851D
azur
13
ENGLISH
Minimum phase filter
-80
-60
-40
-20
0
20
-200
-180
-160
-140
-120
-100
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Magnitude (dB)
Frequency response
frequency/FS (input sampling rate)
The Minimum Phase filter is another highly regarded audio filter that
offers even lower ripple in the pass and stop bands. Unlike the Linear
Phase filter, group delay is not constant; however, phase shift is low and
the particular benefit with this filter is that the impulse response exhibits
no pre-ringing.
0
0
20
40
60
80
100
120
140
160
180
Impulse response
Time (samples)
Am
plitude
Steep filter
Magnitude (dB)
Frequency response
frequency/FS (input sampling rate)
-80
-60
-40
-20
0
20
-200
-180
-160
-140
-120
-100
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Steep filter
Linear phase filter
Our Steep filter is a linear phase filter that has been optimised for stop
band attenuation of close-in aliasing images. Here we have traded a
little attenuation of the very highest frequency response (-2dB at 20kHz
for 44.1kHz material) and a little more pre- and post-ringing for a very
steep attenuation just outside the pass band. The Steep filter is able
to attenuate aliasing at 22kHz by some 80dB for 44.1kHz material for
instance.
0
0
20
40
60
80
100
120
140
160
180
Impulse response
Time (samples)
Am
plitude
Note:
All filters exhibit the same ultimate roll-off of approximately 140dB.
The following table shows the filter stop band attenuation for 44.1kHz
material:
Linear Phase
Minimum Phase Steep
Roll-off at
20kHz
-0.1dB
-0.1dB
-2dB
Roll-off at
22kHz
-10dB
-10dB
-82dB
Ultimate roll-off 140dB
140dB
140dB
We encourage you to experiment with the filters to determine which
sound best to your ears and using your source equipment/programme
material. The 851D remembers and recalls the selected filter type for
each input individually, making it possible, for example, to select Steep
for the USB input and Linear Phase for Digital Input 1, and so on.
