PS Engineering
PMA8000-SR Series Audio Selector Panel and Intercom System
Installation and Operator’s Manual
200-880-0000
Page
2-3
Rev. 14, Oct. 2008
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.
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 Existing GMA340 Installation
In order to replace the GMA340 with a PMA8000SR, the unit tray must be removed and replaced with the
new PMA8000 tray. The connectors can be reused. You will have to replace the back plate (430-880-0050)
and connect the Satellite Radio antenna to the RF connector (425-880-3003).
2.4.2.1 J2, Pin 30 GMA340
Some GMA340 installations may have a ground strap on J2, Pin 30, Com TX mute.”
THIS
CONNECTION MUST BE REMOVED.
If the PMA8000 installation is routing the SIRIUS Satellite Radio audio externally, this pin is reused as
Satellite Radio Audio Right channel. If the Satellite Radio remains internal, this pin must be disconnected.
2.4.3 Power
The PMA8000-SR-Series are compatible with both 14 and 28 Volt DC systems. A five (5) Amp circuit
breaker is required for all installations. Power and ground wires must be a twisted #22 AWG pair con-
nected to J2 Pins 8 and 9. Connect airframe ground to J2 Pin 10 and 11 only. No dropping resistors are
required.
2.4.4 Communications Push-to-Talk
An important part of the installation is the PTT (Push-To-Talk) switches that allow the use of your aircraft
communications radio for transmissions. There are three typical configurations that can be used. Select the
case that best fits the installation. Only the person who presses their PTT switch will be heard over the ra-
dio. If the pilot and copilot both use the PTT, the only pilot position has access to the radio. The pilot posi-
tion will have PTT control regardless of the mic selector switch or copilot PTT when the PMA8000-SR is
in the
OFF
/E
MG
mode.
CASE I
: PTT is built into both pilot and copilot yokes.
CASE II:
PTT is in pilot yoke only. This configuration requires a modified external PTT switch plugged
into the copilot's microphone jack. (See Appendix A). When the copilot's PTT is pressed, the intercom
switches the microphone audio from pilot to copilot mic.
CASE III
: No built in PTT. This requires two built in PTTs to be installed, or modified external PTT
switches to be used. Modify external PTT as required. See Appendix A.
2.4.5 Audio Panel interface
The PMA8000-SR is designed to interface with standard aircraft avionics, and presents a 500
Ω
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.
2.4.5.1 Speaker Load
The PMA8000-SR 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.