Testing Neumann without capsule

[mitsos]

Need to test some old KM's.. Neumann's old lit shows an MA adapter which fits in place of the capsule, which imitates the capsules capacitance, and allows you to inject a signal without the capsule. Since I don't have one of these adapters, can someone help me make a rig to do what they do?  Is it a matter of removing the capsule and strapping a capacitor in it's place?
tia!

 

[MagnetoSound]

Is it a matter of removing the capsule and strapping a capacitor in it's place?

Yes it is. You also need to think about shielding the end of the mic (where the capsule isn't) from hum.

 

[mitsos]

Thanks for the confirmation.  So the capacitor connects to where the capsule normally goes and signal is injected post cap?  I think neumann has published capacitance specs, so use that value as a base? 

 

[MagnetoSound]

Yes, you should approximate the capsule value as closely as you can.

Which KM series is it? The KM5x (and KM25x) have a calibration input already provided.

 

[mitsos]

KM86i. Beautiful mic, wish it were mine!

 

[soapfoot]

try 30-40 pF

 

[bockaudio]

you could also build a box w/shielded connectors, put the mic (with it's body removed & dummy capsule in place) in the box and feed the test signal in. Then the box acts as the hum shield and you have room to play.
I built one years ago and it is indispensable.
40pF for small D, 80pF for large. use polystyrene or mica.

 

[mitsos]

thanks guys.  david, that's a great idea!  A good shielding solution is the hardest part.
cheers!

 

[pucho812]

mitsos your PM box is full. Did you get the schematics?