Hi Henry:
My rules of thumb when transferring from analog sources:
1. don't overdo levels at any stage of the analog chain. Know your gain stages, know your headroom
on all pieces of equipment, work accordingly.
2. always transfer at high resolution, 96/24 seems to be the resolution specified in most
grant-funded projects on which I've worked. I believe it is the standard specified by NARAS. Working
at 24-bit allows you to be conservative with ingestion levels.
3. since almost all DSP effects ultimate digital levels, you want to leave plenty of headroom in
your raw ingestion file. I never go above -6dBfs peak level, and usually stick well below that. I am
conservative with DSP, so I've never had a problem where something like NR, EQ or tick and pop
removal brings the peak level anywhere near digital zero. If you're more heavy-handed, give yourself
more headroom to be safe.
4. final "master" product should be peak-normalized. There has been some controversy about this over
the years, mainly because cheaper-design CD players' post-DAC analog stages have no headroom and
thus audibly distort before digital zero, plus there are problems with "rips" to MP3 and other lossy
formats. Being conservative, I normalize peak levels to -1dBfs for non-dynamic content (ie rock
music) and -0.5dBfs for very dynamic content (ie well-recorded classical music). There were some
"toothpaste-compressed" analog products back in the day, especially rock albums late in the LP era.
Those sources are best normalized to a peak level of -2dBfs so they seem a little bit less
"super-loud" when played back with other material or combined into iPod playlists. They'll still
seem "too loud" compared to well-produced audio.
So one question that comes up in all of this is "what is 0VU on my console as far as dBfs in my
DAW"? Assuming 0VU = +4dBm, and you have your mixing console set accordingly, I think you're safe
with 0 = -12dBfs, but I think one more conservative standard out there calls for 0 = -14dBfs. I
can't see how that hurts in a high-resolution digital environment, so nowadays I'd advise go for the
more conservative standard. In reality, there is NO content that's really "90dB" unless it's made in
an anacholic chamber, and no one would want to listen to it. The best classical music has about a
30-40dB dynamic range as far as audible ppp to audible fff (yes, it's possible to get 60dB in a good
quiet venue using digital recording, but very few listeners will be able to hear that without riding
the volume control). Well-recorded jazz can be in the 12-15dB dynamic range, sometimes a bit more.
Rock music rarely has dynamic range of more than 6dB ("half as loud to twice as loud").
Toothpaste-mastered stuff literally has less than 1dB dynamic range, it's just an annoying onslaught
of sound.
I'm interested in other comments. Are others operating under very different rules of thumb?
-- Tom Fine
----- Original Message -----
From: "Henry Borchers" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Friday, October 19, 2012 9:51 AM
Subject: [ARSCLIST] Analog to digital dBFS standards
Hello all,
I've been hitting a brick wall with my research and I was hoping that with all the experts here,
someone could point me in the right direction. I’m currently looking for research done on digital
reference levels. I am particularly interested in looking for references related to the amount of
headroom standards digital audio archivists and audio digitization technicians use in their digital
masters and the digital level dBFS that analog equipment have been calibrated to. I’ve been able to
find a lot of references about dBFS standards when it comes to audio for DVD, TV, and cinema (such
as SMPTE standards) but not much for the digitization of audio only content. I have been having
trouble locating good research regarding this area and I was hoping someone here could point me in
the right direction..
Thanks,
Henry
--
Henry Borchers
Broadcast Media Digitization Librarian
University of Maryland
B0221D McKeldin Library
College Park, MD 20742
(301) 405-0725
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