[TenTec] Electret Mic voltage vs. Dynamic Mic

[Stuart Rohre]

Rod,
Since a dynamic mike is an electromagnet element, you MUST NOT allow DC to get
to it.  At worst you will burn out the winding.  ADD a blocking capacitor, or
two back to back electrolytics, for a non polar low frequency pass cap.  Or by
the non polar electrolytics.  Check the schematic for what the bypass
electrolytics, or coupling electrolytics are in the mike circuit and use at
least that value.  I imagine anything around 50 MF will work, and the voltage
to be at least twice the DC on the connector.  Place this in series with the
hot lead of the mike element.  Now the value I am suggesting may be large, but
is predicted for a 500 ohm impedance dynamic element typical of modern
elements.  Older dynamic mikes had higher impedances on the line, and could
use as small as a 1 MF cap.  You can tailor your response to be less bassy by
using a smaller value cap, (less MF).  Try what you have in the junk box, and
see how you sound.

GL and 73,
Stuart K5KVH

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