* "Michael Graves" <[EMAIL PROTECTED]> on Sun, 03 Jun 2001
| DDS-2 and -3 are both rotory head
"helical scan"
| recording schemes not unlike common VCRs.
Exactly like common VCRs and camcorders.
| That said what we need concern ourselves with is the linear speed of the
| head movement cross the tape, not the running speed of the tape past the
| head drum which is a secondary issue. [...]
Sort of.
Say, for example, a helical scan mechanism that writes 1cm wide tracks on
the tape, and it takes 1 second for the head to make one full rotation.
The linear mechanism must move the tape 1cm every full rotation of the
head, or 1cm/s. If you increase the rotational speed to 2 rotations per
second but do not change anything else, you can get overlapping tracks,
which is bad.
DLT adds more write heads and makes them smaller (but DLT is a linear type
mechanism, not helical scan). DDS/DAT makes the heads smaller and spins
them faster to make use of that.
If the tracks are now 0.25cm wide, with rotational speed 4 times that of
the basic media, you get 4 times the data density on the same length of
tape. But as I said originally, it is head size that is the primary
factor, not speed.
| Early digital audio at the studio production level added some other
| issues. There was for a time non-rotory head multi-track audio recorders
| which employed a head stack with a large number of head gaps, each
| writing a bit such that the data was written to tape in a parallel
| fashion.
You mean like 8-track :).
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