Filters - Cambridge Audio AZUR 851C User Manual

Operating instructions cont.
Setup
Menu structure

Auto Off Auto USB Input
Play Class Naming
On Off Audio 2 Audio 1
Off 5m 10m 15m Digital 1 Digital 2 AES/EBU
The 851C menu structure has a variety of setup parameters that can
be adjusted to suit both specific installation requirements and personal
preferences. The setup parameters are accessed and modified through
a menu driven interface that uses the 851C display along with its front
panel or handset Menu, Select, Skip ( ) and Stop () buttons.
To enter the 851C setup menu, first press the front panel or handset
Menu button. The first setup parameter (Auto Off), will be shown on the
display. To select further parameters for adjustment press the one of the
front panel or handset Skip ( ) buttons.
With the required parameter selected, press the front panel or handset
Select button. Pressing one of the Skip ( ) buttons will now scroll
through the options available for that parameter. When the required
option is displayed, press the front panel or handset Select button.
The setup option is now stored. To exit from the setup menu interface
press the front panel or handset Menu button to step back through the
interface.
Note: The 851C will automatically return to normal play mode if it is left
inactive in setup menu mode for more than a minute.
Each setup parameter and its options is described following paragraphs.
Auto Off – When Auto Off is engaged the 851C will switch to standby
after a preset time if no audio is playing. The Auto Off options are Off, 5
minutes, 10 minutes and 15 minutes.
Auto Play – WIth Auto Play engaged a CD will begin to play as soon as the
disc drawer is closed. The Auto Play options are Off and On.
USB Class – USB Class options enable 851C compatibility with both USB
Audio 1.0 and USB Audio 2.0 interface formats. The default setting is
USB Audio 1.0 which will work driverlessly with most operating systems
for 16-24 bit content at 32-96kHz. Note USB Audio 2.0 requires a driver
to be loaded for Windows. Without this selecting USB Audio 2.0 will
normally give no output . See section on USB Audio for advanced users.
Input Naming – Input Naming enables the display name of the Digital 1,
Digital 2 and AES/EBU inputs to be changed. Use the Skip ( ) and
Select button to select the input name to be changed. Once selected
a flashing cursor will appear beneath the first character to the existing
name. The Play/Pause and Stop () buttons can then be used to scroll
through the available characters. When each desired character is
displayed, use the Skip ( ) buttons to move on to the next character.
Press the Select button to store the new name.
S/W Version – Selecting S/W Version displays the player's internal
operating software version number and some additional build
information. This information is primarily provided for service personnel.
Front IR – Selecting Front IR enables the 851C front panel infrared
receiver to be switched on or off (if you are using an external IR system
and the IR emitter Input or Control Bus. In the majority of installations
the infrared receiver should be left switched on.
Digital Vol – Digital Volume enables the 851C to operate as a digital
preamplifier and be connected directly to a power amplifier. With Digital
Volume engaged, the remote handset volume buttons (symbols) will
control the 851C analogue output level. Digital Volume is disengaged
(Off) by default and should remain off in most 851C installations. It
should only be engaged (On) if the 851C is installed in an appropriately
configured audio system without a further downstream volume control.
Ch. Balance – Only enabled when Digital Volume is used. A balanced
control is implemented.
12

S/W Front IR Digital Ch.
Version Volume Balance
(Note: Only available
if Digital Volume is
enabled)
On Off Off On

Filters

The 851C DSP has three different Filter functions: Linear Phase,
Minimum Phase and Steep. All three filters are highly sophisticated

audiophile topologies, optimised specifically for audio playback. In our
opinion, these filters offer excellent sound quality but differ subtly in
optimisation, hence we've made all three available to you.
Note: For clarity, all diagrams show the theoretical response of the DSP
itself, excluding any analogue filtering at the DAC output or the anti-
aliasing filter applied during recording and/or mastering of the digital
source.
Linear Phase Filter
20
0
-20
-40
-60
-80
-100
-120
-140
-160
-180
-200
0 0.1 0.2
The Linear Phase filter is a highly regarded audio filter offering low ripple
in both the pass and stop bands, and what is known as constant group
delay. Constant group delay means that audio signals of all frequencies
are always delayed by the same amount when passing through the filter.
All audio is therefore fully time-coherent at the output.
The trade-off with this type of filter is that due to internal feed-forward
in the DSP, its impulse response will exhibit some pre-ringing. In other
words, when excited with a theoretical impulse, the output has both
a small amount of pre- and post-spike amplitude ringing (albeit well
damped).
0
0 20 40
Frequency response
0.3 0.4 0.5 0.6 0.7
Frequency response
Frequency response
60 80 100 120 140
Frequency response
0.8 0.9 1
160 180