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FRONT PANEL OPERATION
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CH. INPUT SECTION
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| РНАМТОМ
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'D PHANTOM power switch
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These switches turn the internal phantom power supply
o on and offi in 4 channel groups.
PEAK
Turning the switch on applies 48 V DC across pins 2 & 3 of the XLR-type input channel |
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connectors. Be sure to turn the power supply OFF when it is not in use. Since phantom
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power is not normally required for high-impedance sources, the phone jacks are not con-
nected to the power supply.
Even when the phantom power is turned off, each bank of four LO-Z inputs are connected
internally via resistors. This means that if an external phantom power supply is connected
to one input, the other three inputs will also be supplied with phantom powering.
The phantom powering for each four channel bank can be set so that it is permanently off
by setting an internal PCB jumper. In this case the front panel switch has no effect. See
your Yamaha dealer for full details.
IMPORTANT:
The phantom
power supply has no effect on balanced
dynamic
micro-
phones or line sources, even if left on. However, unbalanced sources, or transformers
with earthed center taps are liable to hum or even be damaged if connected to the phan-
tom power supply when it is on. If phantom power is left on when balanced dynamic mics
are used the channel will have very high level "pops" when the mic is connected or dis-
connected.
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(2) Phase (Polarity) Reverse switch
This switch reverses the phase of the XLR-type connectors. In the normal position (switch
up), pin 2 is positive (hot), and pin 3 is negative (cold), and input and output signals are
the same. Reverse phase by depressing this button, making pin 2 negative (cold) and pin
3 positive (hot).
This switch also affects the HI-Z phone jack input. With the switch in its normal position,
the jack tip is positive (hot), and the ring is negative (cold). With the switch depressed, the
tip is negative (cold), and the ring is positive (hot).
Out-of-phase signals are often caused by differing wiring configurations in microphone or
mixing console cables, especially due to differing national standards.
(3) PAD switch, GAIN control and PEAK LED
These offer complete control over the input sensitivity. The gain control continuously
adjusts the sensitivity of the transformerless head amplifier between -16 & -60 dB. If this
is insufficient, in the case of particularly high signal levels, depressing the pad switch will
insert a 20 dB attenuator before the head amplifier.
The red LED peak indicator lights whenever the post-EQ, pre-fader signal comes within 3
dB of clipping, warning the operator of impending channel overload. As a protective mea-
sure it is advisable, when inserting a signal into a channel, to set the gain control to mini-
mum, and gradually raise the setting to the required level.
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@ [80 HPF switch
Depressing this switch inserts an HPF in the input channel with a 12 dB/octave roll-off at
80 Hz. Useful for reducing low frequency noise such as AC mains hum and wind noise.
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