Phoenix Gold pt1800 - Manual (Page 16)

70V Distribution Systems
The pt1250 has sufficient output voltage capability in stereo mode to drive 70-volt distribution systems without
using a step-up transformer at the amplifier. The amplifier delivers 300-watts per channel to the 70-volt system.
Transformers are still required at each loudspeaker (as is the case with all 70-volt systems). By re-calculating the
tap power ratings on the step-down transformers used at the loudspeaker end, the pt1250 can deliver additional
power beyond 300 watts.
Clipping Eliminator
This circuit prevents the input signal from exceeding the point where it would drive the amplifier into hard
clipping. It has no effect on the signal until it reaches the point where clipping would occur. The larger the input signal the
more the signal is reduced to keep the output just below clipping. The Clipping Eliminator circuitry is inactive when the
unit is shipped from the factory, but can be activated with the Clipping Eliminator Switch located on the front panel.
Note: If the Input Level control(s) are turned down far enough, a sufficiently large input signal can drive the input
differential amplifier into clipping. The Clipping Eliminator circuit cannot remedy this kind of clipping. Likewise, it has
no effect on clipping that occurs prior to the amplifier inputs (at the mixer or equalizer stage, for example).
pt1800/2400Installation
Location and General Precautions
Observe the following precautions when choosing a location for your amplifier.
A. Do not expose the unit to rain or moisture. If a fluid or foreign object should enter the unit, disconnect the power plug
and contact an authorized dealer or service center. Do not pull out the plug by pulling on the cord; grasp the plug firmly.
B. Protect from heat and allow adequate ventilation. Place away from direct sources of heat, such as heating vents and
radiators. All components produce some heat during operation, so make sure that the ventilation holes are not covered and
that air is allowed to circulate freely behind, beside and above the unit. Excessive heat is the single greatest source of both
short-term and long-term component failure.
Mechanical Considerations
The pt1800 and pt2400 requires three rack space units (5.25”) and a depth of 12.75” inside the rack, including the rear
supports. Secure the unit mechanically using four screws with washers to prevent marring the front panel. Neoprene rubber
washers are a good choice because they grip the screw head and prevent them from backing out when vibrated or transported.
Rear Support for Road Applications
In portable racks it is mandatory that the rear of the chassis be supported. The amplifier’s rear rack supports are equipped
with slots that can be used to support the rear of the chassis.
Thermal Considerations
The amplifier’s heat dissipation is thermally managed by a two speed fan that produces air flow from the back to front. Side
vents also move air within the chassis that effectively cool power supply components. It is essential that intake and exhaust
areas of the amplifier be kept clear for maximum performance. The pt2400/pt1800 amplifiers may be stacked directly on
top of each other without the use of spacer panels. Additional fans may be required in the rack if convection cooled (no
fan) amplifiers are used within the same rack as the pt1800/pt2400 amplifiers. Always mount convection cooled amplifiers
above the fan cooled amplifiers. Additional fans in the rack will reduce the amount of preheated air entering the fan cooled
models.
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