Service manual
Bcrcrurn.
, , ,
Sfudjo Weference
Service
Manual
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R~K
0
-
k
to interrupt around
lw~=os
via
the
Ground
"
-
Studio
Referenee amplifiers utilize numerous
Crown
Lift
Switch.
The
non-inverting
(hot)
si&
of
the balanced
innovations, including gf@tuflded
bridge
and
ODEP
input
is
fed
to
the
non-hverting
input
of
the;
firs@
op-
teehnofogies.
Cooling
t~chniques
make
use
of
what
is
amp stage. The
inver"ring
(negative)
side
of the
bal-
essentially air conditianer technology.
Air
flows
bottom
ancsd input
is
fed
to
the
inverting
input
of
the
firswsp-
lo
top, and front to
side.
Air
ftsws
a
shafi
distance
amp stags.
A
potentiometer
is
provided
far
esmmon
across
a
wid@
heatsink.
This
type
of air flow pro.\rides
mod@
rejection adjnmstment
(R5f
2).
Electricaiiys the
BGS
significantly better emling than
the
"wind
$unnel'"tech-
is
at
unity
gain, (From an
audio
perspe~tive, however,
nology
used
by
many other manufacturers, Output
this
stage
actually provides
+6dB
gain
if
a
fully
bai-
transistors are
of
the
metal can
type,
rather
than
fh~
anced signal is
placsd
on
its
iraput.)
Tho
BGS
is
a
nsn-
plastic case
style.
This
alIo\~s
for
a significantly higher
thermal
margin
for
the given voltage
and
current rat-
ings.
Ail
devices
used
are tested
and
grad~d to en-
sure
maximum
reliability, Another electronic
technique
used
is
negative feedback. Almost
atl
power amplifi-
$put
sf
the
BGS,
the signal goes to
the
ers utilize n~gativa;. feedback
80
control
gain
and pro-
gain
is
determined
by
the
position
of the
vide
stabifity$
but
Crown
uses
multiple
nested
feed-
itch,
and
lev@/
is
detc~mined
by
the
level
back
imps
far
maximum
stability
and
greatly
impag>k/ed
s
an inverting stage
with
the
input
being
damping.
Studio Reference ampiifiers
have
damping
mp
stage. Because
gain
after this
stage
in
@XC$S$
af
20,000
in
the bass frequency range.
This
B
(factor
sf
2Q),
greater amplifier sensi-
feedback,
along
with
our compensation and
ut"l3-l~~
sd
$y
csntrosling the
ratio
of f~edback
distortion output tapol~gy~
make
Grown Studio
Ref-
nee,
The Sensitivity Switch sets the
in-
erence
amplifier superior*
put impedance to this stage
and
varies
the
gain such
that
the
overall
amplifier gain
is
26
dB,
or
is
adjusted
Fsatt~res
specific
to
the
Studio Reference
include:
A
or
0.775V
ar
d.4V
input
to
attain rated
high
power
toroidal Esansfsrmsr; Computer controlad,
varjable
speed,
whisper quiet
fan;
Built
in
AC
power
fiffes;
Soft
start
circuit
Za control inrush curroot;
Fuji
ov-
ervodtage and internal fault protection,
This
ampli-
tpuX
from
the
VGS
is
fed
to
the non-
fier can operate
in either
Bridgge;! or Parallel Mans mode,
the
Errof
Amp
op-amp
stage through
as
well
as
in
Dual
(stereo)
made,
A
sensitivity
switch
capacitor
$C
t
00)
and
input
resistor
a)lows seiectian
sf
input voltage
required
for
rated &rut-
output
is
led
back
via
the
negative
put.
Level
cnr-llr~ls are mounted
on
the front panel and
op
re~istor
(W
1Q3),
The
ratlo
of
feed-
are
of
the rotary type, Front
panel
indicators let
the
user
know the status
of
amplifier
enable,
QDEP9
signal
tpuWof
the
amplifier
at
26
dB,
Bi-
presence
(SP!),
and
distortion
(90C),
Alsa
included
on
revent averdriving the Error
Amp.
the
front panel is
a
five-segmet display Tor each chan-
mp
amplifies the difference
be-
riel
which
displays
either
dynamic
range
tn
dB
ar
aut-
ut
signals,
any
difference
in
the
put
level
in
dB,
two waveforms
will
produce
a near open loop gain
condition which,
in
turn,
results
in
high
peak auWpu&.
For
addiriauai
details s~fer to the specification section,
ths
Error
Amp,
called the Error
or
ta
the appficable WaFerence Manual,
Signal
(ES)
drives the Voltage Translators,
4.3
Front
End
Operation
The
front end
is
comprised
of
three
stages:
Balanced
Gain Stage
(BGS),
Variable
Gain
Stage
{VGS),
and
the Error Amp. Figure
42
shows
a
simplified
diagram
of the front
end and
voltage ampixfieation stages,
4-3,f
Balanced
Gain
Stage
(80%)
lnpk~t
ts
the
amplifier
is
balanced, The
shield
from
the
1/4"
inputs
may
be isolated
from
chassis ground
by
4.4
Voltage
Alnplifi~ation
The
Voltage
Translator
stage
separates
the
output
of
the Error
Amp
into
balanced positive and negative
drive
vol"s~ge?s
for
the Last bltage Amplifiers
(LVAS)~
translating the
signal
from ground referenced
n
15V
to
kV@c
referenee,
LVAS
provide the
rnak
voltage ampli-
fication
and
drive
the
High
Side
output stages.
Be-
muse there
is
a
slight
lass
of
gain
in
the
translator
stage,
the
gain
after the translatar
is
a
factor
of
25.2,
Cir~uit Theory
4-2