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Setting Mic/Line Input and Mix Levels
In this example, the mic/line input 1 signal is sent to output 1 (see figure 58 on page 88).
To set the mic/line input and mix levels:
1. Connect a microphone to input #1.
2. Double-click the mix-point (
c
) for mic/line 1 to output 1 to open the dialog for that
mix-point, then unmute the mix-point to place the signal into the mix.
The default level for the mix-point is 0dB, or unity gain.
3. Open the Input 1 Gain (
a
) dialog and set gain to 0dB (turn on phantom power if the
mic requires it), then unmute the channel.
4. While testing the mic, raise the fader level until the mic is clearly audible. The amount
of gain and the meter level vary at this point, but as a general guideline the input
gain level should be at 40 to 50dB, with the meter averaging somewhere around
– 20dBFS.
Ideally, audio will be optimized here, but voice levels at microphone inputs can vary greatly.
Having the meters average around – 20dBFS allows enough headroom to accommodate
sudden changes to voice levels. Further adjustment can be necessary.
Adjusting Trim
This is where setting gain structure becomes a balancing act. The following sections
provide guidelines, but it can take a bit of going back and forth to correctly set levels for
the installation. For example, output level can be controlled and kept below clipping using
a compressor or limiter in the output dynamics block. However, adjusting the post-matrix
trim will affect how the compressor or limiter works.
1. Apply program material (or pink noise) at the input to be adjusted.
2. Open the output Volume (
e
) and post-matrix Trim (
d
) dialog boxes.
3. Set output volume to 100% (mute if necessary).
4. Adjust the post-matrix trim until the meter level in the output volume dialog is below
clipping (or ideally, matches the level at the input gain meter).
This maintains the audio at an optimal level in the output signal chain while preventing
clipping at the output.
Setting Volume Control for the Amplifier Stage
The maximum output of the DMP64 is +21dBu. As an example, assume the maximum
input level of a power amp is +4dBu with its input attenuator fully open. If using the
output Volume control (
e
) of the DMP64 to control volume levels, turn down the input
attenuator of the power amp the equivalent of 17dB (21 – 4 = 17) to ensure clipping does
not occur at the amplifier. That puts the amplifiers input level at –13dB (+4 – 17=–13).
If the amplifier setting (when the output volume controls of the DMP64 are at maximum)
is too loud for the room, it can need to be reduced further. If it is not loud enough for the
room, a more powerful amplifier can be required.
Extron recommends using the output volume or post-mixer trim control on the DMP64
for controlling output volume. When using loudness processing on the unit, it only works
in conjunction with these controls.
When using the power amplifier input attenuation to control volume (using the same
power amp maximum input level), set the output volume or post-mixer trim control of the
DMP64 to –17dB. This is another way that clip points of the two devices are matched.
Verify the amplifier is not clipping by observing the amplifier clip indicator.
NOTE: Using the amplifier input attenuation to control volume compromises the
signal-to-noise ratio of the DMP64 and is not recommended.
DMP64 • Software Control 91