Microphone Preamplifier0 pages

Product Data

MNorsonic

MICROPHONE PREAMPLIFIER

type 1201

Uses:

• Precision sound measure-

ments using precision

microphone cartridges with

UNS 60 threads

• General purpose high imped-

ance input stage for measur-

ing amplifiers and analysers

Features:

• Small compact design

• Detachable preamplifier

cable

• One-size connector system

eliminates extension cable

incompatibility

• Very high input impedance

• Low output impedance

• Excellent driving capabilities

for long cables

• Wide dynamic range

The microphone preamplifier type

1201 has been designed for

general use with most W condens-

er microphones—with or without

permanent polarisation. Using

mechanical adaptors, the preampli-

fier is well suited for other micro-

phone sizes as well.

The amplifier has a high dynamic

range to permit a large voltage

swing and low noise. A broad

frequency response lets you take

full advantage of the capabilities of

the microphone.

The frequency response covers

a range from below 1 Hz to above

200kHz. The capacitive influence of

the various cartridges and cables

has been minimised by the high

input/low output impedance design.

A push-pull output circuit ensures

good driver capabilities.

The amplifier is equipped with a

heater resistor to increase the

temperature of the microphone/

preamplifier assembly to minimise

the risk of condensation under

humid conditions.

Introduction

The preamplifier type 1201 has been

designed to match the needs of

Norsonic Vz" microphone cartridges,

but may be used as a general pur-

pose input stage for measuring

amplifiers and analysers.

The signal cable is detachable and

the same type and size of connector

is used throughout the cabling system

to ensure extension cable compatibili-

ty. There is no need to use a separate

cable to connect the preamplifier to

an extension cable.

The 1201 has a high input imped-

ance and a low output impedance

combined with excellent driver

capabilities. This design ensures that

the preamplifier presents virtually no

load to the microphone cartridge and

that long cables can be used without

severe signal distortion.

Frequency Response

The small signal frequency responses

of the amplifier are shown in Fig. 1

(overleaf) for different source capaci-

tances. The 18pF corresponds to

most W cartridges and 50pF to most

1" cartridges, while the 6.4pF will be

typical for W size microphones.

The graphs apply when the polari-

sation voltage is on or the polarisation

voltage is grounded in the case of

prepolarised (electret) microphone

cartridges.

Connecting the polarisation voltage

terminal to the output of the 1201,

increases input impedances thereby

improving the low-frequency response

for certain applications.

The frequency response must then

be checked for low-frequency reso-

nances by testing it out with real

source impedances.

The input impedance of most

sound level meters and analysers will

be high enough not to influence the

frequency response of the preamplifi-

er. Long extension cables have a

capacitance that may limit the slew

rate of the output signal. This will

reduce the upper frequency response

for signals with large voltage swings.

Such limiting will be a non-linear

process and may therefore also

disturb the low frequency contents of

the signal. Cable effects should

PD 1201 Ed. 2 Rev 0 ENGLISH 2.95