PS Engineering PMA6000B - Manual (Page 9)

PS Engineering
PMA6000B Audio Selector Panel and Intercom System
Installation Manual
200-066-0200 Page 2-3 Rev 6, Feb. 2013
2.4.1 Noise
Due to the variety and the high power of radio equipment often found in today's general aviation aircraft,
there is a potential for both radiated and conducted noise interference.
The PMA6000B power supply is specifically designed to reduce conducted electrical noise on the aircraft
power bus by at least 50dB. Although this is a large amount of attenuation, it may not eliminate all noise,
particularly if the amplitude of noise is very high. There must be at least 13.8 VDC present at the bottom
connector, pin 43, of the PMA6000B for the power supply to work in its designed regulation. Otherwise, it
cannot adequately attenuate power line noise. Shielding can reduce or prevent radiated noise (i.e., beacon,
electric gyros, switching power supplies, etc.) However, installation combinations can occur where inter-
ference is possible. The PMA6000B is designed in a RFI hardened chassis and has internal Electromag-
netic Interference (EMI) filters on all inputs and outputs.
Ground loop noise occurs when there are two or more ground paths for the same signal (i.e., airframe and
ground return wire). Large cyclic loads such as strobes, inverters, etc., can inject noise signals onto the
airframe that are detected by the audio system. Follow the wiring diagram very carefully to help ensure a
minimum of ground loop potential. Use only Mil Spec shielded wires (MIL-C-275000, or better). Under
no circumstances combine a microphone and headphone wiring into the same shielded bundle. Always
use a 2- or 3-conductor, shield wire as shown on the installation wiring diagram.
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.
Adding a high-performance audio control system, particularly in conjunction with 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 installation condi-
tions, particularly with older avionics.
2.4.2 Entertainment Input
Two entertainment devices (MP3 player, Portable Satellite Radio, CD player, etc.) can be connected to the
unit. Install two 1/8-inch jacks in a convenient location so that the pilot can plug in the entertainment
devices into the system.
NO T E : Use t h e l ow l evel ou t p u t of a n y en t er t a i n m en t d evi ce t o con n ect t o t h e
a u d i o p a n el . Ma x i m u m si g n a l l evel i s 2 VAC p - p . DO NO T u se a sp ea k er - l evel
ou t p u t , t h i s wi l l ca u se i n t er n a l d a m a g e i n t h e a u d i o p a n el .
T o u se a l i n e l evel , i n st a l l a Scosch e SLC 4 , P/ N 1 4 2 SLC 4 a d a p t er , a va i l a bl e
fr om C r u t ch fi el d a t 1 - 8 0 0 - 9 5 5 - 3 0 0 0
sa l es@ cr u t ch fi el d . com
For a stereo input, we do not recommended tying the left and right channels (tip and ring) together unless
approved by the music source manufacturer. The audio signal at the entertainment input must be a mini-
mum of 500 mV P-P for optimum music performance.
2.4.2.1 Soft Mute
The PMA6000B-system incorporates a "Soft Mute" system. This will mute the entertainment devices dur-
ing ICS or radio traffic. While in the ALL or ISO modes, entertainment #1 is heard by everyone (except
by the pilot in ISO mode). While in the CREW mode, pilot and copilot will hear entertainment #1 while
the passengers will hear entertainment #2.