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Path: utzoo!watmath!watcgl!dmmartindale
From: dmmartindale@watcgl.UUCP (Dave Martindale)
Newsgroups: net.audio
Subject: Re: Bias Adjustment in Cassette Decks
Message-ID: <2295@watcgl.UUCP>
Date: Thu, 22-Mar-84 13:27:36 EST
Article-I.D.: watcgl.2295
Posted: Thu Mar 22 13:27:36 1984
Date-Received: Fri, 23-Mar-84 08:13:57 EST
References: <6062@umcp-cs.UUCP>
Organization: U of Waterloo, Ontario
Lines: 25

When adjusting bias by ear, I would say do it with Dolby off.

There are three adjustments (at least) that must be made to adjust a deck
properly for a particular tape formulation: bias, record EQ, and record
level.  With a user-adjustable bias control, you can get only one of those,
so results won't be ideal.  If the record level is misadjusted, you will
inevitably get Dolby mistracking, as the Dolby circuits will read the
same signal as being at different levels on record and playback, and apply
differing amounts of high-frequency boost/compression.  With Dolby switched
off, at least you will be dealing with only bias-related frequency
response changes.

Note that setting bias by perceived frequency response won't get you
the best possible bias either, unless the record EQ just happens to be
correct for that tape.  The normal procedure for setting up a deck in
the shop seems to be to set the bias to produce some specified level of
distortion (that the manufacturer has found to produce the best tradeoff
of various problems), then set the record EQ so the frequency response
is flat, and then set the record level so that a given signal level into
the tape will produce the same level coming off, as seen by the level
meters and Dolby circuitry.

Without setting all three, you just won't get the best the deck is
capable of.  Is recording on many different varieties of tape that
important?