At 9:31 PM +0200 7/28/05, Klas Strandberg wrote:
>At 20:47 2005-07-28, you wrote:
>>Let me try to re-state Klas' message:
>>
>>1. Each mic has a self-noise level, produced by the components in its
>>design.
>>
>>2. The recorder pre-amp cannot cancel or compensate for the mic
>>self-noise level. This mic noise level will always be part of the
>>recording.
>>
>>3. The recorder pre-amp has a self-noise level of its own. This noise
>>is also added to the recording.
>>
>>4. If the mic output signal is strong (i.e., has high mV/Pa), it can
>>over-ride the noise of the recorder pre-amp.
Yes! Excellent. A couple of nit pic "real circumstances" extensions,..
If the self noise of the mic is higher than the "effective self
noise" of the pre (and most of the time this is true with or good
pre like the 722 or, as we found, even the lowly HIMD if properly
out-fitted and no longer compromised), then, there is very little or
no noise from the pre to over-ride! That is-- the mic has already
buried it.
The test I posted seems to indicate the noise from the HiMD pre is
right around the self noise of the mic, "effectively ~6dBA*." Above
half of the noise I EQ'd out I could tell was from the mics because
it was different in each channel. I could also distinquish some very
narrow bands of noise that seemed to be a 722 contribution, not the
mics.
[* I say "effectively" because we're listening to/comparing the end
results and judging the difference not really measuring dBA's of self
noise in the pre]
> >
>>5. If you use a mic with low inherent self-noise and strong output,
>>you can achieve good quality recordings with a recorder that has a
> >noisy pre-amp.
And I hope people don't confuse price with "noisy" here. The lowly
HiMD tested is NOT an example of a noisy pre-- it has maybe 1-3dB
more noise but only at narrow selected bands? That's out of the
~133dB range.
Also note also that while preamp gain doesn't affect noise the way I
tested it, at max gain with all wrinkles showing, more gain in the
sound file under quiet conditions enables more bit saturation and
more ability to do effective filtering, volume boosting etc in post
etc. The HiMD has 5dB more gain than the 722 helping one get more
performance out of 16 bits rather than 24.
Klas, Oryoki, anyone,.. Clobber me if you think I'm wrong on any
point(s). This is important stuff to get straight. Rob D.
>Thanks, excellent summary!
>
>>In practice, this seems to be true. The Marantz PMD670 is a prime
>>example of a recorder with noisy preamps (Marantz claims s/n -65dBA),
>>but Martyn Stewart's recordings using Sennheiser MKE and Telinga mics
>>sound great.
>
>Also in theory. It is just logics.
>
>>I guess the place I'm having trouble is in the notion of "over-riding"
>>the recorder preamp. Klas, do you mean that when a mic has a high
>>mV/Pa, you don't have to turn up the volume of the recorder pre as much?
>
>Yes. Exactly. If enough gain is produced by the "optimized" pre in the mic
>(minimum self-noise!!) - you don't need so much gain in the recorder pream=
p.
>
>Klas.
>
>
>>--oryoki
>>
>>
>>
>>
>>"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
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