Rb-Ma1 Single & Rb-Ma2 Dual Microphone Amplifiers; Introduction; System Block Diagram; Fig 5-1: Rb-Ma1 & Rb-Ma2 Front Panel - Sonifex Redbox RB-SS10 User Handbook Manual

5
MICROPHONE AMPLIFIERS
& LI MI TE R S
5 RB-MA1 Single & RB-MA2 Dual Microphone Amplifiers

Introduction

Fig 5-1: RB-MA1 & RB-MA2 Front Panel.
The RB-MA1 consists of an independent low-noise microphone pre-amplifier for converting
microphone level signals to line level, or for driving long lines from microphones to mixing
equipment. The RB-MA2 dual microphone amplifier consists of two low noise pre amplifiers.
All connections and controls are on the rear panel. The microphone input is XLR-3 type and
is electronically balanced. The input gain can be adjusted individually by a recessed pre-set
potentiometer.
The XLR-3 line output is electronically balanced and can be wired unbalanced by grounding
the non-phase signal, allowing you to feed both balanced and unbalanced equipment.
For each channel there are independent switches to control a high pass filter (low frequency
roll-off at 125Hz) and to provide phantom power at +48V to the connected microphone. An
LED power indicator on the front panel displays the power supply connection.
The rest of this chapter will refer to both RB-MA1 and RB-MA2 unless stated otherwise.

System Block Diagram

Ultra low noise
high gain
amplifier
L.F.
Filter
Balanced
Professional
Microphone
balanced output
Gain
Input
L.F. Filter in/out
Phantom supply on/off
48V
Phantom
power
(48V)
Fig 5-2: RB-MA1 & RB-MA2 Block Diagram Single Channel.
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Redbox User Handbook No 3