Tube condenser mics crapping out

[Radardoug]

You require a huge SPL to make a condenser mike bottom out. Or are you putting it in a kick drum? What is your high SPL source?

[jackinthebox]

A particularly loud drummer as a mono overhead and very loud brass apparently pushed it over the edge. I am surprised at mic bottoming out at sheer SPL which made me think wind blast might be the issue, but above a drum wouldn't be a very windy spot.
Could very low frequencys overload the amp to point of cutting out?

[Tim Campbell]

Dear Jack,
Old style (brass) Ck12 type capsules cannot handle SPL levels like center terminated ones. If you're collapsing a K7 (M7 type center terminated) then the SPL's must be pretty high.
You could move it farther away or use a pop filter in front of it. Any capsule that bottoms out repeatedly is going to have a much shorter working life than one that was handled with more care. I've seen CK12 capsules that were used to mic guitar cabs who's membranes resembled the surface of the moon from slamming into the backplate not to mention what it does to membrane tensioning.

Both these capsules are great at capturing detail, others are perhaps better at handling SPL's.

[jackinthebox]

Thanks for the reply Tim!
I think you are probably more qualified than anyone on the planet at the moment to comment on edge terminated capsules. I have not experienced the bottoming out myself and I haven't been able to test the mic properly to find out what the cause of the problem might be. I did suggest using a pop filter to see if that would remedy the problem so hopefully that will solve it. I am assuming it is the capsule as I can't imagine what other component would cut out under extreme conditions, but there may be some other cause that I am not yet aware of. The mics sound really wonderful but the only complaint has been the SPL issue. Apparently an original 47 was used instead which didn't exhibit the same problem. I guess an old M7 has a much thicker diaphragm which make it less susceptible to wind or excess pressure perhaps?
I will definitely be ordering several more of your capsules in the near future though. They sound incredible!
Thanks again for your reply.
Jack

[gyraf]

What preamplifier are you using?

Many tube mics has very high output levels, and can possibly overload the input stage of simple micpres, i.e. circuits that does not have input attenuation at low gains...

As a check, you could take the mic in through a line input to exclude this as the problem's source...

Jakob E.

[jackinthebox]

On another forum it has been suggested that it may be the power supply running out of current when presented with a large transient peak. Any thoughts on whether this is possible? I will try putting beefier caps in the PSU and see if this makes a difference.

[jackinthebox]

API generally but we've used neves, early bird and various others. I built the mics for a client of mine so to be honest I haven't had first hand experience of the problem myself.