[Elecraft] bias for Yamaha CM-500

[Don Wilhelm]

David,

It is not critical.  Look at the reflector post by Jim Brown in the last 
couple days - I received it 01/15/2010 at 12:06 Eastern time.  Jim is 
quite familiar with the microphone and explains it much better than I can.

73,
Don W3FPR

David Christ wrote:
> I'm trying to understand the bias requirements for the CM-500 
> specifically and electret/condenser (which is it) mikes in general.
>
> Yamaha's adaptor uses 3V  (2 AAA batteries) in series with a 2.2K 
> resistor and a 1 microfarad DC blocking capacitor.   I would rather 
> not depend on batteries.  My reading of the KSB2 manual says to use 
> 10K fed from 5V while I have heard that it should be 10K for this 
> unit. I am not sure what my K3 is supplies.  I would also like to use 
> the mike with a Kenwood TS-940.  That rig has 8V available at the 
> mike connector.  So if I build an adaptor to use with that rig what 
> is the proper value resistor to use?  Or should I build a quickie 3V 
> regulator fed from the 8V and then use a 2.2K resistor?  I presume I 
> would need some value of DC blocking capacitor for the Kenwood.
>
> How does one determine the proper voltages and resistance values?  Is 
> it to get a specific voltage, current or what?  How close do you have 
> to be or is it non-critical?  What difference does it make?  Where 
> can one find information?
>
> Thanks all from an old timer who is still trying to get up to date 
> from the dynamic and crystal mikes of the 60s and 70s.
>
> David K0LUM
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