Setting the Correct Gain Structure

You’re now ready to establish the correct gain structure— the key to getting the best performance from the MPL 1204, or from any mixer, for that matter. This is a simple procedure that ensures optimum input and output levels so that no unnecessary noise (caused by too low a signal) or overload distortion (caused by too high a signal) is created. Here’s a step-by-step description of how to do so:

a.With all connections made (as described above) but with the power amplifier and MPL 1204 off, start by setting the power amplifier volume to minimum.

On the MPL 1204, set all channel Trim knobs to their fully counterclockwise (+4) position and turn all channel Level controls fully counterclockwise (to their “∞ ” position). Set all channel EQ and Pan knobs to their center detent “0” positions.

b.Make sure the Mute switch for all channels is set to the out (unmuted) position check that the Meter 1-2 / 3-4 switch (in the main section) is set to its out (1-2) position. This ensures that all channels are routing signal solely to buses 1 and 2 and that the meter will display the bus 1-2 output.

c.If the Main output jacks are connected to a power amplifer and loudspeakers (as described in #2 on page 13), set the Main Level knob to its 2 o’clock “0” position. If the Control Room output jacks are connected to a power amplifer and loudspeakers (as described in #2 on page 13), set the Control Room Level knob to its 2 o’clock “0” position.

d.Set all channel Aux send knobs and both Aux return Level knobs to their fully counterclockwise (“∞ ”) position. Set both Aux return Balance knobs to their center detent “0” positions.

e.Turn on all devices connected to channel line inputs and Aux returns and set their output level controls to unity gain or, if there is no unity gain indicated on their output control, to maximum. If you’ve got outboard effects processors connected to Aux returns, make sure they are sending completely “wet” (processed) signal, with no “dry” (unprocessed) signal mixed in. If condenser microphones are connected to the MPL 1204, turn on the Phantom switch.*

f.Set the bus 1 and bus 2 faders at their “0” (unity gain) position and turn on the MPL 1204’s rear-panel Power switch— the Power LED in the main section will light up. Finally, turn on your power amplifier.

g.Play an instrument connected to one of the MPL 1204’s line inputs** and, while doing so, slowly raise the corresponding channel Level control to the

2 o’clock “0” position. You should see the MPL 1204 meters begin to move. While watching the meters, adjust the Trim control for that channel so that the “0” segment lights frequently, with only occasional excursions into the “+” segments. If the signal seems too hot even with the input channel trim all the way at its minimum (+4) setting, you may need to lower the output level of the instrument, though this will rarely occur. Conversely, if the signal is too low even with the input channel trim all the way up, something's definitely wrong: in all likelihood, the connecting audio cable is faulty.

*CAUTION: Before turning phantom power on, be sure to verify that all connected mic(s) and/or active DI boxes require 48 volts. Also, disconnect all other signal sources (such as passive DI boxes) from the XLR mic jacks.

**If you’re using an instrument such as electric guitar or bass, we recommend that you connect it to the MPL 1204 with a direct injection box to ensure correct impedance.