Phoenix Gold pm1400 - Manual (Page 11)

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70V Distribution Systems
The pm1400 has sufficient output voltage capability in stereo mode to drive 70-volt distribution
systems without using a step-up transformer at the amplifier. In this configuration, the pm1400
delivers up to 475 watts per channel to the 70-volt system, depending on the impedance of the total
system. As with all 70-volt systems, transformers are still required at each loudspeaker. The
pm1400 can deliver 475 watts per channel into an 8 ohm impedance (61.6V line voltage). The price
for going direct is having to calculate the new transformer tap values at the new line voltage. Since
watts are proportional to the square of the voltage, compute the correction factor by taking the ratio
of the square of the line voltages. Then multiply each tap value by this correction factor. For example, choose
a transformer that has taps at 10W, 5W and 2.5W when used in a 70.7 volt distribution. Its new tap values
when used with a pm1400 are computed as follows:
When used in a 70V distribution system, this transformer’s new tap values are 7.6W, 3.8W and 1.9W. Note
that the 3dB power relationship between each tap still holds true. Similarly, maximum amplifier loading
occurs when the sum of the NEW tap values equals the amplifier’s output power (475W)
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 to the right of the input 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).
Level Defeat
The Level controls can be defeated with a switch located above the input panel. See page 12 for more
i n f o r m a t i o n .
Power ON Sequencing
The Sequencer allows remote turn-on of any number of pm1400 amplifiers (or other Carver Professional
amplifiers equipped with sequencing capability). In multiple amplifier applications, the power-on for each
2. Apply to tap value:
marked tap value * K=new tap value
10W *.7591 = 7.591W
5W *.7591 = 3.796W
2.5W *.7591 = 1.898W
1. Complete correction factor K:
K = 61.6V 2 /70.7V 2
K = .7591
Output Wiring (see your Carver Professional Dealer for information on Carver Professional Accessories)
Use heavy gauge wire for speaker connections. The greater the distance between the amplifier and
the speakers, the larger the diameter the wire should be to minimize power losses across the wire
and improve the damping of the speaker. Wire thickness specifications (or gauges) get larger as the
wire gets thinner; thus 14-gauge wire is thicker than 16-gauge wire. Use the following as a guide:
up to 25 ft. use 16 gauge, up to 40 ft. use 14 gauge, up to 60 ft. use 12 gauge, up to 100 ft. use 10
gauge, up to 150 ft. use 8 gauge, up to 250 ft. use 6 gauge.
This will insure that the resistance of the speaker wire is less than 5% of 4 ohms, resulting in a
transmission loss of less than 0.5 dB. The multi-way binding posts can accept spade lug, bare wire or banana
connections. Be sure that all the fine strands of the wire are twisted together and contained within the
connector. If even one strand is loose and can touch the adjacent terminal, a short circuit may result. Class I
(NEC) wiring must be used.
Polarity
Loudspeakers must be connected with consistent polarity for correct phasing between them. Incorrect phasing
will do no physical harm, but frequency response will be affected. The key is to make sure that both speakers
connected to the speaker terminals are hooked up the same way. Connect (–) at the speaker outputs to (–) on
the back of the speaker, and (+) at the speaker outputs to (+) on the back of the speaker.
Dual Mono
The Stereo/Mono switch is located on the Input Board which is connected to the input panel. Connect the input
signal to CH2 input (CH1 input becomes disabled). Connect the speakers to the Speaker Outputs on the amplifier
in the same way that you would for normal stereo operation. Both speaker outputs will carry the signal that is
connected to the CH2 input.
Bridged Mono
The Stereo / Mono switch is located on the Input Board which is connected to the input panel. Connect the
input signal to CH2 input (CH1 input becomes disabled). Connect the speaker(s) to the two (+) speaker
terminals. The CH2 (+) terminal is the hot (non-inverting) side, and the CH1 (+) terminal is the low (–,
inverting) side. When connected in this way, each channel “sees” one-half the impedance of the speaker that
is connected between them. If an 8 ohm speaker is used, each channel will see a 4 ohm load. Therefore it is
not recommended that any total speaker load lower than 8 ohms be connected in this mode of operation. Use
Dual Mono operation for lower impedances. Note: Be sure to set both of the input level controls to the exact
same setting for equal power distribution per channel. Switching the Level Defeat Switch off is a handy way
to insure that both channels are operating at the same level.
CAUTION: In bridged mono operation, the output connections are actually a balanced output c o n f i g u r a t i o n .
This means that both output conductors have voltage present (neither one should be grounded).
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