1–2 Dual Microphone Supply Type 5935 Brüel&Kjær
User Guide
Chapter 1 — Functional Description
Overview
1.1 Overview
The Dual Microphone Supply Type 5935 has two main functions. Firstly, the unit
supplies the necessary power requirements to attached microphone preamplifiers.
Secondly, active circuitry makes it possible to amplify the output of the preamplifi-
ers by up to +55 dB and to apply an A-weighting filter network.
These two functions apply to both channels, which operate entirely independently.
The two channels are however electrically identical, giving excellent phase charac-
teristics and minimal cross-channel differential gain.
These two functions and the two channels are shown schematically in the block
diagram, Fig.1.1. This diagram should also be referred to whilst reading the follow-
ing sections.
1.2 Power Source
In all cases, the source of power for the Type 5395 is single-polarity low-voltage DC.
This source can take several forms:
● Internal rechargeable batteries
● Internal non-rechargeable batteries
● External 12V battery
● External AC/DC converter (8–16V output)
Externally connected supplies are fed to a voltage regulator before being applied
across the internal battery terminals and, via a switch, to the input of the DC/DC
converter. This arrangement means that an external supply can be used to charge
internal rechargeable batteries, if fitted, even when the On/Off switch is off.
Warning: An external supply must never be applied when non-rechargeable batter-
ies are fitted.
The internal batteries feed the DC/DC converter, via the switch. They are protected
by a 1A fuse.
1.3 DC/DC Converter
This is the main element of the power supply section. The incoming stabilized
power from the batteries or external source is converted to a 150kHz signal, trans-
formed into the required voltages and finally rectified and smoothed. The outputs of
the converter are 0V, ±11 V, +24 V and the switchable polarization voltage of 0, 28
or 200V.
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