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level DAC will then be fed from that new source. The DAC output level is set to 0dB as the default value on a new
m904 system, but this can easily be changed in CAL mode (see Accessing Cal Modes).
mUTe all mode
The MUTE switch is located to the immediate left of the mono switch. When this switch is pressed, all audio
output is muted, or cut, from the control room monitors. Note that mute will not affect the audio feed to the
headphone outputs.
When the MUTE switch is pressed, mute mode becomes active and the switch LED lights solid. When pressed
again, mute is exited and the switch LED is extinguished.
mono mode
Mono mode is used to sum the left and right channels of a stereo source to check for mono compatibility. This
feature monos both the control room speaker output as well as the headphone output. The mono mode switch
is located immediately to the right of the MUTE switch. When pressed, mono mode becomes active and the
switch LED lights solid. When pressed again, the mode is exited and the switch LED is extinguished.
dim mode
The dim switch, located to the right of the mono switch, is used to dim, or reduce, the control room output
levels by a fixed dB amount. The default value for this is -20dB but this value can be changed in CAL mode (dis-
cussed below). Dim values can be set between -5 to -35 in 5dB steps. Dim will not affect the audio feed to the
headphone outputs.
When the dim switch is pressed, dim mode becomes active and the switch LED lights solid. When pressed again,
dim is exited and the switch LED is extinguished.
UsinG The TalKbacK FeaTURe
The m904 provides a balanced talkback microphone input on the rear panel via a female XLR connector. Af-
ter you’ve plugged in a talkback mic, you can set the gain for the mic preamp, turn on 48v phantom power (if
needed) and set the talkback switch mode.
Note
: when you first power-up a new m904, the talkback mic pre-
amp gain will be set to +33dB, 48v will be set to ‘off’ and talkback switch mode will be ‘momentary’. To change
the gain, 48V phantom and talkback switch mode settings: (this proceedure is also detailed in the accessing the
CAL modes chapter)
Press the CAL switch. The switch LED flashes, which indicates you’re now in CAL mode.
Press the TALKBACK switch. Once you do this, the main level/edit LED display will show the current mic amp gain
level in dB and the LCD screen will read ‘set preamp gain’ (screenshot 5)
talkback mic amp gain setting
screenshot 5
To increase the mic amp gain, rotate the main level encoder in a clockwise direction. As you do this, you’ll see
the gain settings change. Preamp gain is adjustable from +10 to +60dB in approximately 3dB steps. Rotate the
encoder in a counter-clockwise direction to reduce the gain level.
If you’d like to change the state of 48V phantom power, press the TALKBACK switch again. The LED display now
shows the on/off state of 48V for the preamp. Rotating the main level encoder to the right turns 48V on and
rotating to the left turns it off. (screenshot 6)
