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Grex Hardware Item 147: Condenser Mic interface?
Entered by rtgreen on Sun Mar 1 22:05:13 UTC 1998:

I have a Realistic 33-1090b condenser microphone, in a PZM style pickup.
The microphone came with a small battery power supply / pre-amp and an
unbalanced output connector.  I have an application where it must feed
the recorder through a 50foot cable.  Needless to say, hum is a frequent
problem.

  The mixer has available some balanced inputs with phantom power.  Can
anyone suggest a source for a circuit which will use the phantom power
to bias the condenser mic element, and possibly pre-amp the signal, as
well as matching it to the balanced line?  Do I get lucky and find a
specialized integrated circuit that fits the bill exactly?

3 responses total.

#1 of 3 by scott on Sun Mar 1 23:13:36 1998:

Well, the Radio Shack PZMs I remember from a few years back are already low
impedance balanced, such that you could just cut off the molded 1/4" plug and
solder on an XLR.  I never did try to run one phantom power, but you could
run the little in-line preamp up to 12 volts, so soldering a 9v battery clip
on helps the dynamic range a bit.

(<sigh> they don't sell those little gems anymore... :(  )

#2 of 3 by n8nxf on Mon Mar 2 12:13:27 1998:

Sounds like an electrit mic to me.  Condenser mic and FET amp all in one
tiny package.  Very common, very cheap, decent audio response.  It,
however, requires a battery to power it.  It has a pretty low Z output
so should not be quite as sensitive to picking up AC hum.  Are you using
decent shielded cable to carry the audio signal?

#3 of 3 by rtgreen on Tue Mar 3 10:08:41 1998:

Thanks for the suggestions.

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