Page 17
Reference Manual
Macro-Tech
®
24x6 & 36x12 Power Amplifiers
4 Operation
4.1 Precautions
Macro-Tech amplifiers are protected from internal and
external faults, but you should take the following pre-
cautions for optimum performance and safety:
1. WARNING: Never strap the outputs together
for Parallel-Mono operation! Never bridge the
outputs for Bridge-Mono operation!
The
Macro-Tech 24x6 and 36x12 cannot be used in
any mono mode.
2. Turn off the amplifier and unplug it from the
AC mains
before removing a PIP card.
2. Use care when making connections, selecting
signal sources and controlling the output level.
The load you save may be your own.
3. Do not short the ground lead of an output cable
to the input signal ground. This may form a
ground loop and cause oscillations.
4. Operate the amplifier from AC mains of not more
than 10% variation above or below the selected
line voltage and only the specified line fre-
quency.
5. Never connect the output to a power supply
output, battery or power main.
Such connec-
tions may result in electrical shock.
6. Tampering with the circuitry by unqualified per-
sonnel or unauthorized circuit changes invali-
dates the warranty.
Remember: Crown is not liable for any damage result-
ing from overdriving other components in your system.
4.2 Indicators
The front panel has several helpful indicator LEDs.
The amber
Enable indicator
is provided to show 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 supplies. For example, the Enable indica-
tor will remain lit during unusual conditions that would
cause the amplifier’s protection systems to put a high-
voltage 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 re-
serve, the indicators turn off and ODEP proportionally
limits the drive level of the output stages so the ampli-
fier 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 provides
proof of distortion-free performance.
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 input.
Under conditions where one of the amplifier’s high-volt-
age power supplies is temporarily put in standby mode,
the Signal/IOC indicators will stay on with full bright-
ness. They will resume normal operation when the am-
plifier is no longer in standby mode.
The table in Figure 4.2 shows the possible states for the
ODEP and Signal/IOC indicators. It also describes the
conditions that may be associated with the different in-
dicator states. The Enable indicator will be off with the
first indicator state, “There is no power to the amplifier.”
All other conditions in the table will occur with the En-
able indicator turned on. It is important to note the pos-
sible states of the indicators in the rare event that you
experience a problem. This can greatly aid in determin-
ing the source of problems. Please contact your local
Crown representative or our Technical Support Group
for further assistance.
Fig. 4.1 Indicators
