about the md 21. it is a dynamic microphone. many dynamic microphones are i=
ntrinsically lower noise than condensors, but they have also low output. mo=
st of the mic preamplifiers I see these days (the exception is the 722) do =
not amplify these low output microphones well. In the ancient days, Nagra m=
ic amps produced exceptionally low noise using germanium transistors and a =
largish transformers. the transformer is the key. it can provide upto 20 db=
=A0 of noise free gain.
=A0
umashankar
>________________________________
> From: Avocet <>
>To:
>Sent: Sunday, December 16, 2012 6:34 AM
>Subject: Re: Summary: [Nature Recordists] Re: EIN values and bits and pea=
ks
>
>> I have a long list of such "mysteries" that I would very much like
>> to
>> have explained, at least on a basic level.
>
>Klas,
>
>Here's one possibility. Many mics have low impedance outputs and are
>quoted for running into a higher impedance than the rated 150 or
>200ohms. There is a mysterious parameter called "noise impedance"
>which is often different from the mic output impedance or the
>mixer/recorder input impedance. The noise impedance is the optimum
>impedance for minimum noise.
>
>Some mics quote a minimum input stage impedance of 2000 ohms or
>higher. If a recorder input is lower, say 200ohms, it will match the
>mic output impedance for a good frequency reponse but may not be
>optimal for the noise impedance.
>
>Another possibility is noise from a phantom powering circuit which
>should balance out. If the mic or the input amp is not fully balanced,
>this is a route for different noise levels from those quoted.
>Transformer inputs balance the input and feed this into an unbalanced
>front stage. Direct transistor balanced inputs use positive and
>negative input stages and add these to balance the audio, but not
>necessarily the noise.
>
>David
>
>David Brinicombe
>North Devon, UK
>Cogito cogito ergo cogito sum - Ambrose Bierce
>
>
>
>------------------------------------
>
>"While a picture is worth a thousand words, a
>sound is worth a thousand pictures." R. Murray Schafer via Bernie Krause.
>
>Yahoo! Groups Links
>
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