At 4:47 PM +1100 4/1/10, Paul Jacobson wrote:
>
>On 01/04/2010, at 8:38 AM, Rob Danielson
><<type%40uwm.edu>> wrote:
>
>> Its on the test "to-do" list. I'm not following how rec gain makes a
>> difference in mic self-noise performance and the resulting recording
>> if a sufficiently quiet pre is used. Such a pre would be necessary to
>> compare the self-noise performance of the two mics.
>
>Hi Rob,
>
>I'd like to to compare noise output rather than self-noise as you
>have said that the calculated figures for the NT-2A are incorrect.
>The only way to determine if this is so is to record the two mics at
>the same gain level. :)
Hi Paul--
I would use similar gain like that I'd use in the field for demanding
conditions. I think the concept of "noise output" might be most
relevant for pairing pres and mics when the pres are not sufficiently
quiet. If the mic/pre combination is "right," a mic with
significantly greater sensitivity and 2 dB(A) more self-noise could
create a signal with peaks that have more separation from the noise
bed if the gear combination is right. For example, not too long ago,
Raimund suggested using of a more sensitive mic like an ME-66 in
order to get more separation from the LS-10's input noise.
I agree with Raimund about careful coloration specs being the missing
ingredient. I would propose that in these match-ups between recorders
with -124 dBU (A weighted) of input noise and noisier and mics with
more that 12dB(A) self-noise, the coloration(s) of the recorder's
input noise and mic self-noise can easily play a larger role than the
absolute noise values which the Rane Table encourages us to rely on.
>In theory the NT-2A should be more revealing of preamp noise than
>the NT-1A due to it's lower level of noise output. I'm using lower
>in the sense that a noise level of -128dBu is lower than a noise
>level of -127dBu.
>
>> routinely used "28" for recording with Hi-MD in the field and most
>> of the tests I did were at "28." I'm not aware of anyone doing a test
>> showing Hi-MD input noise increases with gain (that its not
>> proportional). I'm open to the possibility.
>
>Preamp noise levels and distortion typically increase as you reduce
>the amount of gain.
In terms of analog electronics principles, I'm not qualified to say.
I try to restrict my conclusions to comparisons between specific gear
combinations and I only feel comfortable with opinions when these
generate considerable agreement.
When it was a hotter topic, I compared the pre performance of Hi-MD
at different gains and I couldn't detect a significant difference
between "20," "24" and "28". I believe that all of Raimunds' input
noise tests use max or near max gain to accommodate demanding goals
like recording ambience in quiet locations.
You are very correct that noise performance can vary with gain and
the difference can become significant. If one is using low noise
mics, testing this variable in an old or new recorder should be done.
Rob D.
=3D =3D =3D
>cheers
>Paul
>
--
"While a picture is worth a thousand words, a
sound is worth a thousand pictures." R. Murray Schafer via Bernie Krause
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