Bose AV28, Manual

Page: 19 / 73

19
Theory of Operation
A hardware issue was found with the CS4224 codecs whereby audio passing through its A/D
converter emerges with left/right sample pairs mismatched; specifically, with left samples lagging
right samples by one sample clock. In other words, left/right sample pairs coming out of the ADC
together were not sampled together (right was sampled before left). The codec’s DAC section has
the reverse problem: left samples will emerge ahead of the associated right samples. The net result
of this hardware bug is that audio passed fully through the codec (from ADC input to DAC output)
will have no improper left/right delays. However, audio passed only partially through the codec
(only the ADC section, for example) will have left/right pairs emerge slightly out of phase. This
slight phase difference will have no noticeable effect when played through conventional stereo
speakers; however, slight spatial anomalies might be noticed if played through a surround-sound
system.
When playing-back an audio stream which was recorded using pre-emphasis (common in earlier
CD’s, for example), the media center’s analog Record Outputs will not properly apply de-emphasis,
as follows. The resulting audio will have more treble than desired:
Playing-Back Pre-Emphasized Audio Streams
Source Playing Zone 1
S/PDIF
Network
Output
(Used for
Cobalt II)
Zone 1
Variable
Analog
Output
(Used for
Cobalt I)
Analog
Record
Output
S/PDIF
Record
Output
Headpho
ne
Output
Zone 2
S/PDIF
Network
Output
(Used for
Cobalt II)
Zone 2
Variable
Analog
Output
(Used for
Cobalt I)
Internal CD-DA
O.K. O.K. De-
Emphasis
is Missing
O.K. O.K. O.K. O.K.
External S/PDIF
Sources
O.K. O.K. De-
Emphasis
is Missing
O.K. O.K. O.K. O.K.
CS4224 Hardware Bug: Effect on Postman Console Audio Outputs
Source Playing Zone 1
S/PDIF
Network
Output
(Used for
Cobalt II)
Zone 1
Variable
Analog
Output
(Used for
Cobalt I)
Analog
Record
Output
S/PDIF
Record
Output
Headphone
Output
Zone 2
S/PDIF
Network
Output
(Used for
Cobalt II)
Zone 2
Variable
Analog
Output
(Used for
Cobalt I)
Internal DVD Disc Left/Right
O.K.
Left/Right
O.K.
Right
Leads Left
Left/Right
O.K.
Left/Right
O.K.
Left/Right
O.K.
Left/Right
O.K.
Internal CD-DA
Left/Right
O.K.
Left/Right
O.K.
Right
Leads Left
Left/Right
O.K.
Left/Right
O.K.
Left/Right
O.K.
Left/Right
O.K.
Internal MP3 Disc Left/Right
O.K.
Left/Right
O.K.
Right
Leads Left
Left/Right
O.K.
Left/Right
O.K.
Left/Right
O.K.
Left/Right
O.K.
Internal AM/FM
Right
Leads Left
Left/Right
O.K.
Right
Leads Left
Right
Leads Left
Left/Right
O.K.
Right
Leads Left
Left/Right
O.K.
External S/PDIF
Sources
Left/Right
O.K.
Left/Right
O.K.
Right
Leads Left
Left/Right
O.K.
Left/Right
O.K.
Left/Right
O.K.
Left/Right
O.K.
External Analog
Sources
Right
Leads Left
Left/Right
O.K.
Right
Leads Left
Right
Leads Left
Left/Right
O.K.
Right
Leads Left
Left/Right
O.K.