Raimund,
To be fair, those could be the correct numbers if the overall gain is very
low (for example, if the noise figure was calculated at 13 dB gain rather
than 53 dB gain) and the 0 dBFS level is very high (like 1000 v or somethin=
g
absurdly high). Since the unit is primarily intended for concert recording
it might likely be used at low-gain settings, though it is still very
unlikely anyone will get 1000+ volts out of any known mike, even at an AC/D=
C
concert.
But to be even more fair, a recorder with 40 dB dynamic range will record a
concert just fine provided the preamp & A/D don't clip.
Bruce Wilson
http://science.uvsc.edu/wilson
-----Original Message-----
From:
On Behalf Of Raimund Specht
Sent: Thursday, December 14, 2006 8:35 AM
To:
Subject: [Nature Recordists] Re: A good solution?
sveinung_nygaard wrote:
> > The noisefloor on the preamp from Core Sound...
> > maybe too good to be true?
oryoki wrote:
> The $500 Core Sound states that the self-noise of its Mic2496
> portable preamp is -135dBFS. The excellent portable preamps
> from builders like Sound Devices, Sonosax, and Aerco claim
> self-noise figures around 125 dBu. If I remember correctly,
> the dBFS scale is about 20dB different than the dBu. So converted
> to dBu, the Core Sound device's self noise would be rated
> around 115 dBu.
The impressive noise figure of -140 dBFS at
http://www.core-sound.com/Mic2496/2.php is obviously the FFT magnitude
level and not the common broad-band (rms) noise level. The FFT
magnitude noise level will depend on the frequency bin width
(determined by the FFT size and sample rate). Unfortunately, they do
not specify that.
To my knowledge, the best A/D converters chips that are currently
available provide a dynamic range of up to about 123 dB (broad-band rms):
http://www.asahi-kasei.co.jp/akm/en/product/ak5394a/ak5394a.html
So, the 140 dB figure just seems to be a marketing gag to impress
customers.
Best regards,
Raimund
"Microphones are not ears,
Loudspeakers are not birds,
A listening room is not nature."
Klas Strandberg
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