Hi Paul--
Such a chart would be an excellent shortcut for recordists if it
listed confirmed/tested recorder/pres for each mic. Some of the mics
and projected minimum EIN ratings for pre transparency are right on.
Others are off. Here are a few examples:
Rode NT-1A 25 5 -118.83 -128.8 dBu YES, A-weighted
Rode NT-2A 16 7 -120.70 -130.7 dBu?? Side by
side, the 2A is noisier than the 1A. In practice one could get by
with a slightly "noisier" pre, not a "quieter" one and one would not
need -130.7 dBu (A weighted).
MKH-40 25 12 -111.83 -121.8 ?? A few years back when we
were trying to get a input noise measurement for Hi-MD recorders, a
few folks independently noted that one could barely detect the input
noise of the pre at high gain using an MKH-40. Raimund (and others)
measured the Hi-MD recorders at -124dBu (A weighted). For pre
transparency with that mic, I'd go with a pre measure EIN of -125dBu
or higher, not -122dBu.
We live by the Raimund's measurements and there are discrepancies
between his and the manufacturers'. I'm sure its the same for the mic
specs. A chart in a similar spirit might have a list of mics and for
each mic, the noisiest EIN/recorder that has been tested as
transparent. That would give us comparable reliability.
A relation I can remember that makes things simpler for me is,
"..."pro-quality" low- noise, mic pre performance effectively starts
around -127 dBu (A weighted) because its input noise is quiet enough
to hide behind the quietest of mics. " http://tinyurl.com/yg2oopb
On the opposite end, if one is going to use mics with greater than
18dB(A) self-noise in high gain situations, there's not a lot of
quality to re-coop in pre choice. Rob D.
.
At 3:27 PM +1100 3/31/10, Paul Jacobson wrote:
>Hi All,
>
>The issue of mic output noise seems to come up fairly regularly in
>relation to recorder preamp noise levels, so rather than manually
>looking up the information of the Rane website every time I've
>created a spreadsheet to calculate the mic output noise from
>self-noise and sensitivity specs. The spreadsheet shows the
>calculated mic output noise figure and a suggested minimum preamp
>EIN based on Ranes 10dB "safety margin". I've currently got a
>limited selection of mics listed so if anyone has suggestions I'll
>add them to the spreadsheet.
>
><http://spreadsheets.google.com/pub?key=tzWtnN7a8lCBem84-DzS8vA&single=true&gid=0&output=html>http://spreadsheets.google.com/pub?key=tzWtnN7a8lCBem84-DzS8vA&single=true&gid=0&output=html
>
>or
>
><http://bit.ly/Mic_Output_noise_chart>http://bit.ly/Mic_Output_noise_chart
>
>The chart is probably most useful when used in conjunction with the
>Microphone Input Noise Comparison tests at
><http://www.avisoft.com/recordertests.htm>http://www.avisoft.com/recordertests.htm
>
>cheers
>Paul
--
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