Filter Cleaning; Input Sensitivity And Ground Lift Switches - Macro-Tech 24x6 Reference Manual

function normally (remain off if no signal is present;
flash if a signal is present).
4. After the mute delay, turn up the level of your audio
source to the maximum desired level.
5. Turn up the level controls of the amplifier until the
maximum desired sound level is achieved.
6. Turn down the level of your audio source to its
normal range.
For ease of use, the Level controls are also located on
the front panel. Each control has 31 detents for accu-
rate repeatability. To prevent tampering with these con-
trols, the Level Control Security Kit is available (see
Section 8.2).
The Input Sensitivity switch is located inside the PIP
compartment at the back of the amplifier. It is factory-
set to 0.775 V for rated output into 8 ohms.* If desired, it
can be switched to 1.4 V for rated output into 8 ohms, or
to a fixed voltage gain of 26 dB. At 26 dB voltage gain,
the equivalent input sensitivity is: Macro-Tech 24x6: 3.1
and 2.2 V for Channel 1 and 2, respectively. Macro-Tech
36x12: 4.8 and 2.6 V for Channel 1 and 2, respectively.
To change the input sensitivity:
1. Turn off the amplifier and disconnect its power
cord from the AC mains power receptacle.
2. Remove the PIP module (two screws).
3. Locate the sensitivity switch access hole inside
the chassis opening as shown in Figure 4.3. It is
located just above the phone jack inputs.
4. Set the switch to the desired position noted on the
access hole label. (Move the switch toward the
front panel to set the input sensitivity to 1.4 V for
rated output power, move it to the middle position
for a voltage gain of 26 dB, or move it toward the
back panel to set the input sensitivity to 0.775 V.)
5. Replace the PIP module and connect the power.
The Ground Lift switch is located on the back panel
and can provide isolation between the input signal
grounds and the AC (chassis) ground. It affects only
the phone jack inputs and has no affect on the PIP mod-
ule input connectors. Sliding the switch to the left iso-
lates or "lifts" the grounds by placing an impedance
between the sleeve of each input phone jack and the
AC power ground.
The noninverted and inverted signal lines for the PIP
module are connected in parallel with the correspond-
ing lines of the phone jack inputs. The input signal
grounds are not paralleled. Specifically, XLR pins 2 and
3 are connected in parallel with the tip and ring of the
* Factory setting for international models is 1.4 V.
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Macro-Tech
Fig. 4.3 Input Sensitivity and Ground Lift Switches
corresponding phone jack. However, pin 1 of the XLR is
not connected in parallel with the sleeve of the phone
jack. This makes it possible for a PIP module to handle
its own signal grounds independently.
The Reset switches for the power supply circuit break-
ers are located on the back panel. The circuit breakers
protect the power supplies against damage in cases
where excessive current is being drawn from the AC
mains. If a breaker trips, the IOC indicator for the af-
fected channel(s) will turn on and the Enable indicator
will remain on. To reset a breaker:
1. Turn off the Enable switch.
2. Press the breaker's reset switch.
3. Turn the amplifier back on.
Contact an authorized service center or Crown's Tech-
nical Support Group if the problem persists.

4.5 Filter Cleaning

Dust filters are provided on the air intakes to the cooling
system (Figure 2.1). If this filter becomes clogged, the
unit may not cool as efficiently as it should which might
produce lower-than-normal output levels due to high
heat diffuser temperature.
To clean, remove each of the filter elements by gently
pulling them away from the front panel. Clean with mild
dishwashing detergent and warm water. Replacement
filters may be ordered from the factory.
Dust filters are not 100% efficient—depending on the
local environment, the internal heat sinks of the ampliifer
will benefit from periodic cleaning by a qualified techni-
cian. Internal cleaning information is available from our
Technical Support Group.
® 24x6 & 36x12 Power Amplifiers
Reference Manual