Getting started

RNPQuickstartV050 Page 10 of 10
FMR Audio, [phone] www.fmraudio.com
provided at this point is over voltage protection to keep transients from unnecessarily stressing the pream-
plifier’s front end.
SOURCE SELECTION — A relay is provided to switch between either the DI (Hi-Z) input or the mic input.
This selection is done by the microprocessor by monitoring the presence/absence of a plug inserted into
the “Hi-Z” jack. When a plug is inserted, the source relay switches to the DI input, otherwise, the mic
input is selected.
PREAMP & GAIN CONTROL — The heart of the RNP is the Class-A, self-biasing preamp stage and its gain
control. The preamp utilizes DC servos to reduce gain control transients and a stepped attenuator (12-posi-
tion) with discrete gain setting resistors. This gain control mechanism ensures repeatable gain settings
with minimum channel-to-channel and unit-to-unit gain variability.
INSERT, MUTE & METERING — After the preamp, a relay provides the ability to mute the preamp output
before hitting the “send” signal available on the INSERT jack (Tip = send, Ring = receive). This same point
is monitored by the microprocessor/metering circuits to display the output level of the preamp.
POLARITY INVERSION — After the INSERT RETURN, a relay provides a polarity inversion mechanism for
the returning signal.
DIFFERENTIAL & BALANCED OUTPUT DRIVER — This servo-balanced output driver permits either differ-
ential or single-ended operation of the RNP’s output. The 1/4” output jack is wired with Tip=in phase,
Ring =out-of-phase relative to the signal present on the INSERT RETURN jack.
OUTPUT SIGNAL OVERVOLTAGE PROTECTION — Both DC isolation and voltage clamps are provided at
the output jack to reduce the chance of damaging the output driver in the presence large DC or transient
voltages.