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~~~~~~
__________
~D~.7~5~PO~W~E~R
~ A~
M
~P~U~A~ER~
__________________
~
RE
~ V~.O
Input Wiring Tips
1.
Useonly shieldcdcablc:.
Thehlgherthedensity
of the
shield
(the oUler conductor). the better the
cable.
Spiral
wrapped
shic:ld
is not
recommended.
2.
Keep
unbalanced
cables as short as possible
-
avoid cable
lengths
greater
than
10
fcct.
(Long
Wlba.lanced
cables
may
have
noticeable high
-
frequency
loss and
an: at higher risk o
f
pick ing
up
inte
rference from othe
r
nearby
componenlS.)
3.
00 not run signal
cables
together
with
high-
level wiring such
as
loudspeaker
wires
or
AC
cords.
(This
greatly lessens the chance of
hwn or
noise
being
induced
or picked up from
asymmetrical groWld loops.)
4. Tum the
enlires),stemoffbeforcchanging any
connections
and tum
the level controls
all
the
way
down
before
powering the
system back up. Crown
is
not liable
for
damage
incurred
when
any
transducer
orcomponent is
overdriven.
frequencies
(and any unwanted
DC
Ihat
may
also be
present), place
a
capac
itor
in series
in
Ihe
input
signal
line. The
graph in
Figure
A.2
shows
how the
value of
the
capacitor
affects the frequency response. Use only
a
low·
leakage
paper,
mylar
or
tantalum
capacitor.
Fig.
A.2lnpur High
Pass
Filter
If
large
amounts of
ultrasonic
or
RF
(radio
frequcncy) are
found on
lhe input,
such
as bias from tape
recorders. etc
.•
place a
low· pass
filter
on lhe input.
While the highest
RF
levels
Ihat can
be
reasonably expected
may
not
damage
the amplifier, they
can bum out
tweeters
or
other
sensitive
loads,
activate
the
amplifier's
prOicctive
system
or
overload
the
controlled-slewing-rate
stage of
the
amp.
(This
latter
amp
stage provides
RF
overload
protection.)
A·2
Appendix
A
The
following
filters
arc
recommended for
such
silUations:
~"
I I
•
-
..
_~
.L
-
)@
I
.
""' "
•
,--
u_
~
,
.
~..;..
_ •
....
.1.
-
-
.
"I
)
@
.
-
, ,
-
•
•
,
,
,-
•
~
"
~..;..
..
"
,
l.
...
"";"@
"1
"
...
,
-
....
,
. .
~
..
---.
-
.....
_
.....
"
_
..
Fig.
A.3 RFJ
(Lowpass) Filter
•••
,.
~
Another problem to
prevent
is
ground
loops -
undesirable
currents
nowing
in a grounded
system,
possibly causing
hum in
the
output.
A
common
form of
loop
is
a
pair
of
input
cables
whose
area
is
subjected
to
a
magnetic
hum
field
.
To prevent ground
loops causing magnetic
induction,
lace both cables
together
along
their
length,
and away
from the
power
transform
er.
DO
NOT
CONNECT THE
INPlIT
AND OlITPUTGROUNDS
TOGETHER.
Yet
another
facet
of
this
problem
occurs
when input
and
output
grounds,
tied together as
in
testing
or
metering,
allow
feedback
oscillation from
load
current
flowing in
the
loop.
In
some systems,
even
the AC power line may
provide
this
feedback path.
Proper
grounding,
isolation of
inputs
and common
AC·line
devices
is good practice.
A.4 Output
Consider
the
power
handling
capacity
of
your load
before
connecting
it
to
the
amplifier.
Crown is
not
liable
for
damage incurred
at
any
transducer
due
L
O
its being
overpowered. The use
of
loudspeaker
protection
fuses is
highly recom
mended
(sec Section 3.3.4).
Please also
pay
dose
auention
to
the
Operating
Prcxautions
section
(SccLion4
.1).
Under
nonnal
stereo
conditions,
a
load
impedance less
than
four
ohms
should
not be used.
The
mon
itor
output
is
parallel
10
the
main
outputs
so
any
load connected
to
it,
such
as
headphones,
will affect
the
load
impedance.
Be
careful
when
wiring multiple transducers
to
a
channel.
(fwo
g·ohm
speakers
in
paral lel present an
impedance
of
4 ohms
whi
le the
same
two
speakers
in
series
have
a
16
ohm
impedance.)
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