Getting started

RNPQuickstartV050 Page 9 of 10
FMR Audio, [phone] www.fmraudio.com
S IGNAL F LOW
Referring to Figure 3, the signal flow for the RNP is as follows:
MIC INPUT — The XLR female connector accepts standard mic cable from a microphone. The polarity on
this connector follows current convention of pin#1 is reference, pin#2 is hot, and pin#3 is cold. The differ-
ential-mode impedance is approximately 5k Ω .
PHANTOM RESISTORS — These two 6.81k Ω /1W resistors provide current to an attached condenser micro-
phone from a 2W, 48V low impedance driver. When phantom is not engaged, these two resistors are dis-
connected from the 48V driver and are “seen” by the microphone as a 13.6k Ω differential-mode
impedance.
EMI & OVERVOLTAGE PROTECTION — A third order, passive filter is provided between the mic input and
the preamplifier stage to reduce RFI/EMI interference (cutoff frequency is approximately 240kHz). Also
Figure 3: RNP Block Diagram
EMI &
Over-V
Protection
Ø
Over-V
Protection
±18V
+50V
Logic
EMI, Over-V
& Polarity
Protection
+48V
Driver
CPU
&
Signal
Conditioners
Channel 1 (Ch. 2 is identical)
+
-
Meter & Switches
"HiZ Input"
"Mic Input"
"Source"
"Invert""Mute"
"Output"
"Insert"
(Tip = Send, Ring = Return)
(Tip = +, Ring = -)
"+48V Engage"
Switch &
Resistors
"Gain"
"Power"
Preamp/
Servos
01/09/02 Rev. --