I see. Interesting. I probably shouldn't worry about this, but I can't help
myself! If the input and output impedances are nearly equal, the input voltage
is being cut in half, correct? And that would mean that the output noise is
getting very close to the LS-11 EIN limit.
Is it difficult to modify the battery box circuit for the mic capsules to lower
the output impedance? I am using 6.8k resistors with a 9v battery to power two
EM172 capsules.
circuit diagram:
http://www.megalithia.com/elect/BATTBOX.pdf
many thanks,
John
John Crockett
Westminster, Vermont
--- In "Raimund" <> wrote:
>
> > I had not realized that the EM172 capsules have such a high impedance
> > (2.4k ohms), higher than the mic input on the LS-11.
> >
> > I did a quick experiment running the EM172s through my ART preamp,
> > which has an input impedance rating of 300k ohms, and I do not hear
> > any difference compared to the LS-11 which is rated at 2k ohms.
>
> Hi Jon,
>
> If you don't hear a difference between the two setups, then the EIN of the
> LS-11 is obviously still low enough for properly processing the reduced
> output signal level of the microphone.
>
> The drop of the output signal voltage is however a matter of fact that can be
> easily derived from ohms law. Further details on this issue can also be found
> for instance at rane.com:
> http://www.rane.com/note124.html
>
> > Is there an ideal amount by which the microphone output impedance
> > should be lowered compared to the preamp input, and is there a
> > standard method for doing this?
>
> I agree whith Dan that a factor of at least 10 would be ideal.
>
> Regards,
> Raimund
>
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