Do old electret capsules go bad with time? ( GenRad 1560 mics )

zebra50

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Jun 4, 2004
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York, UK
Hi there,

I have a couple of 1960's GenRad measurement 1560-p42  mics on the bench, which are beautifully engineered, but seem to be pretty noisy.  The noise is wind/woosh/hiss, like a dirty capsule.

I don't have a lot of experience with old electrets. Does anyone know what happens as they age? I seem to recall reading that the polarisation fades with time.

I'll post up some photos later as they are really quite wonderful to look at.

Anyway, thanks for any thoughts or comments.

Stewart
 

mad.ax

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Jul 22, 2007
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france
Hello Stewart,

I guess you are familiar with this page?
http://www.soundfirst.com/GenRad.html

The general consensus seems to be that electrets do not age well, with the notable exceptions of B&K (who put their electret capsules through a 'pre-aging' process, whatever that means) and Sennheiser.

Perhaps you should try the mic with a new cheapo electret and see if the noise disappear?

Axel
 

Gus

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Jun 3, 2004
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http://www.soundfirst.net/images/GR/1560-P40(12).jpg

interesting preamp

Can you sub in a cap for the capsule maybe 35pf (a guess) and test if it is the capsule and/or amp causing the noise
 

zebra50

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Jun 4, 2004
Messages
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York, UK
Thanks for the comments,

I have two capsules and two amplifiers. One capsule seems more noisy than the other.

>Can you sub in a cap for the capsule

That is a good idea, but I don't want to solder onto the nice gold plated  screw thread. I'll see if I can just clip one in place. It is pretty much impossible to get inside the preamps.

Stewart
 
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