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From: klein@ucbcad.UUCP
Newsgroups: net.audio
Subject: Cassette Head Alignment
Message-ID: <161@ucbcad.UUCP>
Date: Wed, 27-Mar-85 11:47:23 EST
Article-I.D.: ucbcad.161
Posted: Wed Mar 27 11:47:23 1985
Date-Received: Thu, 28-Mar-85 02:46:19 EST
Distribution: net
Organization: UC Berkeley CAD Group, Berkeley, CA
Lines: 54

A while back there was a discussion about cassette decks and head alignment.
Someone mentioned that Nakamichi was the only manufacturer to align them
right.  A friend of mine has an older Nak deck that I have used on occasion
to record albums.  I also have an auto-reverse car cassette deck, which
works by reversing the direction of the tape and switching its input
to the other pair of gaps in the head.

What I have noticed, only with the tapes recorded on the Nak, is that
one play direction always sounds much better than the other.  I have tried
to align the angle of the car deck's head to sound better (it was definitely
out of alignment from day 1).  It is easy to do this while the tape is running,
as there is a cutout that exposes the adjustment screw.  The result
is that I can never get both directions to sound good.

This implies to me that the Nak deck's head angle is not perfectly perpendicular
to the tape.  If it were, I would be able to align the car deck's head
perpendicular to the tape and both directions would sound fine.  This is
because while recording on the Nak you must physically flip the tape over,
so any leaning of the record head is reversed on the other side.  The
tape will look like this:

----------------------------------------------------
\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\
////////////////////////////////////////////////////
\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\
////////////////////////////////////////////////////
----------------------------------------------------

If I align the car deck's play head to sound good for one direction
of the Nak's tape, it will expect a tape that looks like this:

----------------------------------------------------
////////////////////////////////////////////////////
////////////////////////////////////////////////////
////////////////////////////////////////////////////
////////////////////////////////////////////////////
----------------------------------------------------

When it switches direction without physically flipping the tape, the
signal read is the integral of infinitely many signals all out of phase.
At certain frequencies, response (ideally) will go to zero.
This sounds really bad.  This problem does not seem to occur with
commercially prerecorded tapes, although they are not of the same
quality as the home-recorded ones and it is difficult to compare.

After all this, what is the problem?  Is the Nak correctly aligned
and does that mean that auto-reverse decks are no good?  Or does
it mean that this particular Nak deck is very poorly aligned?
Or something else?
-- 

		-Mike Klein
		...!ucbvax!ucbmerlin:klein	(UUCP)
		klein%ucbmerlin@berkeley	(ARPA)