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From: fish@ihu1h.UUCP (Bob Fishell)
Newsgroups: net.audio
Subject: Re: Consumer Reports and dbx
Message-ID: <246@ihu1h.UUCP>
Date: Wed, 6-Jun-84 11:34:54 EDT
Article-I.D.: ihu1h.246
Posted: Wed Jun  6 11:34:54 1984
Date-Received: Thu, 7-Jun-84 07:49:27 EDT
References: <268@whuxj.UUCP>
Organization: AT&T Bell Labs, Naperville, IL
Lines: 33


(oo)

>I certainly agree with their recommendation for noise reduction.  They believe
>that dbx is the most effective means of noise reduction, and recommend the
>use of an outboard dbx 224 if your tape deck doesn't have built-in dbx.
>Bill Mitchell (whuxj!wjm)

I'll go along with this, too, but with a caveat.  dbx noise reduction works
by preemphasizing the high frequencies and compressing the program dynamics
on the encoding pass, and by reversing both processes on the decoding
pass.  The result is dead silence where no recorded signal is present, 
something Dolby does not quite achieve.  However, the encoding process tends
to tax the high frequency capacities of the tape and deck.  This is no problem
for open reel decks or for certain high-quality cassette decks, which have
a frequency response well in excess of the limits of human hearing.  However,
use of dbx without a deck and tape capable of extended high-frequency response
will result in an unpleasant "pumping" sound.

I use a dbx 224 with my open-reel deck, but I've found that Dolby C is
perfectly adequate for cassette recording.  Dolby does not give you
the headroom that dbx does for, say, recording from compact discs,
but is probably better suited to the cassette medium.  Besides, dbx-encoded
tapes sound awfully funny when played back without decoding.  Some auto
tape players are now available with dbx, but most only have Dolby B, if
anything at all.  Dolby C is compatible for playback on Dolby B (it isn't
linear, but it doesn't sound too bad), but dbx isn't.  In short, dbx is
better, but not as flexible.

-- 

                               Bob Fishell
                               ihnp4!ihu1g!fish