Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Posting-Version: version B 2.10.1 exptools 1/6/84; site ihu1g.UUCP
Path: utzoo!linus!philabs!seismo!harpo!ihnp4!ihu1g!fish
From: fish@ihu1g.UUCP (Bob Fishell)
Newsgroups: net.audio
Subject: Re: NX 40 ...
Message-ID: <140@ihu1g.UUCP>
Date: Fri, 13-Jan-84 16:46:45 EST
Article-I.D.: ihu1g.140
Posted: Fri Jan 13 16:46:45 1984
Date-Received: Sat, 14-Jan-84 23:57:19 EST
References: <65@whuxj.UUCP>, <2204@allegra.UUCP>
Organization: AT&T Bell Labs, Naperville, IL
Lines: 40

I can't speak for the NX-40, but I shall once again write in praise of the
dbx model 224 nr system.  I have been using it for about 3 1/2 years now, on
a wide selection of music including solo piano works.  I have discovered no
pump-wheeze noise problems, no residual hiss (what there is is below the
noise floor of my amplifier), in short, no audible trouble AT ALL, on any
type of recorded material.  Of course, I use it with an open reel deck,
not with cassettes.  Maybe that's part of the difference; open-reel tape
is much quieter than cassettes when no noise reduction is used.

I must reiterate: dbx provides calibration instructions with their units which
must be followed carefully.  I think some of the problems folks are having out
there are related to improper calibration.

dbx works by applying 2:1 (dB) compression to the input signal, along with
preemphasis of the high frequencies.  One thing this does is tax the high
frequency response characteristics of the recorder and the tape used.
Again, open reel decks are far better than cassettes in this category.
The best specs I have ever seen on a cassette deck ran into something like
19kHz on the high end.  Open reel decks recording at 7 1/2 ips typically
go up to 24kHz.  This response difference could also be a source of
problems for dbx users with cassette decks.  Unless one of the better
decks is used, with metal tape, some of the information in the original
input signal could get squeezed out by the compression and preemphasis.
The result on playback would be distortion and a loss of high frequency
harmonics.  This would be especially noticable on piano music, where 
harmonic content and purity are the key to good reproduction.

I have found Dolby C and metal tape (I have the Harmon-Kardon CD201 deck)
to be perfectly adequate for many types of recording, but I can notice a
difference in the clarity and definition of the sound.  I always know I'm
listening to a tape with the cassette deck, but the dbx-encoded reels sound
considerably more like the originals they're made from.

Cassettes are compact and convenient, but I don't believe that they will ever
match the quality one can get with open reels.  Furthermore, I think that 
dbx is probably best suited for open reel applications; cassette deck owners
should be content with Dolby.  It's not perfect, but it's pretty good, and
it's economical.

                             Bob Fishell