User manual

dCS 950 / 952 User Manual Manual for Software Version 6.2x
dCS Ltd 22
nd
May 2000
Manual part no: DOC0029526B1 Page 35 Document No: OS-MA-D0002-952.6B1
Contact dCS on + 44 1799 531 999 email to: [e-mail]
(inside the UK replace + 44 with 0) web site: www.dcsltd.co.uk
Frequency Response
The overall frequency response is determined by the sample rate, the digital
filter and the analogue filter. All filters must cut-off before Fs/2 is reached, with a
margin to allow for sufficient attenuation to be reached to effectively eliminate
Nyquist images.
At a sample rate of 44.1kS/s, a flat 20kHz pass band must be maintained with at
least 80dB of attenuation above Fs/2 (22.05kHz). This allows barely 2kHz
margin between the pass band and the stop band for the filter to do its work,
necessitating a very sharp filter.
At sample rates of 88.2kS/s and above, there is so much extra bandwidth
available that maintaining a flat 0 - 20kHz audio band is less of a problem. This
allows more relaxed filters to be used, resulting in extra sonic benefits.
Frequency responses for all 5 sample rates, set to Filt1, are shown below.
dCS 952 SW v6.20
-24
-18
-12
-6
0
6
0 10 20 30 40 50 60 70 80 90 100
Tone Frequency (kHz)
Level (dB)
96k88.2k48k
32k
44.1k
Figure 14 – Filter 1 frequency responses