Lectrosonics DMPA12 User Manual download pdf (Page 15)

DMPA12 Installation Guide

Rio Rancho, NM

Adjust the Gain / Level

The default setting on the ampliﬁer is OFF, so no signal

will be passed to the outputs until a value is selected.

Values can be entered directly into the ﬁeld, or the val-

ues can be scrolled up and down with mouse clicks.

The multi-colored bar graphs indicate the signal levels

at the outputs. The LEDs indicate yellow for compres-

sion and red for limiting.

About the Level Meter

The bar graph is a true RMS level meter which displays

the output audio level in dBu after digital signal process-

ing 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.

Initial Setup Hints

1) The GUI interface is quite intuitive. As a recom-

mended ﬁrst step, we suggest you select Labels

from the Menu Bar and type in a description of each

output. This will simplify further setup steps be-

cause you will be able to easily keep track of which

output you are adjusting.

2) The right mouse click is handy in this interface by

allowing Copy, Paste, Delete, Undo and Select All

operations on the values presented in the ﬁelds.

3) Store startup settings in a startup default preset.

(See Storing and Recalling Presets in the online

HELP application.)

4) Presets will take about 3 seconds to switch due to

the many parameters in the unit - audio will switch

off temporarily during a preset switch to avoid feed-

back. If you need quicker response with no inter-

ruption to the audio, use macros instead - try using

the macro recorder for making any changes. The

only changes that cannot be made in a macro are

ﬁlter adjustments. such as EQ.

5) Store presets after changes are made and not be-

fore they are made.

6) Help is always available by clicking Help on the

Main Menu Bar. This Help is a comprehensive

resource and includes the latest revisions to the

software and ﬁrmware.

IMPORTANT: Any changes made during setup

must be saved in the unit via the preset menu.

For direct support from the factory, call 1-800-821-1121.

Ask for anyone in the SALES department. They will be

able to answer your setup and/or technical questions or

will get the correct person who can help on the phone.

The Gain / Level tab is used to to adjust and monitor

the outputs. The GUI presents a multi-color bar graph

and LED for each of the 12 outputs.

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Lectrosonics DMPA12 User Manual Page 15

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