Lectrosonics LM User Manual download pdf (Page 10)

LM/IM

5-Pin Input Jack Wiring

Note: This section does not apply to the IM

transmitter when used as part of the IS400

Instrument System. The cable supplied with the

IS400 Insturment System is prewired and cannot

be field modified. The cable is available in two

configurations, MI33ARA (right angle) and

MI33AST (straight).

The wiring diagrams shown in Wiring Hookups For

Different Sources represent the basic wiring configura-

tions necessary for the most common types of micro-

phones and other audio inputs. Some microphones

may require extra jumpers or a slight variation in the

diagrams shown.

It’s virtually impossible to keep completely up to date on

changes that other manufacturers make to their prod-

ucts. It is possible that you may encounter a micro-

phone that differs from those illustrated. If this occurs

please visit our website and select the

Mic Wiring Info

quick link, or call our toll-free number listed in the back

of this manual for assistance.

When used on a wireless transmitter, the microphone

element is in the proximity of the RF coming from the

transmitter. The nature of electret microphones makes

them sensitive to RF, which can cause problems with

the microphone/transmitter compatibility. If the electret

microphone is not designed properly for use with

wireless transmitters, it may be necessary to install a

chip capacitor in the mic capsule or connector to block

the RF from entering the electret capsule. (See RF

Bypassing.) Obviously, RF bypassing is not a problem

when using the IM transmitter with the IS400 Instru-

ment System.

PIN 1 - Shield (ground) for

positive biased electret lavalliere

LECTROSONICS

microphones. For the increas-

ingly rare negative biased

electret lavalliere microphones, it

is the bias voltage source. It is

also the shield (ground) for

dynamic microphones and line

level inputs.

TRANSMITTER

PIN 2 - Shield (ground) for

INPUT JACK

negative biased electret lavaliere

microphones. Bias voltage

source for positive biased electret lavaliere micro-

phones.

PIN 3 - Low impedance microphone level input for

dynamic microphones. Also accepts hand-held

electret microphones that have their own battery or

power supply.

PIN 4 - 4 k Ohm source load for non-Lectrosonics

electret microphones. Use in conjunction with other

pins to provide attenuation of high level input

signals.

PIN 5 - 40 k high impedance, line level input for

tape decks, mixer outputs, musical instruments, etc.

Input Circuit

RF Bypassing

Some mics require RF protection to keep the transmit-

ter signal from affecting the capsule, even though the

transmitter input circuitry is already RF bypassed (see

5-Pin Input Jack Wiring schematic diagram above).

If the mic is wired as directed, and you are having

difficulty with squealing, high noise, or poor frequency

response, RF is likely to be the cause.

The best RF protection is accomplished by installing

330 pF bypass capacitors at the mic capsule. If this is

not possible, or if you are still having problems, capaci-

tors can be installed on the mic wires inside the TA5F

connector housing.

The 330 pF capacitors are available from Lectrosonics.

Please specify the part number for the desired lead

style.

Leaded capacitors: P/N 15117

Leadless capacitors: P/N SCC330P

Note: The Lectrosonics M150 lavaliere mic is

already bypassed correctly for use with the LM or

IM transmitters.

2 WIRE MIC 3 WIRE MIC

CAPSULE

CONNECTOR

Alternate locations for bypass capacitors

TA 5F

CONNECTOR

CAPSULE

SHIELD

AUDIO

SHIELD

AUDIO

BIAS

TA5F

Preferred locations for bypass capacitors

LECTROSONICS, INC. 10

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