PS Engineering PMA8000D Installation Manual - Manual (Page 11)

PS Engineering
PMA8000D Audio Selector Panel and Intercom System
Installation and Operator’s Manual
200-890-0304 Page 2-3 Rev. 6, Oct. 2014
The shields can be daisy-chained together, and then connected to the ground lugs mounted on the back plate
shown in Appendix B.
Radiated signals can be a factor when low level microphone signals are "bundled" with current carrying
power wires. Keep these cables physically separated. It is very important that you use insulated washers to
isolate the ground return path from the airframe to all headphone and microphone jacks.
2.4.1.1 Music Inputs and Noise
PMA8000D units utilize a differential input to help prevent noise from entering the music system. This fea-
ture is usually transparent to the installer; however, it is important that the appropriate music signal and
ground connections are made directly to the dedicated music signal and ground inputs on the PMA8000D.
The power for IFE and audio panel should be a common bus.
If a music jack instead of a music source is installed for Music 1 or 2, we recommend grounding the jack to
airframe ground.
NOTE
Adding a high-performance audio control system, particularly in conjunction with high-performance active
noise canceling headsets, cannot improve on older avionics that were designed for cabin-speaker use. PS
Engineering makes no claim that the audio panel will provide a noise-free audio quality under all installa-
tion conditions, particularly with older avionics.
2.4.2 Power
The PMA8000D is compatible with both 14 and 28 Volt DC systems. A five (5) Amp circuit breaker is
required for all installations. Power and ground wires should be #22 connected to J2 Pins 8 and 9 on each
audio panel. Connect airframe ground to J2 Pin 10 and 11 only, in each audio panel. No dropping resistors
are required.
2.4.3 Audio Panel interface
The PMA8000D is designed to interface with standard aircraft avionics, with a 510
 receiver impedance.
For best results, a twisted-shielded cable is recommended from the avionics audio source to the audio panel,
with the shield grounded at the audio panel end.
Some avionics do not provide a separate audio low, and may introduce additional electrical noise into the
system. For best results, connect the audio low from the audio panel to the radio ground, using one conduc-
tor of the twisted-shielded cable.
2.4.4 Cockpit Speaker
Each PMA8000D contains a cockpit speaker amplifier. Any radio audio source will be presented to the
cockpit speaker when the SPR button is selected.
NOTE: Do NOT connect both audio panels directly to a single cockpit speaker. This could damage
the audio panel. A dedicated cockpit speaker is recommended for each audio panel.
2.4.4.1 Speaker Load
The PMA8000D contains one speaker amplifier. Some units with internal speaker amplifiers, such as the
King Radio KX170-series, require a resistive load to prevent damage if their speaker amplifier is not used.
Connect the speaker output from the unit to the COM 2 Speaker load input on the PMA8000D (J1 27 WRT
28). The speaker load is 16
, 3W. Only one speaker per load is available in the PMA8000D.
2.4.5 Backlighting
The PMA8000D has an automatic dimming of the pushbutton green annunciation LEDs and marker lamps
controlled by a photocell. Control of the unit white backlighting is through the aircraft avionics dimmer. For
14 V (or 5 VDC p/n 050-890-0304, only) aircraft, connect J2 Pins 6 and 7 to the aircraft dimmer bus, and
pin 5 to ground. For 28-volt systems, connect pin 7 to the aircraft dimmer, and pins 5 and 6 to ground.