Path: utzoo!attcan!uunet!decwrl!wuarchive!zaphod.mps.ohio-state.edu!uwm.edu!csd4.csd.uwm.edu!info-high-audio-request
From: drm2@mvuxn.att.com (David R Moran)
Newsgroups: rec.audio.high-end
Subject: Re: dbx
Message-ID: <6554@uwm.edu>
Date: 24 Sep 90 12:48:06 GMT
Sender: news@uwm.edu
Lines: 61
Approved: tjk@csd4.csd.uwm.edu

In article <6446@uwm.edu>, tomp@vicom.com (Tom Pohorsky) writes:
> In article <6421@uwm.edu> 09nilles%cuavax.dnet@netcon.cua.edu (Fiver Toadflax) writes:
> >>Anyone out there in "netland" using DBX on a cassette deck?  What do you
> >>think of it?
> >
> >I have it both as a seperate component and as part of my tape deck.
> 
> What I was told a while back, and I still believe to be true is:
> There are basically two types or grades of DBX Noise-reduction circuitry.
> The better kind one finds in the 22x outboard boxes, and uses a higher
> voltage (9 ?).  The type put inboard into cassette decks runs off a
> lower voltage, and the record-mode (compression) fidelity is not quite
> as good. Playbacks are virtually the same.
> 
> Any one have any more on this ??  Allegedly the data sheet specs indicate
> this "lower" performance, but I don't have access to them.
> 
> 
> -- 
> ames!vsi1!tomp      tomp@vicom.com


dbx comes in two flavors, type I and type II. The former is for
better media (e.g., tape decks > 15 ips) and goes slightly 
lower in the bass (to the octave below 40 Hz). Type II is more
forgiving and was designed for cassettes, encoded LPs, video tape
(NOT with HiFi audio, though, which is similar to type II in the 
first place, wrapped around FM), 7.5 ips open-reel etc..... I and II
are not compatible, having different preemphasis and deemphasis
curves. II is highpassed at around 40-30 Hz.


Type II in cassette decks is not always up to the standard of outboard
dbx-manufactured II boxes, as in 228, 224, and other model numbers for
that family. But it often is; the chips are good and uniform for the
most part. Some cassette deck manufacturers implement things with care,
some with less care, same with Dolby; there is no safe generalization.
Sonically the difference with so-called inferior chip sets and noisy
stages and loose-tolerance preemph/deemph is still going to be very
small.

So I would not sweat it much. Compared with how cassettes fail in 
wow and flutter, scrape noise, noise-floor modulation, azimuth
consistency, plus al the bias and EQ headaches, etc. etc. etc. 
(it's a loathsome
medium, really, requiring tremendous compensatory engineering), NR
is not usually the salient problem to my ear. Although Dolby can be fussy.

With dbx, just keep your levels high and hit the tape hard.

One advantage with outboard dbx is that you can wrap it around cassette
with Dolby B, which helps....

dbx sonically is just fine for everything but sharp events where the
harmonics are not loud enough to mask successfully. Piano, especially
low-level piano, bongos, wood blocks, sometimes plucked bass, 
baseball bats, and the like all may reproduce with noise tails that
are the sound of the tape noise floor being modulated by the companding.
The better the S/N the lesser the problem. With other material, from
rock to choral to orchestral to flute, no prob, and usually good results.
And very very very quiet.