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3.3
OPERATING
PRECAUTIONS
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The
following are a number of operating precau•
tions given as an aid to understanding proper and
improper amplifier
usage:
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1.
Use
care in making connections, selecting
signal sources, and controlling the output
level. The loudspeaker
you
save
may
be
your
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own.
CROWN
is not liable for any damage
done to loads due to careless amplifier usage
or deliberate overpowering. For pointers on
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load protection
see
Section 3.4.
2. Never parallel the two outputs
by
directly
tying them together
or
parallel them with any
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other amp's output. Such connection does not
result in increased power output. Damage in•
cur
red
by
such operation is not covered
by
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the warranty.
3. Never drive a transformer-coupled device or
any other device which appears
as
a low
fre
-
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quency short (less than 3 ohm)
without
a
seri
es
isolating capacitor. Such operations
may damage the device and/ or needlessly
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activate the V-1 lim
it
ing
(s
ee
Fig. 2-5).
4.
Do
not short the ground lead
of
an output ca•
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ble to the input signal ground
as
oscillations
may result from forming such a ground loop.
5.
Operate
and
fuse the amplifier only
as
set
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forth in section 3.2.
6.
Operate the amplifier from
AC
mains of not
more than 10% above the
se
lected line volt•
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age
and only on 50, 60
or
400Hz
AC.
Failing
to comply with these limits will also invali•
date the warranty.
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7. Never connect the output to a power supply
output, battery, or power main. Damage in•
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curred by such a hookup
is
not covered by
the warranty.
8.
Do
not
expose
the
amplifier
to corrosive
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chemica
ls such
as
soft drinks, lye,
sa
lt
water, etc.
9. The amplifier is not recommended for high
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power industrial usage at frequencies above
30KHz.
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19
10. Tampering in the cir
cuit
by unqualified per•
sonnel or the making
of
unauthorized circuit
modifications invalidates the warranty.
11.
Do
not expose the output leads to areas likely
to
be
struck
by
lightning. Such
an
installa•
tion could invalidate the amplifier.
3.4
LOAD
PROTECTION
METHODS
The most common of all protection schemes is a
fuse in
series
with the l
oad
. The fuse may
be
single, fusing the overall system.
Or,
in the case
of a multi-
way
speaker system,
it
may
be
multi·
pie with
one
fu
se
on each speaker.
Fuses
help to prevent damage due to prolonged
overload, but provide essentially
no
protection
against damage that may be done
by
large tran•
sients and such. To minimize this problem, high-
speed instrument fu
ses
such
as
Littlefuse 361000
series are most appropriate for such applications.
For
a
nomograph
showing fuse s
ize
vs
. loud-
speaker ratings refer
to
Fig
. 3-3.
4
s
400
4
300
s
:a
200
6
ISO
7
2
100
10
60
9
~
10
40;
N
:aof
12
~
20
U -
w -
-·
14
~ I
IS
~i
~i
16
::1:
-
10
rn
I
~
.:a
20
6 t
.2
4
2S
:a
,IS
:ao
2
.1
u
0
.GI
FIG. 3 • 3
FUSE SELECTOR
NOMOGRAPH
FOR
LOUDSPEAKER PROTECTION
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