'Conducting' M7 capsule mount?

[RuudNL]

I am having problems with a mount for a M7 microphone capsule.
I measure a resistance of 200-300 M.ohm.
The base is a 'rubber like' material, but it causes a leak current in the microphone circuit.
(The voltage on the backplate gets reduced because of this leak current.)
Is this a known problem, or am I the first one with this situation?

 

[Drosselmeier]

original capsule?

 

[Moby]

I am having problems with a mount for a M7 microphone capsule.
I measure a resistance of 200-300 M.ohm.
The base is a 'rubber like' material, but it causes a leak current in the microphone circuit.
(The voltage on the backplate gets reduced because of this leak current.)
Is this a known problem, or am I the first one with this situation?

I never measured it but I trashed few of them because it looked suspicious. Especially the material used for the "shock insulation". Resonance frequency of the material was too high. But now when I double think maybe the electrical insulation was the weak point too. Can you post the photo of your "bad mount"?
BTW, did you try to demoisturise it and measure again?

 

[pH]

This happened to me while building the MK7 into a Thomann donor microphone, rumbling noise was driving me crazy and it wasn't until I isolated the mount with mica wafers and screw insulators that the noise went away.
Later when I replaced it with a better quality mount the extra insulation wasn't needed.

 

[mad.ax]

Is this a new rubber mount? Or an old one?

Rubber doesn't age nicely. It develops a lot of micro cracks, and those cracks make very comfy places for the moisture to spend the winter in...

I suspect this problem to be quite common despite remaining 'unknown' because most people don't have the tools to measure such high Z.

Axel

 

[RuudNL]

Is this a new rubber mount?

It is a brandnew one!

 

[kingkorg]

I am having problems with a mount for a M7 microphone capsule.
I measure a resistance of 200-300 M.ohm.
The base is a 'rubber like' material, but it causes a leak current in the microphone circuit.
(The voltage on the backplate gets reduced because of this leak current.)
Is this a known problem, or am I the first one with this situation?

Tja, who cares. Just use the resistance to bias the grid, pattent it, come up with a story, become rich
Humor aside now i have to check mine.

 

[mad.ax]

Brand new and only 200 to 300 MΩ ! Something is wrong here.
Please tell us who the supplier is so we could cross it off our list...

Axel

 

[RuudNL]

Tja, who cares. Just use the resistance to bias the grid, pattent it, come up with a story, become rich

Unfortunately it seems it is a pretty noisy resistor!

 

[Moby]

It is a brandnew one!

That's the one. I can't be 100% sure but I think that Chineese company who produce it use some recycled polymer what contains the metal practicles (dust). Typical for most of the products nowdays. They can't save on labour anymore so it comes to the material savings.

 

[Moby]

I found a local vulcanising shop who made me the custom vulcanised insulators.

 

[nielsk]

I had this problem before with a new mount for the "Dale" M7 capsules that was made available on the forum. It seems they used a rubber compound with carbon in it! (pretty standard to use carbon to make rubber black, actually)
Took me some time to figure it out! I got a different mount and all problems were gone...

 

[TLRT]

Yes I had the same problem some years ago.