Sennheiser MKE44-P EMI/RFI help

Hey folks,

I have a Sennheiser MKE44-P, stereo mic, that is quite sensitive to smart phone data signals.  The old "blip blip berzzzz blip blip".  I snipped the long, un-shielded leads from the capsule to the preamp input and soldered in some ferrite beads that I pulled off an old PCB that I had lying around for spare parts.  I don't know the beads' value.  It did help significantly, but there is still a little fizzle making it through.  I'm thinking of trying some capacitors either 220pF or 1000pF to see if that will shunt the remaining fizz.  Any thoughts?  I talked to a tech at Sennheiser.  They were very helpful.

Thanks,
Danny

Nanitlig said:

Any thoughts? 

Click to expand...

Yeah.

A sign in the studio that says "All cellphones will remain OFF during recording".

While catching a nap in the sleeper at a live show, my phone rings, it is FOH, "Your PA is making a weird noise".  So I wipe the sleep from my eyes, haul ass inside and make my way to FOH, to find the cellphone of a very experienced engineer who should have known better, leaning on the meter bridge propped up by a couple of input attn knobs. I snatch it off the board and hand it to him. You could see the light bulb illuminate above his head. "Phones do that?" I simply gave him a "you idiot" look, and went back to sleep.

Gene

I think I figured out the issue.  A roughly one inch section of the microphone body, between the capsule assembly and the handle, is made of plastic.  The leads, from the capsule pin/socket connection to the preamp, in the handle, are long, flat wires that pass through this section of the mic without any shielding.  Poor design.  Of course, 25+ years ago it wasn't as big of an issue.  My next attempt will be a solid coating of conductive paint and making sure it is grounded.  Wrapping the mic with shielding foil and grounding that does a good job, but doesn't look very nice.  Short of building a Faraday blimp to put the mic inside or paying someone to machine a new handle/housing for the mic and electronics, the paint seems like the next best thing to try.

..or the amplifier part developed a slight nonlinearity (e.g. worn capacitors?) over the last 25years, that influences hf-noise rejection?

Sennheiser are not known to take interference issues lightly..

Jakob E.