Lectrosonics DMPA12, Справочное руководство

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Reference Manual
Rio Rancho, NM 2
Level meter
This is a true RMS level meter which displays the out-
put audio level in dBu after digital signal processing is
complete. The range of the meter is -40dBu to +20dBu,
referenced to the internal voltage scale prior to digital
to analog conversion and power amplification. Note:
The relationship between output level as indicated on
the level meter and power output into an 8 ohm load is
determined by these facts:
The maximum output of the digital to analog converter
(DAC) is 1 Vrms. So a full scale (+20 dBu) signal, after
digital to analog conversion, results in a 1 volt signal at
the input of the power amplifier.
The gain of the power amplifier stage is 20dB (for volt-
ages, a tenfold increase).
So a 1 kHz test tone shown by the level meter to have
a level of +20 dBu (full scale) will result in in a power
output of 12.5 watts into an 8 ohm resistive load. This is
because the full scale signal, after conversion, results
in a 1 volt input to the power amplifier. Since it has a
gain of 20dB, the power amplifier output is 10 volts,
developed across the 8 ohm load. From “power equals
voltage squared divided by resistance” we get 100/8 or
12.5 watts. A +10 dBu test tone will result in 1.25 watts,
a 0 dBu test tone will result in 0.125 watts, and so on.
Note: These numbers are based on “ideal” components,
including the load resistance. Variations in real-world
components will result in measured power varying by as
much as 0.5dB from calculated figures.
Compressor/Limiter status indicators
These display the compressor/limiter status for all out-
puts. If the compressor for a particular output channel
becomes active, the corresponding indicator is lit yellow.
If the limiter for that channel becomes active, the indica-
tor is lit red. If a fault is detected on the channel, the
indicator will blink yellow.
Right Click Options
Right clicking any of the
channel groups brings up
options in a popup window.
Output label
Channels may be as-
signed a custom label to
make it easier to under-
stand a setup. For ex-
ample, labels like Zone 3
or Cry room might usefully
replace the default labels Ch 1, Ch 2, etc. To do this,
right click on the channel group desired and choose
Output Label... from popup menu. This opens the Edit
Label dialog:
Simply type in the new label and press OK.
Output gain step size
The default step size when using the buttons to run the
gain up and down is 1dB. To change this right click on
the channel group desired and choose Output gain step
size... from the popup menu. This opens the Set Gain
Step Size dialog:
Simply select a new step size and press OK.
Pink Noise On
The pink noise generator can be turned on/off by right
clicking on the channel group desired and choosing
Pink Noise On to toggle the switch. If the pink noise
generator is on, the Pink Noise On menu item will be
checked, otherwise it is unchecked. This option will be
disabled if the test tone generator is turned on for the
output channel.
Test Tone On
The 1 kHz test tone generator can be turned on/off by
right clicking on the channel group desired and choos-
ing Test Tone On to toggle the switch. If the test tone
generator is on, the Test Tone On menu item will be
checked, otherwise it is unchecked. This option will be
disabled if the pink noise generator is turned on for the
output channel.
Mute Output
The output channel can be muted/unmuted by right
clicking on the channel group desired and choosing
Mute Output to toggle the mute state. If the channel is
muted, the Mute Output menu item will be checked,
otherwise it is unchecked. The mute control will change
state to confirm the action.
Invert Phase
The phase (polarity) of the output channel can be
changed by right clicking on the channel group desired
and choosing Invert Phase to toggle the phase invert
state. If the phase is inverted, the Invert Phase menu
item will be checked, otherwise it is unchecked. This
feature is useful to correct for reversals of wiring be-
tween the output connector and an installed speaker.
Master Output Gain
The gain controls for the output channels may be
ganged together so that a single master control can be
used to run them up and down. To do this, right click on
the on any channel group and choose Master Output
Gain... from popup menu. This opens the Master Output
Gain Control dialog:
Simply select which output channels you wish to control
and then adjust the gain with the buttons provided. Click
OK when done, the changes made using the master
gain control will remain in effect after the dialog is
closed.