Extron electronic DMP 64 manual Setting Mic/Line Input and Mix Levels, Adjusting Trim

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 0 dB, or unity gain.

3.Open the Input 1 Gain (A) dialog and set gain to 0 dB (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 50 dB, with the meter averaging somewhere around – 20 dBFS.

Ideally, audio will be optimized here, but voice levels at microphone inputs can vary greatly. Having the meters average around – 20 dBFS 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 DMP 64 is +21 dBu. As an example, assume the maximum input level of a power amp is +4 dBu with its input attenuator fully open. If using the output Volume control (E) of the DMP 64 to control volume levels, turn down the input attenuator of the power amp the equivalent of 17 dB (21 – 4 = 17) to ensure clipping does not occur at the amplifier. That puts the amplifiers input level at –13 dB (+4 – 17 = –13).

If the amplifier setting (when the output volume controls of the DMP 64 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 DMP 64 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 DMP 64 to –17 dB. 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 DMP 64 and is not recommended.

DMP 64 • Software Control 91