Technical information

Macro-Tech 3600VZ Power Amplifier
Page 22
0.77 V
26 dB
SENSITIVITY SWITCH INSIDE ACCESS HOLE
INPUT GROUND LIFT SWITCH
1.4 V
UNBALANCED
INPUT WIRING
BALANCED
INPUT WIRING
THIS AMPLIFIER IS EQUIPPED WITH SELECTABLE INPUT SENSITIVITY. REMOVE P.I.P. MODULE TO ACCESS SENSITIVITY SWITCH.
CH-2 CH-1
+
–
TIP
RING
SLEEVE
GND
INPUT GROUND LIFT
LIFT
+
TIP
SLEEVE
GND
(AFFECTS PHONE INPUTS ONLY.)
INPUTS
(MONO)
Fig. 4.3 Input Sensitivity and Ground Lift Switches
most other severe conditions. The breaker can also
trip in situations where extremely low-impedance loads
and sustained high output levels result in current draw
that exceeds the breaker’s rating. Again, this should
only be possible when operating outside rated condi-
tions or when an input signal is clipped severely.
4.4 Controls
The Enable switch is located on the front panel so you
can easily turn the amplifier on and off. If you ever need
to make wiring or other installation changes, don’t for-
get to disconnect the power cord. The six steps listed
next should be followed whenever you turn on the am-
plifier.
1. Turn down the level of your audio source. For
example, set your master mixer’s volume to –∞.
2. Turn down the Level controls of the amplifier (if
they are not already down).
3. Turn on the Enable switch. The Enable indicator
beside the switch should glow. During the four
second mute delay which immediately follows,
the Signal/I OC indicators may flash unpredict-
ably and the ODEP LEDs will stay off. After the
mute delay, the ODEP indicators should come
on with full brilliance and the Signal/ IOC indica-
tors should function normally (remain off if no
signal is present; flash if a signal is present). Re-
member, the Channel 2 Signal/ IOC indicator re-
mains on if the amplifier is in Parallel-Mono
mode.
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 located on the
front panel. Each control has 31 detents for accuracy.
To secure these controls, the Level Control Security Kit
is available (see Section 8.2). Note: In Bridge-Mono or
Parallel-Mono mode, turn down the Channel 2 Level
control and only use the Channel 1 control.
The Input Sensitivity Switch is located inside the
back of the amplifier (Figure 4.3). It is set at the factory
to 0.775 volts for rated output into 8 ohms. It can also
be switched to a sensitivity of 1.4 volts, or a fixed volt-
age gain of 26 dB (4.8 volts for rated output).
How to change the input sensitivity:
1. Turn off the amplifier and disconnect its power
cord from the AC mains power receptacle.
2. Remove the P.I.P. 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.
Note: The Sensitivity switch will not be visible
because it is mounted below the hole. Use your
little finger to reach it.
4. Set the switch to the desired position noted on
the access hole label. The position toward the
front panel sets the sensitivity to 1.4 volts for
rated output, the middle position provides a
voltage gain of 26 dB, and the position toward
the back panel sets the sensitivity to 0.775 volts
for rated output.
5. Replace the P.I.P. module and restore the power.
The Input Ground Lift switch is located on the rear
panel (Figure 4.3) and can provide isolation between
the input signal ground and the AC ground. It affects
only the phone jack inputs and has no affect on the
input connectors on the P.I.P. module. Sliding the switch
to the left isolates or “lifts” the grounds by placing an
impedance between the sleeve of each phone jack
and the circuit ground.
When a P.I.P. module is plugged into the amplifier, only
the noninverted and inverted signal lines are con-
nected in parallel with the corresponding lines of the
input phone jacks. The signal grounds are not paral-
leled. For example, XLR pins 2 and 3 are connected in
parallel with the tip and ring of the corresponding
phone jack. However, pin 1 of the XLR is not connected
in parallel with the sleeve of the phone jack.