Input
Stages
and
switching
Circuit
pages
2
and
3
The
inputs
are
split
into
two
groups
with
the
Wolfson
SPDIF
receiver
at
location
IC201
dealing
with
Optical
and
Coaxial
selection
whilst
the
MUX
at
locations
IC202A
IC202B
and
IC205A
switch
between
SPDIF
(opt
or
coax)
and
USB
or
KLEER
under
control
from
main
micro.
SPDIF
input
The
Wolfson
WM8805
SPDIF
receiver
supplies
data
in
a
format
of
Data
,
LRCLK,
BCLK
and
MLCK,
the
output
of
IC201
runs
directly
to
the
DAC
via
the
MUX
at
location
IC202A
with
exception
of
the
MCLK
this
take
a
path
thru
IC203
as
part
of
the
MCLK
MUX
between
USB
/
KLEER
and
SPDIF
MCLK’s.
USB
input
The
USB
data
arrives
at
CON100
before
traveling
to
the
USB
streaming
control
chip
at
location
IC103
via
the
ESD
protection
Chip
at
location
IC101
the
chip
is
loaded
with
the
DCS
asynchronous/isochronous
input
system
from
IC100
at
boot
up.
IC103
has
it
own
MCLK
source
at
location
IC204
another
WM8805
this
time
used
as
an
adaptive
clock
source
the
output
is
buffered
by
IC203C
The
Data
,
LRCLK,
BCLK
are
switched
to
the
DAC
via
IC202B
with
the
MCLK
coming
via
IC203.
DAC
and
Audio
Stages
circuit
page
4
The
Wolfson
8741
DAC
can
be
found
at
location
IC301
and
takes
its
supplies
from
3V3D
and
5VDAC,
data
enters
the
chip
on
pins
1
–
5
and
should
be
seen
as
below.
Analogue
audio
leaves
the
DAC
as
balanced
pairs
on
pins
16
/
17
(left)
and
12
/
13
(right)
audio
then
travels
thru
and
filter
network
enters
the
Op
‐
amp
at
location
IC300
a/b
(L/R)
and
then
onto
IC302
a/b
(L/R)
output
muting
is
twofold
with
both
DAC
mute
(transistor
mute)
and
full
mute
(relay)
the
DAC
mute
is
provided
by
transistors
TR302
and
TR305
switching
the
audio
down
to
0v
this
under
the
control
of
the
DAC
MUTE
line
from
IC107,
the
relay
mute
is
provided
by
RLY300
and
triggered
from
2
lines
one
being
the
power
detect
sourced
from
D400
at
power
In
–
under
low
power
the
relay
will
close
at
5.3v
D.C
and
is
flipped
by
IC105
in
combination
with
IC104
the
output
of
IC104
is
low
to
mute
the
relay
is
switched
by
TR300.
Pin
loc
Signal
type
Pin
1
LRCK
Pin
2
SDATA
Pin
3
BCK
Pin
5
MCLK
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