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16 bit vs 24 bit, 44.1khz vs 48 khz <-- please explain
In article writes:
My first
generation AD122 had 122dB (20 bits) and I called it a 20 bit
converter. Than all those 100-110dB devices apeared on the market with
"24 bits" on the panel and the sales guys insisted that I call mine a
24 bits. The bits are there, but the last few just bounce around
mindlesly - no realtion to the audio.
You're doing better than most, if not all. However, the term that we
throw around with reckless abandon is "24-bit" and not "24 bits of
resolution." Nobody said that those lowest order bits had to actually
carry information, they just have to be there so that a 24-bit
receiver will recognize the format.
I suspect that this may have been started by the A/D converter chip
manufacturers who wanted to produce chips with a 24-bit data word.
What goes in isn't their problem, it's the problem of the person
designing the application around the chip.
Do you need 24 bits AD? Probably not, short of some of the headroom
comments. What is the best Mic preamp out there? Say -130dBu? How much
gain is it set for? Say I use 30dB gain, than the noise floor is at
-100dBu and a peak to peak siganl out of the preampp is 24Bu driving
an AD. So we have 100+24=124dB
dynamic range. My AD122 MKII gives you 3dB margin. But say you need
40dB mic pre gain. Now you can use the 114dB dynamic range device...
I've just stirred up a discussion over on the Pro-Audio mailing list
about a related subject. How does someone who thinks that the
difference between a line level and mic level input is the kind of
connector used compare a the gain and noise performance of a preamp
which has only a digital output (integrated A/D converter with no
user-adjustable calibration) with a straight analog preamp and an A/D
converter of unknown input sensitivity for full scale (needless to say
and also unknown noise performance)? You can compare volts out to
volts in and get gain, or volts out for no volts in and get dB of
quiescent noise. But how do you relate volts in to dBFS on your DAW's
meter or headroom indicator? It's a different ball game, but trying ot
explain that you have to think differently about these things requires
more learning than some people (who buy by looking at spec sheets)
want to bother with.
--
I'm really Mike Rivers - )
However, until the spam goes away or Hell freezes over,
lots of IP addresses are blocked from this system. If
you e-mail me and it bounces, use your secret decoder ring
and reach me he double-m-eleven-double-zero at yahoo
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