DAT-heads Digest #397

Contents:
  Re: emphasis (Bob Ramstad)


From: Bob Ramstad <rramstad@gmail.com>
Subject: Re: emphasis
Reply-To: rramstad@alum.mit.edu
Date: Sat, 19 Feb 2005 12:54:05 -0800

Bill Shaw <Bill.Shaw@hds.com> wrote:

> Subject: Re: emphasis
> Date: Fri, 18 Feb 2005 10:27:24 -0800
> 
> Another option, I believe the simplest, would be to play the tape back on a
> deck that supports emphasis. (Teac DAP20 for instance and some JVC home
> decks).

I'm baffled.  Maybe I'm confused, but I believe the original poster
was talking about transferring DAT to CD.

If you playback on a DAT deck that supports emphasis (I believe all of
them do, by the way) the digital output will have valid digital audio
data, and that digital data will have the preemphasis flag set.

When you route this into a computer, via whatever means, the resulting
WAV files which are created cannot store the fact that the data needs
preemphasis.  There is no preemphasis flag in the WAV format.  I am
not aware of any common digital audio format for computers which has
the ability to store the preemphasis flag.

Now, if you are suggesting that someone could use the *analog* outputs
from a DAT deck that supports preemphasis, yes, this would work, but
you are introducing a whole bunch of extra noise and hassle in the
process going from digital > analog > digital just to remove the
preemphasis.  It is especially problematic to get the analog input
into a computer without introducing all sorts of RF noise.

I stand by my earlier comments, included below.  If you are mastering
CDs from DATs that have preemphasis, it is a good idea to deemphasize
in the digital domain so you end up with garden variety WAV files that
no longer require special handling.

I hope this helps, and if I've totally missed the point, my apologies.

-- Bob

> > -----Original Message-----
> >
> > From: Bob Ramstad <rramstad@gmail.com>
> > Subject: Re: emphasis
> > Reply-To: rramstad@alum.mit.edu
> > Date: Thu, 17 Feb 2005 10:42:46 -0800
> >
> > It is absolutely critical when transferring from DAT to WAV or similar
> > to account for preemphasis.
> >
> > That said, there are many ways to skin the proverbial cat if you are
> > doing a digital transfer.
> >
> > 1) (Recommended earlier by another poster)
> >
> > Use a CD burning program that supports setting the preemphasis flag,
> > and if you keep the WAV files around as data, make sure you keep notes
> > that they require preemphasis.
> >
> > Pros: least manipulation of the data so the result is essentially
> > identical to the source DAT
> >
> > Cons: some idiots will inevitably do a DAE on the audio CD and then
> > wonder why the result sounds like crap, or burn the WAV to audio CD
> > without setting the preemphasis flag and wonder why the result sounds
> > like crap, or will listen to the WAV file through WinAmp or similar on
> > a computer and wonder why it sounds like crap
> >
> > WAV files do NOT have a space in them for noting if the preemphasis
> > flag is set or not, and as a result, it's super easy for this
> > information to be lost.
> >
> > 2) (New suggestion)
> >
> > If you have an appropriate sound editing program and are doing other
> > extensive work on the recording -- resampling, normalizing because
> > levels are really low, and so on -- most editors have the ability to
> > apply preemphasis which will result in corrected WAV files.
> >
> > Pros: possible for people to listen to the WAV directly and have it
> > sound good, impossible for people to screw up later
> >
> > Cons: if it isn't done properly, the correction of preemphasis can
> > introduce audible artifacts... modern software shouldn't have this
> > problem.  That said, there is a slight digital generational loss by
> > doing this process, much like resampling.
> >
> > Long story short, if you are going to be doing any extensive work on
> > the audio, especially resampling, it would be an excellent idea to
> > also deemphasize in the digital domain.
> >
> > One program I know of that does the deemphasis is sox, which is kind
> > of a swiss army knife type tool that runs on Linux.  I think any of
> > the standard DAW type programs (Sound Forge et al) should have
> > deemphasis functions, though.
> >
> > I've only dealt with one recording with preemphasis, and the results
> > turned out pretty good, I tried both methods and ultimately decided
> > the corrected version was easier in the long run.  I imported the 44.1
> > kHz DAT at 24 bits, deemphasized, then did a bunch of other work
> > including normalization and some fades and correction of levels in
> > various places, then went to 16 bits for CD audio.  If I was doing it
> > again today, I'd probably do the same thing except import at 32 bits.
> > It was a long time ago but I think I used Sound Forge for everything.
> >
> > Hope this information helps!
> >
> > -- Bob
> >


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