on
se
(d
B)
-100
-80
-60
-40
-20
0
20
6 pole
4 pole
2 pole