And so it came to pass, on 08-17-96 08:58,
   that Herry Budiutama spake unto Cameron Hall:
 HB> Btw, what is the difference between 3-head and other units?  How
 HB> many heads are there usually on a tape deck?  I thought there was
 HB> only 1 head, 1 tape eraser, 2 capstans for auto-reverse decks, and
 HB> 2 pinch rollers.
On most "cheaper" decks (cassette and open-reel), a single head or head-gap 
does doule-duty for both record and playback.  This requires a compromise, 
though -- to get the optimum signal stregth on the tape, a record head's gap 
should be relatively large.  However, the smaller the head gap, the better 
the high-frequency response you get on playback.  So the width of the gap on 
a standard R/P head is a careful balance between the two needs.
In cassette decks, a "three-head" design usually still only has one physical 
head for record and playback, but internally that block has two separate head 
gaps, one optimized for record, the other for playback.  The tape path would, 
in all instances except one where the designer was on drugs, cross the record 
head gap, then the playback head gap.  This has the added advantage of 
letting you listen back to the recording *from the tape*, the instant after 
it's been made.  It makes calibration of head alignment, metering, bias, etc. 
much easier.
Larger open-reel decks (such as the big 1" and 2" multitracks) will actually 
have separate physical headblocks for record an playback; this provides for 
no interference between the two coils, and allows them to be aligned and, 
when necessary, serviced or replaced separately.  There's also a slight time 
delay between them (although it's minimal, since the tape is generally moving 
15-30ips), which can be used to create some pretty weird effects :-)
  >> Can't help ya with the Dolby S.  My deck is an AIWA ADF-990.  Still
  >> records a mean signal on any brand of tape too, well... except for
  >> Ferri-chrome..., but that stuff didn't last long. :-)
 HB> Mine is a Sony TCWE605S.   It also got this auto record level
 HB> function that tests the maximum record level automatically
 HB> according to the type of tape you insert (Type I, Type II or Type
 HB> IV -  what happenned to type III ?)
Ferrichrome *was* "Type III".  I've actually seen one or two high-end decks 
that had a setting for it, but good luck ever actually finding the stuff.  I 
guess it just never really caught on...
Type I is "Normal" tape, the coating of which is composed of ferric (iron) 
oxide -- in short, rust.
Type II is the so-called "Chrome" tape, really chromium dioxide (CrO2) -- 
techncially, oxidized (rusted) chrome :)
Type IV, or "Metal" tapes, use pure (ie. unoxidized) metal particles.
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Q: Why don't blind people skydive?
A: It scares the heck outta their dogs!
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