1–4 Dual Microphone Supply Type 5935 Brüel&Kjær
User Guide
Chapter 1 — Functional Description
Channel Amplifier and Weighting Filter
1.4 Channel Amplifier and Weighting Filter
The output of an attached microphone preamplifier passes through an amplifier
stage before being sent either to the A-weighting filter or directly to the output
sockets. This amplifier stage, identical for each channel, has a high input imped-
ance and a very low output impedance, ideal for buffering microphone preamplifi-
ers, particularly when long microphone cables are used.
The amplifiers have switchable gain from 0dB to 50dB in 10dB steps. There is
also a front-panel screwdriver adjustment which has a range of ±5dB. This ar-
rangement, together with the switched gain stage, allows you to set up the opti-
mum input level for the next piece of equipment in the signal chain. The front-
panel screwdriver adjustment is fine enough to exactly balance the output of two
microphone preamplifiers when precise level matching is needed.
An overload detector is fed from each channel to warn when the signal passing
through the unit is approaching maximum level.
An active A-weighting filter comes after the amplifier stage. This filter has IEC
Type 0 characteristics.
The Lin. (un-weighted) outputs of the channels are closely phase matched.
1.5 Output Sockets
There are two output sockets on the front panel and four on the rear panel. The
signals appearing on these sockets come from different parts of the active circuitry
and are a combination of un-weighted signals and A-weighted signals, either AC- or
DC- coupled.
The front panel sockets are AC-coupled and are fed either with the un-weighted
amplifier signal or the A-weighted signal, depending upon the position of the A/Lin.
switch. Furthermore, there is a switch arrangement to allow the sockets to swap
channels, so that, for example, channel 1’s output appears on channel 2’s front-
panel output socket.
The LIN and A-weighted output sockets on the rear panel are DC coupled, and
cannot be swapped.
To Next Page
Loading...
