Operation - Crown D-45 Reference Manual

D-45 / D-75A Power Amplifiers
4. Using a soldering iron, change the appropriate
jumpers for the desired operating voltage (see Fig-
ure 2.3).
5. Install an appropriate fuse: 2 amp type 3AG for 100
or 120 VAC mains, and 1 amp type 3AG for 200,
220 or 240 VAC mains.

3 Operation

3.1 Precautions
Although your amplifier is well-protected from any ex-
ternal faults, we recommend that you take the follow-
ing precautions for safe operation:
1. When the level of an input source is uncertain,
or an audio component has not previously been
used with your amplifier, always begin with the
level controls at a minimum and gradually in-
crease them while monitoring the output level.
This helps to avoid possible loudspeaker blasts.
2. Don't forget, your amplifier does not have a turn-
on delay. Beware of turn-on transients from
other equipment ahead of the amplifier—always
turn the amplifier on after other equipment has
stabilized.
3. Turn off the amplifier and unplug it from the AC
mains before replacing the fuse, installing an in-
put sensitivity jumper or changing the position
of the dual/mono jumper.
4. There are important differences between dual
and mono wiring. Refer to Section 2.3.
5. Operate the amplifier with the correct fuse: 2
amp type 3AG for 100 or 120 VAC mains, and 1
amp type 3AG for 200, 220 or 240 VAC mains.
6. When driving transformer-coupled devices
(such as electrostatic loudspeakers) or other
loads of less than 3 ohms, install an isolating ca-
pacitor in series with the positive (+) output.
Such operation may damage the load and
needlessly activate the amplifier's V-I limiting.
7. Operate the amplifier with AC mains of no more
than 10% above the rated line voltage and at
the specified line frequency.
8. Never connect the output to a power supply
output, battery or power main. This can cause
electric shock and damage to the amplifier.
6. Carefully check all connections.
7. Repeat steps 1 and 2 in reverse order to reas-
semble the unit.
IMPORTANT: Only use 2 amp type 3AG fuses for
100 or 120 VAC operation, and 1 amp type 3AG fuses
for 200, 220 or 240 VAC operation.
9. Do not expose the amplifier to corrosive chemi-
cals such as soft drinks, lye, salt water, etc.
10. Never short an output ground lead to the input
signal ground or oscillations may result.
11. The D-45 and D-75A amplifiers are not recom-
mended for use at frequencies above 30 kHz.
12. Tampering with the circuitry or making unautho-
rized circuit changes may be hazardous and in-
validates all agency listings.
3.2 Indicators
Your amplifier has five front panel indicators. First, a
power indicator behind the front panel becomes vis-
ible when the unit is turned on and has power. A signal
indicator for each channel flashes when there is output
from the amplifier. The IOC (Input/Output Comparator)
indicators work like sensitive distortion meters and flash
when the amplifier causes any distortion of 0.05% or
more. The IOC indicators typically glow for about one
minute after the AC power is turned off.
30
CHANNEL 1
20
40
50 10
0
SIGNAL
S LEVEL
Fig. 3.1 Visible Indicators
3.3 Controls
A power switch and detented level controls are located
on the front panel. When you power up the amplifier,
remember that the unit does not have a turn-on delay.
Each channel has its own level control which is used to
adjust the desired output level. Both level controls are
used in dual mode, but only the channel 1 control
should be used in bridge-mono mode.
30
CHANNEL 2
40 20
50 10
IOC
0
LEVEL
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