BRUEL & KJAER 2672 User manual

Technical
Documenation t
Brüel&Kjær
BK
7/6-'89
BE1461–11
Sound Quality Conditioning Amplifier
Type 2672
User Manual

September 1995
BE1461–11
Brüel & Kjær Sound Quality Conditioning Amplifier Type 2672
User Manual
Sound Quality Conditioning Amplifier
Type 2672

0−2Brüel & KjærSound Quality Conditioning Amplifier Type 2672
User Manual
Safety Considerations
This apparatus has been designed and tested according to IEC Publication 1010–1,
Safety Requirements for Electronic Equipment for Measurement, Control and Labora-
tory Use, and has been supplied in safe condition. The User Manual contains infor-
mation and warnings which should be followed by the user to ensure safe operation
and to retain the apparatus in safe condition. Special note should be made of the
following:
Safety Symbols
The apparatus will be marked with this symbol when it is important that the
user refers to the associated warning statements given in the User Manual
Frame/Chassis terminal Protective conductor terminal Hazardous voltage
Explosion Hazard
The amplifier is not designed to be used in potentially explosive environments. It
should not be operated in the presence of flammable liquids or gases.
Warnings
• Whenever it is likely that the correct function or operating safety of the apparatus has
been impaired, the apparatus must be made inoperative and be secured against unin-
tended operation.
• Any adjustment maintenance and repair of the open apparatus under voltage must be
avoided as far as possible and, if unavoidable, must only be made by trained service
personnel.
!
Copyright © 1995, Brüel&Kjær A/S
All rights reserved. No part of this publication may be reproduced or distributed in
any form or by any means without prior consent in writing from Brüel & Kjær A/S,
Nærum, Denmark.

Sound Quality Conditioning Amplifier Type 2672
User Manual
BE1461–11 0−3
Contents
1. Introduction....................................................................................................................... 1–1
1.1 About Type 2672.......................................................................................................... 1–2
1.2 About this Manual....................................................................................................... 1–3
2. Controls and Connectors........................................................................................ 2–1
2.1 Front Panel.................................................................................................................. 2–2
Filters...................................................................................................................... 2–2
Gain......................................................................................................................... 2–2
Input........................................................................................................................ 2–3
Output..................................................................................................................... 2–4
2.2 Back Panel................................................................................................................... 2–4
Battery .................................................................................................................... 2–4
Power....................................................................................................................... 2–4
3. Preliminary........................................................................................................................ 3–1
3.1 Environmental............................................................................................................. 3–2
Temperature ........................................................................................................... 3–2
Electromagnetic Compatibility.............................................................................. 3–2
3.2 Power Supply............................................................................................................... 3–2
Internal Battery...................................................................................................... 3–2
External Power Supply .......................................................................................... 3–2
Fuse......................................................................................................................... 3–3
4. Using Type 2672............................................................................................................ 4–1
4.1 Use with a DAT Recorder ........................................................................................... 4–2
Combined System................................................................................................... 4–2
Assembling the System .......................................................................................... 4–2
4.2 Use with Positioning Frame UA 1324 ........................................................................ 4–2
4.3 Selection of Input ........................................................................................................ 4–3
4.4 Charge-injection Calibration ...................................................................................... 4–3
Brüel & Kjær’s Patented Charge-injection Calibration Technique...................... 4–3
CIC using Type 2672 .............................................................................................. 4–4
4.5 Gain.............................................................................................................................. 4–4
High/Low................................................................................................................. 4–4
Overload.................................................................................................................. 4–5

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Contents
4.6 Filters........................................................................................................................... 4–5
High-pass................................................................................................................ 4–5
DFCF....................................................................................................................... 4–5
4.7 Output.......................................................................................................................... 4–6
5. Specifications................................................................................................................... 5–1
6. Service & Repair........................................................................................................... 6–1
Index

Sound Quality Conditioning Amplifier Type 2672
User Manual
BE1461–11 1−1
Chapter 1
Introduction

Chapter 1 — Introduction
About Type 2672
Sound Quality Conditioning Amplifier Type 2672
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1.1 About Type 2672
The Amplifier
Sound Quality Conditioning Amplifier Type 2672 is a dual-channel conditioning
amplifier for use with Sound Quality Head and Torso Simulator Type 4100 or
4100 D. The amplifier has preamplifier inputs for use with Preamplifier Type 2669
(4100), and a selectable Direct/CCLD input for use with direct (electrical) signals or
with DeltaTron®Preamplifier Type 2671 (4100 D). When using Type 2669, charge
injection calibration (CIC) is available for rapid calibration of your sound quality
system.
The amplifier takes analogue signals from the microphones and other sources and
conditions these for recording on a DAT recorder, analyzer, etc. The amplifier’s au-
dio channels operate entirely independently, with separate gain, filters and input
selectors. In terms of noise and distortion, the active circuitry conforms to the same
high specification expected of digital audio systems.
Diffuse Field Correction Filter
Head and torso simulators are normally calibrated in a diffuse field, but the diffuse-
field frequency response of the simulator is far from flat and needs to be normal-
ised. This can be achieved in the conditioning amplifier which has a selectable
Diffuse Field Correction Filter that is matched to diffuse-field characteristics of
Sound Quality Head and Torso Simulator Type 4100 (D)*. Filtering the signals be-
fore they are processed and recorded improves the signal-to-noise ratio by up to
10 dB in the frequency range 2 – 6 kHz.
CIC
Charge Injection Calibration is a technique which allows you to get a very precise
indication of the correct functionality of the microphone, preamplifier and extension
cables. Injecting a signal at the junction between the microphone capsule and
preamplifier lets you measure any changes in leakage capacitance. If there is no
change compared to a previous measurement, you can rely on the system being in
perfect condition – and any acoustic calibration done earlier with, for example, a
pistonphone will still be correct.
Use with a DAT Recorder
To make it easy to use Type 2672 with a SONY PC 204 A DAT recorder, the condi-
tioning amplifier has the same case size as the recorder. The two instruments then
fit neatly into Guard Frame WU 0484 to form a compact, battery-operated unit.
Both units use the same type of rechargeable battery or external power source,
avoiding the need for different power systems. When assembled, both instruments
*Note: 4100(D) means Type 4100 and/or Type 4100D.

Chapter 1 — Introduction
About this Manual
Sound Quality Conditioning Amplifier Type 2672
User Manual
BE1461–11 1−3
fit conveniently into the base of Positioning Frame UA 1324. Type 2672 will, howev-
er, operate efficiently with any type of DAT recorder which has an analogue input.
Sound Quality Recording
Sound Quality Conditioning Amplifier Type 2672 can be combined with:
●Sound Quality Head and Torso Simulator Type 4100 or 4100 D
●Positioning Frame UA 1324
●SONY PC 204 A Instrumentation Cassette Recorder (WQ 1121), or other make of
DAT recorder with analogue input
to form a complete sound quality recording system. These can be assembled as a
single unit which can be placed in the seat of, for example, a car or aeroplane – no
seat modifications are necessary. See the separate Product Data for Type 4100 (D)
and UA 1324 for details.
1.2 About this Manual
Chapter 2 of this manual describes the switches, connectors, etc. found on the front
and back panels of the amplifier. Once you are familiar with Type 2672, you can
use this chapter as a quick reference guide.
Chapter 3 gives details of environmental considerations and describes the use of
batteries and external power supply.
Chapter 4 describes how Type 2672 can be used in a sound quality system and
gives details about using the amplifier.
Chapter 5 contains the amplifier’s specifications.
Chapter 6 gives brief service information.
The manual concludes with an index.

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Sound Quality Conditioning Amplifier Type 2672
User Manual
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Chapter 2
Controls and Connectors

Chapter 2 — Controls and Connectors
Front Panel
Sound Quality Conditioning Amplifier Type 2672
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2.1 Front Panel
2.1.1 Filters
2.1.2 Gain
Fig.2.1 Front panel of Type 2672
Power On: LED lights when the amplifier is switched on.
Batt. Low: LED lights when the battery power is low.
HP: Two 3-position sliding switches for selection of 0.3,10 or 20 Hz
2nd order high-pass filter for left- and right-hand channels.
DFCF: Two 2-position switches for turning the left- and right-hand Dif-
fuse Field Correction Filters On or Off.
On: The filters compensate for the diffuse-field characteristics of
Head and Torso Simulator Type 4100 (D), and give a flat
frequency response.
Off: No compensation is made.
Low/High: Two 2-position switches that you use in conjunction with the
switches to their right for selecting low or high gain adjustment of
the input signals. Settings are:
Low: – 20,–10,0,10 dB
High: 20,30,40,50 dB
Ovld.: Two overload indicators. An LED is lit when there is an overload
in the corresponding channel.
±3dB: Two potentiometers for sensitivity adjustment with a range of
±3 dB relative to the Low/High settings.

Chapter 2 — Controls and Connectors
Front Panel
Sound Quality Conditioning Amplifier Type 2672
User Manual
BE1461–11 2−3
2.1.3 Input
Select: Two 3-position sliding switches for selection of:
Pre.: Preamplifier input via Preamp. connector.
Dir.: Direct input via Dir./CCLD connector.
CCLD:Constant current line drive input via Dir./CCLD connec-
tors for use with DeltaTron®preamplifiers.
Preamp.: Two 7-pin LEMO connectors for input of preamplifier signals
from, for example, Head and Torso Simulator Type 4100. The con-
nectors also provide the microphone polarization voltage and
charge injection calibration signal. Pin designations are given in
Fig.2.2.
Pin
1 Calibration output
2 Signal ground
3 Pol. voltage
4 Signal Input
5 Not connected
6 Power supply positive
7 Power supply negative/ground
Casing Connected to instrument chassis
Fig.2.2 Pin designations for 7-pin LEMO
Preamp. connector (external view)
Dir./CCLD: Two BNC connectors for input of direct (electrical) signals, or sig-
nals from DeltaTron®preamplifiers as used, for example, with
Head and Torso Simulator Type 4100 D. The connector provides a
constant current of 4 mA. The function of the connector is deter-
mined by the position of the Setting switch.
Pol. Voltage: 3-position sliding switch for selection of 0,28 or 200 V microphone
polarization voltage.
Note: The same polarization voltage is applied to both left- and
right-hand channels.
CIC: 4-position sliding switch for selection of the signal to use for
charge-injection calibration (CIC) of Head and Torso Simulator
Type 4100. The signal is applied to both Preamp. inputs (see
Fig.2.2). Settings are:
16
2
34
75

Chapter 2 — Controls and Connectors
Back Panel
Sound Quality Conditioning Amplifier Type 2672
User Manual Brüel & Kjær
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2.1.4 Output
2.2 Back Panel
2.2.1 Battery
2.2.2 Power
Off: No CIC signal.
Ext.: This allows input of a CIC signal from an external genera-
tor. The signal is input via CIC Ext. (see below).
40: A 40 Hz CIC signal is supplied by the amplifier’s internal
generator.
1k: A 1 kHz CIC signal is supplied by the amplifier’s internal
generator.
CIC Ext.: BNC connector for input of CIC signal from an external generator.
Two BNC connectors for output of the conditioned signals to, for
example, a DAT recorder. The output is electronically semi-bal-
anced.
Fig.2.3 Back panel of Type 2672
Compartment: The battery compartment accepts one SONY NP–1B rechargeable
battery (Brüel & Kjær order no. WQ 1129).
Battery release: Releases the battery pack for replacing the battery.
On: Power on/off switch.
Fuse: 2 A fuse for protection of Type 2672 when using an external power
supply.

Chapter 2 — Controls and Connectors
Back Panel
Sound Quality Conditioning Amplifier Type 2672
User Manual
BE1461–11 2−5
Ext. 12 – 20 V DC: 2-pin connection for use with 12 – 20 V, 400 mA external power
supply. Pin designations are given in Fig.2.4.
Fig.2.4 Pin designations for external power
connector (external view)
950743e
Negative Positive
(12 V to
20 V DC)

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Sound Quality Conditioning Amplifier Type 2672
User Manual
BE1461–11 3−1
Chapter 3
Preliminary

Chapter 3 — Preliminary
Environmental
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3.1 Environmental
3.1.1 Temperature
Sound Quality Conditioning Amplifier Type 2672 will work reliably at temperatures
from 0 to +50°C (+32 to 122°F) in a relative humidity of up to 90% non-condensing
at +40°C (+104°F). The safe temperature range for storage is –25 to +70°C (–13 to
+158°F).
3.1.2 Electromagnetic Compatibility
The CE mark indicates compliance with the EMC Directive and the Low Voltage
Directive. See the table in Chapter 5 for full details of compliance to EMC stand-
ards.
3.2 Power Supply
There are three main sources of power for Type 2672:
●Internal rechargeable battery
●External 12 V battery
●External mains AC/DC transformer (12 – 20 V DC supply)
3.2.1 Internal Battery
Type 2672 uses one SONY NP–1B battery (Brüel & Kjær order no. WQ 1129). When
fully charged it gives approximately 5 hours of continuous operation.
When an external 18 – 20 V DC supply (e.g. WB 1375 a or WB 1376 a) is connected
to the amplifier, the internal battery is slowly recharged over a period of 14 hours.
When the internal battery needs recharging, the Batt. Low LED on the front panel
of the amplifier lights.
3.2.2 External Power Supply
Any external supply connected to Type 2672 must supply 12 – 20 V DC and be
capable of supplying 400 mA. This can be achieved using, for example:
●Brüel & Kjær Mains Adaptor WB 1375 a (100 to 127 V AC) or WB 1376 a (200 to
240 V AC)
●12 V car battery (useful when making sound quality recordings in a moving
vehicle)
●Variable DC power supply

Chapter 3 — Preliminary
Power Supply
Sound Quality Conditioning Amplifier Type 2672
User Manual
BE1461–11 3−3
In all cases, the power is supplied via the 2-pin Ext. 12 – 20 V DC connector on the
back panel of the amplifier (see Fig.2.4).
Note: If you want to use an external supply other than WB 1375 a or WB 1376 a,
you will need Cable WL 1192.
3.2.3 Fuse
Type 2672 has a T 2 A fuse (Brüel & Kjær order no. VF 0010) to protect it when
using an external power supply. You can remove the fuse using a small screwdriver
or a coin (Fig.2.3).

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