Lectrosonics M187 - Manual (Page 9)

Belt-Pack Transmitter
M187 INPUT JACK WIRING
The wiring diagrams shown on the attached sheet represent the basic wiring necessary for the most common types of
microphones and other audio inputs. Some microphones may require extra jumpers or a slight variation on the dia­
grams shown.
Caution - When wiring the connector, do not use the connector body for any electrical connections.
A common mistake is to use the connector body as an audio ground. The connector body is
already used as an RF ground and no other use is permitted.
It’s virtually impossible to keep completely up to date on changes that other manufacturers make to their products. It
is possible that you may encounter a microphone that differs from these instructions. If this occurs please call our toll-
free number listed in the back of this instruction manual. Our service department can answer your questions regard­
ing microphone compatibility.
When used on a wireless transmitter, the microphone element is in the proximity of the RF coming from the transmit­
ter. 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 will
be necessary to install a chip capacitor in the mic capsule or connector to block the RF from entering the electret
capsule. These types of modifications are not shown on the attached instructions.
The M187 uses the shield of the microphone cord as the antenna. Other brands use a “dangling wire” to emit the RF
from the transmitter. There is really no difference between these two approaches, with respect to the effect of the RF
on the microphone capsule. Even in transmitters that utilize a “dangling wire,” the microphone is still part of the
“ground plane” and is therefore still in the antenna circuit.
For answers to questions regarding microphone/transmitter compatibility, call our service manager or engineering
department at the factory.
Transmitter
4
3
2
1
5
LECTROSONICS
1uH
10K
1K 5
510
4
3
2
1
60NH
330PF
330PF
+
5V Mic Bias
5mA max
To Mic Amp
POS BIAS (OR GND)
MIC
SOURCE LOAD
LINE IN
NEG GND (OR BIAS)
RF to Antenna
(mic cord)
Input Jack 185/187 Series
Transmitter Equivalent Input Circuit
PIN 1 Shield (ground) for positive biased electret lavalier microphones. Bias voltage source for negative biased
electret lavalier microphones. Shield (ground) for dynamic microphones and line inputs.
PIN 2 Shield (ground) for negative biased electret lavalier microphones. Bias voltage source for positive biased
electret lavalier microphones.
PIN 3 Low impedance microphone level input for dynamic microphones. Also accepts hand-held electret micro­
phones provided the microphone has its own built-in battery.
PIN 4 1K ohm source load for non-Lectrosonics electret microphones. Use in conjunction with other pins to provide
attenuation of high level input signals.
PIN 5 High impedance, line level input for tape decks, mixer outputs, musical instruments, etc.
Rio Rancho, NM – USA 9