QSC MD-LP118, User Manual

Page: 5 / 56

5
EN
Input (IN) and
Output (OUT)
Connectors
Filter Select Switch
Gain Control
1= shield (ground)
3= minus (-)
2= plus (+)
1= shield (ground)
3= jumper to pin 1
2= plus (+)
Input/Output Connections
The MD has a balanced 3-pin female XLR input marked IN and a male XLR output connector marked OUT. The
IN and OUT connectors are wired in parallel, enabling connection of multiple enclosures in a “daisy-chain”
fashion.
Balanced connections are recommended for less AC hum and interference, especially with long cable runs.
Unbalanced connections may be suitable for short cables. The signal's source impedance should be less than
600 ohms.
Input connection
Insert the male XLR input into the jack marked IN. Ensure the connector is fully seated. The input impedance is
12k ohm balanced or 6k ohm unbalanced.
Balanced inputs: Connect to the plug as shown.
Unbalanced inputs: Connect to the plug as shown. Pin 3 and pin 1 must be connected with a jumper as
shown.
Output Connection
Insert the female XLR connector into the jack marked OUT. Connect the other end of the cable to the next
down-stream audio device’s input connector.
Gain Control
The Gain control is recessed and can be adjusted with a small screwdriver or flat tool. Turn the gain control
clockwise to increase gain and counter clockwise to decrease gain. The attenuation in dB (from maximum) is
shown on the label.
The Gain control is marked in dB of attenuation. There are 21 detents for repeatable adjustments. The upper 14
steps are about 1 dB each, and settings should normally be made within this range. The range below -14 dB
should not be used for normal program levels, as the input headroom could be exceeded, but can be used for
testing at reduced levels. At the minimum setting, the signal is completely cut off.
Filter Select Switch
Above the Gain control is a small toggle switch that selects either Full Range input or applies a 100 Hz Hi-Cut
filter to the input signal.
100 Hz Hi-Cut Setting (Lo-Pass Setting)
Engages an internal fourth-order crossover filter. It is designed to work with the 100 Hertz Lo-Cut filter on two-
way, powered MD loudspeakers, forming an acoustically matched crossover without external processing.
Full Range Setting
Use the Full Range setting for applications with upstream filtering or signal processing. This allows tailoring of
the sound to your tastes using your signal processing. The input signal must be appropriately processed for the
enclosure (i.e. low frequency signal only). Do not apply a full-range audio input as the internal high-frequency
protection circuit may shut down the amplifier.
Do not apply an input signal with high-frequency content when Full Range is selected!