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MKH50 / UMP-II / UM400 = Buzz. mp3 inside


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Hey Everybody,


Here's a sound clip of the issue - https://drive.google.com/file/d/1j72Oz6bbUYmnHS7TAKu_d5GZF0hkJJxP/view?usp=sharing


I'm using a UMP-II with a UM400 transmitter and a MKH50. I'm getting a "boiling" or buzzing sound from the mic.


My 416 works fine with this exact same set-up. 


I've connect the MKH50 to the UMP-II and then directly to my recorder and it sounds fine. 


I've tried putting a longer xlr between the MKH50 and the UMP-II and the problem remains. 


I've also tried a 200 series and G3 tx and the problem continued. I don't currently have another newer transmitter to test with but the previous owner said the unit worked fine with his MKH50 and SM and 400a transmitters.


I bought the MKH50 new two years old and the only issue I've had with it previously was some faint RF that was fixed by tightening the hex screws. 


Any insight would be appreciated. Maybe they're not compatible or it's possible I'm missing something. Thanks!

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Hi Jimmy,

My guess is that the supersonic switching supplies in the MKH50, UMP-ll, and the UM400a are beating together and causing a difference frequency in the audible range. However, that normally appears as a low level whine.

Here is the link to Ambient that shows the correct cable wiring to convert the balanced floating mic to a grounded unbalanced input on the UM400a:




Pins 1 and 4 should be connected together in the 5 pin TA5F with the blue signal wire tied to pin 1 and 4 and with the red signal wire tied to pin 3 of the TA5F.

Ambient shows the shield tied to ground only at the UMP-ll. This normally is the best wiring with a floating balanced output. If the shield is tied to ground at both ends you can get hum loops. If the TA5F is wired according to Ambient's schematic, as an experiment you can defloat (there's a good word) the system and tie the shield to the ground pins at both ends.


Since I've had no experience with a setup like yours I am merely giving my best guesses.

Best Regards,

Larry Fisher

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Thanks for stepping in Larry.


Here's what Ambient sent to me (I was the previous owner of the UMP)


From Ambient -

...all the interaction between a beltpack, built around unbalanced mid impedant lav mics and a condenser mic, low impedant and balanced can be challenging to find the right configuration. Most part of it is the beltback ground/chassis being part of the RF stage (ground plane the RF signal is generated against). So, the condenser and UMP effectively become port of the “antenna”.


We try to keep options open as much as possible by a) not tying the UMP shell to ground on both ends and b) not supplying the lead for the transmitter.


Things to try:

  • Reverse the phase on the output cable, which means tying hot to ground instead cold
  • Leave ground open (using only pin 3) and connecting shild just on one side (either may give different results)#
  • Cut the wire connecting shell to pin 1 on the TA 4 F connector of the input cable

I’m afraid there is no way around an in depth trial and error procedure to find the optimum condition (which not necessarily will be reflecting “perfect”)


mit freundlichen Gruessen/Best Regards


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