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I have many UM400 and UM400a transmitters on a reality show. I'm coming out all my mixers at mic level into either the UM400 or the UM400a transmitters using a MC40 cable. The gain settings are confusing. What can I do to make this easier?


The mic level input on the UM400a has the new servo input with much more gain for low impedance signals than the UM400 with the older input. The increased gain improves performance with dynamic microphones. However, switching back and forth between the UM400 and UM400a transmitters will require constant readjustment of the gain setting if you are using the MC40 cable. To make life simpler we have a MC41 cable that will work with either transmitter type and matches the gain to within a few decibels. If you want to build your own, the wiring of the TA5F is as follows:

  • pin 1 is ground
  • pin 2 N/C
  • pin 3 to a 3k resistor in series with the mic level wire.
  • pin 4 jumped to pin 1 (sets the servo bias to zero)
  • pin 5 N/C

This places resistance in the audio line and reduces the input to the UM400 by only a few decibels but reduces the UM400a by 20 dB and matches them very closely. The MC41 can be used with all the servo bias mics such as the SMa, SMQa, SMDa, UM400a, UM450, and LMa. It will also work well with any of the older style transmitters.

Posted 1 year agoby LectroAdmin