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Instructions for the DDI-3 DataPort Accessory Card

I. INTRODUCTION

The DDI-3 DataPort Accessory Card converts a QSC amplifier’s DataPort to an eight-position terminal block, providing
convenient access to the pins of the amplifier’s DataPort; this is useful for connecting input signals or implementing a
remote on/off (standby) system without using a DataPort cable. Four solder pads provide access to the amplifier’s output
voltage and current monitors.
QSC ISA, CX, DCA, SRA, PowerLight, and PowerLight 2 Series amplifiers feature a DataPort for every two audio channels.
Therefore, one- and two-channel models have one DataPort, while four-channel models have two and eight-channel models
have four. On the four- and eight-channel CX and DCA models, only the DataPort for channels 1 and 2 has the power supply
standby feature. ISA models do not have power supply standby or output voltage and current monitoring.

ON/OFF CONTROL

A TTL-type logic
low
at DataPort pin 2, such as a short to ground (Figure 2), puts the power supply in
standby. Opening the short will restart the power supply, with no inrush current surge. To control multiple
amplifiers with a single switch, use diodes to isolate them from each other (Figure 3).

INPUTS

Through its DataPort, an amplifier’s input sensitivity (the input voltage required to reach full rated output
power) is approximately 3 volts RMS, at full gain and with an 8Ω load on each channel. Use the + and -
terminals for balanced connections; the AGND terminal is audio ground, for conecting a cable shield when
necessary. For unbalanced connections, connect the signal conductor to the + terminal and the cable shield
to both the AGND and - terminals.

OUTPUT MONITORS

There is a VMON and an IMON output for each amplifier channel. The VMON output is a sample of the
amplifier channel’s output voltage, scaled so that full output into an 8Ω load equals approximately 3 volts
RMS. The IMON output is a voltage proportional to and in phase with the amplifier channel’s output current; the
scaling varies among the various amplifier models; contact QSC for details if you wish to use this feature.
STBY
CGND
CH2+
CH2-
AGND
CH1+
CH1-
AGND
VMN1
IMN1
IMN2
VMN2
STBY
CGND
CH2+
CH2-
AGND
CH1+
CH1-
AGND
VMN1
IMN1
IMN2
VMN2
Run
Standby
STBY
STBY
STBY
CGND
CGND
CGND
CH2+
CH2+
CH2+
CH2-
CH2-
CH2-
AGND
AGND
AGND
CH1+
CH1+
CH1+
CH1-
CH1-
CH1-
AGND
AGND
AGND
VMN1
VMN1
VMN1
IMN1
IMN1
IMN1
IMN2
IMN2
IMN2
VMN2
VMN2
VMN2
Run
Standby
1N914, 1N4148, etc.
Figure 3. On/off control of several
amplfiers with a single switch

II. INSTALLATION

The DDI-3 kit (QSC part # SG-000235-00) includes these items:
DDI-3 board
Two #4-40 × ¼” black screws
Installation guide
Use this procedure to install the DDI-3:
1. Turn off the amplifier.
2. If you are using the output voltage or current monitoring features, solder the wires to the appropriate pads on the DDI-3 before attaching
it to the amplifier.
3. Plug the DDI-3 into the amplifier’s DataPort. Use the two screws included to secure it; do not overtighten them.
4. To attach a wire to the DDI-3, strip about 5 mm (0.2”) of insulation from the wire. Twist the exposed wire strands together and make sure
there are no stray ones. Turn the screw on the terminal counterclockwise until you can fully insert the wire end into the terminal. Turn
the screw clockwise until the terminal clamps the wire securely. Repeat for all the wires needed.
5. The amplifier is ready for use.
Figure 1. The DDI-3
Figure 2. On/off control of a
single amplifier