Thank you for this generous information regarding 13dB(A) nature
recording mics Klas! There are current discussions about
experimenting with the FET circuit for PrimoCorp and other capsules
on the Micbuilders list http://groups.yahoo.com/group/micbuilders/
in case you are interested in reading some. I'm sure your input
would be valuable. Rob D.
= = = =
At 7:04 PM +0200 9/21/05, Klas Strandberg wrote:
>The capacitance of EM23 differs between 65 and 80 pf. This is why the
>sensitivity differs between the samples.
>
>If you want to build your own preamp for it, you can use the FET 2SK170.
>Best case, you can get the noise down to 13 db(A).
>
>To connect the EM23 to the FET, - best is to use a gold-plated HQ device of
>some kind. You can solder directly on the gold plated outlet, but you have
>to be good at it. No beginners work. The plastic will melt. After
>soldering, seal possible air-intakes around the outlet with quick-glue.
>Do NOT!! take the capsule apart! You won't get the pieces back into
>position again.
>
>Klas.
>
>At 17:16 2005-09-21, you wrote:
>>I asked the questions because I am evaluating a new Ultra Sensitive
>>ECM. Its a electret capsule not yet avail in the US. Since the
>>naturerecordists group uses self-noise so often to compare mics I wanted
>>to know what the noise output of this new capsule might be. The mfr does
>>not include noise output in its spec. These are the guys that make the
>>EM23 cartridge.
>>
>>http://www.primocorp.co.jp/product/PDF/EM158.pdf
>>
>>The mfr characterized 5 samples for me and I'm currently trying to build a
>>mic around them. They may not be suitable for many DIYers because they are
>>very delicate physically. For instance the housing is much thinner than
>>paper and the characteristics can easily change with the introduction of
>>high heat from a soldering iron.
>>
>>The sensitivity of the 5 samples ranged from -28 to -31 dB
>>
>>Thanks guys for all the help. I'll study the rane.com references and
>>maybe someday I won't be such a newbie.
>>
>>The 1st one I assembled seemed to perform as good or better than my
>>183's. I have a pair of 183's I use as quasi-binural and another pair in
> >a parabolic. I use a NH900 and a RH10 for my recorders.
>>
>>I feel it may be appropriate to move any further discussion to the
>>micbuilders group.
>>
>>Thanks,
>>Gene
>>
>>
>>Rob Danielson <> wrote:
>>At 4:22 PM -0700 9/20/05, Dan Dugan wrote:
>> >Eugene E Dorcas wrote:
>> >
>> >>Can you calculate the output noise from other specs such as
>> >>signal-to-noise ration and sensitivity??
>> >>
>> >>For instance: If the sensitivity is -32dB and the SNR is 75 dB,
>> >>what would the output noise be??
>> >
>> >Mic signal-to-noise is measured from 1 Pascal, which is 94dB SPL.
>> >
>> >If the SNR is 75dB, you can calculate the self noise of the mic:
>> >94-75 = 19dB SPL (probably the SNR was spec'd in dBA, if so it would
>> >be 19 dBA).
>> >
>> >The sensitivity is more relevant to the question of whether that mic
>> >would get its own noise above a particular preamp's input noise
>> >level, called Equivalent Input Noise (EIN). If it does by more than a
>> >few dB, then you can get the best performance from the mic.
>> >
>> >http://www.rane.com/note145.html
>> >
>> >The noise output of a mic with 75dB S/N and -32dB sensitivity (very
>> >hot!) would be -(75+32) = -107dBV. dBV because the sensitivity is
>> >measured re 1 Volt (1Pa/1V).
>> >
>> >0dBu is 2.2dB below 1V (don't ask), so the noise output voltage of
>> >the mic in Haleakala crater would be -104.8dBu.
>>
>>Professor Dugan, I signed up for the course in Audio Measurement
>>Reference Levels, again. Charts 3 and 4 here
>>http://www.rane.com/note148.html show mic sensitivity as -dBu and as
>>mV/Pa. Seems not to be a simple arithmetic relation/conversion. What
>>is the "-32 dB" sensitivity measurement you are working with
>>referenced to or need it be? Rob D.
>>
>> >That would be way
>> >above the noise of even a commonplace preamp (like EIN = -125dBu). A
> > >mic with 10dB lower output than yours, like the Shure WL183, is still
>> >hot enough to make the noise of a cheap preamp irrelevant.
>> >
>> >Another confounding factor would be that preamp EINs used to be
>> >measured in dBm, and some still use that measure. Let's not go there,
>> >either. Any real audio engineers here, please check my figures.
>> >
>> >-Dan Dugan
>> >(I'm not an engineer, but I play one at work.)
>> >
>> >
>>
>>
>>
>>[Non-text portions of this message have been removed]
>>
>>
>>
>>
>>"Microphones are not ears,
>>Loudspeakers are not birds,
>>A listening room is not nature."
>>Klas Strandberg
>>Yahoo! Groups Links
>>
>>
>>
>>
>>
>>
>>
>>
>>[Non-text portions of this message have been removed]
>>
>>
>>
>>
>>"Microphones are not ears,
>>Loudspeakers are not birds,
>>A listening room is not nature."
>>Klas Strandberg
>>Yahoo! Groups Links
>>
>>
>>
>>
>
>Telinga Microphones, Botarbo,
>S-748 96 Tobo, Sweden.
>Phone & fax int + 295 310 01
>email:
>
>
>
>
>
>
>"Microphones are not ears,
>Loudspeakers are not birds,
>A listening room is not nature."
>Klas Strandberg
>Yahoo! Groups Links
>
>
>
>
--
Rob Danielson
Film Department
University of Wisconsin-Milwaukee
[Non-text portions of this message have been removed]
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