How do I make a wireless boundary microphone using the MX391?

FAQ #176 Updated February 13, 2017


How do I make a wireless boundary microphone using the MX391?


Building a Wireless Desktop Microphone Using the MX391


  • Prepare the MX391 to connect to a Shure bodypack wireless transmitter.
    • Unplug the microphone from its in-line preamplifier tube.  Set the tube aside, as it is not needed for the wireless application.  However, the preamplifier tube can be used later should the MX391 be needed in a wired configuration. 
    • Cut the factory installed TA4F connector from the cable.  If needed, trim the microphone cable to the desired length.
    • Install a new TA4F connector.  The connector can be obtained from most electronics suppliers (Switchcraft TA4F) or from the Shure parts department (part number WA330).  The Shield (ground) must be connected to both Pin 1 and the metal body of the connector.  To connect to the body, solder a short jumper wire from pin 1 to the connector's internal metal cable grip.  The Red wire (bias voltage) connects to Pin 2, and the Black wire (audio) connects to both Pin 3 and Pin 4.

Note: If the Shure transmitter body pack is metal (and not plastic), a new TA4F connector does NOT need to be installed.

Parts Needed

  • 1 MX391 boundary microphone
  • 1 Shure wireless system with bodypack transmitter (almost all Shure bodypacks use the TA4F connector). 
  • 1 Switchcraft (or equivalent) TA4F Connector (available from the Shure Parts Department - WA330).



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