-=> Quoting Herry Budiutama to Cameron Hall <=-
 HB> "Levels" as in recording levels?   What is the proper recording level
 HB> for Dolby B/C ?
The "levels" I was referring to had to do with the internal calibration
of the deck to the tape.  In theory, a recording should come off the
tape at the same recorded level it went on at.  However, each brand, and
each batch manufactured is slightly different magnetically.  Most of
these differences are small enough to be insignificant.  Thus, the
purist will buy a HUGE batch of tape, hopefully from the same production
run and take his/her machine to a reputable shop and have it optimised
for that brand and tape type.  Tape decks with front panel calibration
controls, or have built in automatic calibration don't require this if
it initially is set up correctly at the factory.
As to what the USER sets as an optimal recording level, is dependant on
the quality of the deck electronics, recording head, and tape quality
used.  The degree of distortion that the user accepts also depicts the
final record level.  And some manuafactures set the metering differently
from one another, not to mention meter reaction time to the source being
recorded.  The best way is to record the best sounding source you can
find, and start at the meters peaking at the decks "0" point.  Listen to
the recording.  If it's clean, re-record at "+2"  At some point, the
sound will become un-acceptable.  You then must record below that point
to ensure what you percieve as an acceptable recording.
 HB> My tape deck has an auto tape selector.  I suppose it changes
 HB> automatically to the correct EQ when I insert a metal or chrome tape.  
It does more than that.  It changes record bias, record EQ and playback
EQ.
 HB> But now I'm not sure whether or not its working because turning on
 HB> Dolby B on a metal tape causes the sound to be flatter than normal.  
 HB> (this doesn't occur to such extreme on a Normal Bias tape).
What do you mean by "flatter"?  In a perfect cassette deck (which
doesn't exist ) the tape would sound EXACTLY like the source.  Thus,
the comparrison between source and tape is the crucial factor.  With
Dolby on, whichever produces the closest match between tape and source,
is the closest match you'll get using a particular brand of tape with
that machine.
 HB> So, say that the EQ level is that of a normal bias tape when I made
 HB> the NR recording.  Will the playback sound flatter?  Or are metal
 HB> tapes not designed for NR recording since from your explanation, metal
 HB> tapes seem to do the same thing.   How do I test the tape deck whether
 HB> or not it has a broken tape selector?  (I was fine with a tape selector
 HB> switch, but nooo, they got to make it AUTO with no lights).
That's too bad about no indicators showing the tape selected.  Some
cheap tapes have been known to not have the correct holes at the rear of
the cassette shell, but that should have largely be gone now.  Metal
tape should allow a high record level without distortion.  If you can
acheieve similer results with type II (chrome), then there's a better
choice as it's more cost effective.  You'll have to decide that.
 HB> Now what is "Bias" anyway? :)
 
Bias is a high frequency (beyond the range of hearing) "tone" that is
applied along with the music to the record head.  Magnetic tape doesn't
record well without it. :-)  It would sound terrible. 
 HB> So basically, a tape recorded with Dolby NR must be played back with
 HB> NR ON, otherwise the sound will not be the same since Dolby alters it
 HB> during the recording process.
Exactly.  However, Dolby B processing is often played back in portables
and car units where the fidelity of the high's is muted, and the treble
"lift" given by Dolby B compansates for that a bit.
 HB> What if a tape is recorded with Dolby C or HX PRO but the playback is
 HB> on a machine that doesn't support C/HX.  Will the sound be compromised
 HB> if a C/HX recording is played back on type B machine?
 
Playing a Dolby C tape on a B type machine can be done, but odd things
happen to both the soft sounds and the loudest sounds.  No "damage" is
done, but it sounds odd.  You'll loose some of the highs and other odd
things happen.  Dolby HX (Headroom eXtention) is used JUST for recording
only, and what machine is used for playback doesn't matter.
 HB> But since the sound on the CD is digital, rotational accuracy will not
 HB> alter the sound, correct?   If the rotational problem is not minor,
 HB> then I presume the music will just skip, rather than degrade.
 
Minor rotation problems are dealt with by the error detection of the CD
format, and the speed adjusted accordingly.
 HB> But is there more data at the outer rim of the disc than at the inner
 HB> rim? 
Yes.  However, not all CD's go right out to the edge, as they're shorter
than 74 minutes.  Care should always be taken in handling them to
prevent damage and fingerprints anyway.
See ya, Cameron Hall
cameron.hall@bluebeam.gryn.org | ad121@freenet.hamilton.on.ca
Blue Beam BBS | 905 662 5784 | Stoney Creek Ontario Canada | v34 vFC FAX
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