SMB/EO1 Series
LECTROSONICS, INC.
14
Microphone RF Bypassing
7HENUSEDONAWIRELESSTRANSMITTERTHEMICROPHONE
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
THEMICROPHONETRANSMITTERCOMPATIBILITY)FTHEELECTRET
microphone is not designed properly for use with wire
less 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.
Some mics require RF protection to keep the radio
signal from affecting the capsule, even though the
transmitter input circuitry is already RF bypassed (see
schematic diagram).
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
RF bypass capacitors at the mic capsule. If this is not
possible, or if you are still having problems, capacitors
can be installed on the mic pins inside the TA5F con
nector housing.
Install the capacitors as follows: Use 330 pF ca
pacitors. Capacitors are available from Lectrosonics.
Please specify the part number for the desired lead
style.
,EADEDCAPACITORS 0.
,EADLESSCAPACITORS0.3##0
All Lectrosonics lavaliere mics are already bypassed
and do not need any additional capacitors installed for
proper operation.
Line Level Signals
The normal hookup for line level signals is:
s 3IGNAL(OTTOPIN
s 3IGNAL'NDTOPIN
s 0INJUMPEDTOPIN
This allows signal levels up to 3V RMS to be applied
without limiting.
If more headroom is needed, insert a 20 k resistor in
series with pin 5. Put this resistor inside the TA5F con
nector to minimize noise pickup.
3 WIRE MIC
2 WIRE MIC
CAPSULE
CAPSULE
SHIELD
AUDIO
SHIELD
AUDIO
BIAS
Alternate locations for bypass capacitors
TA5F
CONNECTOR
TA5F
CONNECTOR
Preferred locations for bypass capacitors
