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Macro-Tech 600/1200/2400 Power Amplifiers
4 Operation
4.1 Precautions
Macro-Tech amplifiers are protected from internal and
external faults, but you should still take the follow pre-
cautions for optimum performance and safety:
1. Improper wiring for Stereo, Bridge-Mono and
Parallel-Mono modes can result in serious oper-
ating difficulties. Refer to Section 3.3 for details.
2. WARNING: Do not change the position of the
stereo/mono switch unless the amplifier is first
turned off.
3. CAUTION: In Parallel-Mono mode, a jumper is
used between the red (+) Channel 1 and 2 output
binding posts. Be sure to remove this jumper for
Stereo or Bridge-Mono mode, otherwise high
distortion and excessive heating will definitely
occur. Check the stereo/mono switch on the back
panel for proper position.
4. Turn off the amplifier and unplug it from the AC
mains before removing the PIP card.
5. Use care when making connections, selecting sig-
nal sources and controlling the output level. The
load you save may be your own.
6. Do not short the ground lead of an output cable to
the input signal ground. This may form a ground
loop and cause oscillations.
7. Operate the amplifier from AC mains of not more
than 10% variation above or below the selected line
voltage and only the specified line frequency.
8. Never connect the output to a power supply out-
put, battery or power main. Such connections
may result in electrical shock.
9. Tampering with the circuitry by unqualified person-
nel, or making unauthorized circuit changes invali-
dates the warranty.
Remember: Crown is not liable for damage that results
from overdriving other system components.
4.2 Indicators
The amber Enable indicator is provided to show that
the amplifier has been turned on (or enabled), and that
its low-voltage power supply and forced-air cooling sys-
tem are working. It does not indicate the status of the
high-voltage power supplies. For example, the Enable
indicator will remain lit during unusual conditions that
would cause the amplifier's protection systems to put a
Reference Manual
Fig. 4.1 Indicators
high-voltage power supply in "standby" mode (see
Section 4.3).
The amber ODEP indicators confirm the normal op-
eration of Crown's patented Output Device Emulation
Protection circuitry. During normal operation, they glow
brightly to show the presence of reserve thermal-dy-
namic energy. They dim proportionally as the energy
reserve decreases. In the rare event that there is no
reserve, the indicators turn off and ODEP proportion-
ally limits the drive level of the output stages so the am-
plifier can continue safe operation even when
conditions are severe. (For a more detailed description
of ODEP, see Section 4.3.1.)
The ODEP indicator for the affected channel will turn off
if a high-voltage power supply is put in "standby" mode,
a high-voltage power supply fuse (or breaker) blows,
or a transformer activates its thermal protection circuitry
(see Section 4.3.2). Both ODEP indicators turn off if the
amplifier loses AC power, the power switch is turned off
or the low-voltage power supply fuse blows.
The green Signal/IOC indicators show signal pres-
ence, distortion and input overload. As signal presence
indicators, they flash with normal intensity in sync with
the output audio signals. As IOC (Input/Output Com-
parator) indicators, they flash brightly if there is any dif-
ference between the input and output signal waveforms
greater than 0.05%. Because transient distortion hap-
pens quickly, a 0.1 second "hold delay" keeps the indi-
cators on long enough to be easily noticed. The IOC
function essentially provides proof of distortion-free per-
formance . As input overload indicators, they flash
brightly with a 0.5 second hold delay to show that an
input signal is too large and must be clipped at the in-
put. Note: The Channel 2 IOC indicator will remain lit
when running in Parallel-Mono mode.
Under abnormal conditions where one of the amplifier's
high-voltage power supplies is temporarily put in
standby mode, the Signal/IOC indicators will stay on
with full brightness. They will resume normal operation
when the amplifier is no longer in standby mode.
Page 19
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