BRUEL & KJAER 2672, Руководство пользователя

Страница: 8 / 32

Chapter 1 — Introduction
About Type 2672
Sound Quality Conditioning Amplifier Type 2672
User Manual
Brüel & Kjær
1
−
2
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 4100 D.