Path: utzoo!attcan!uunet!wuarchive!usc!zaphod.mps.ohio-state.edu!uakari.primate.wisc.edu!dali.cs.montana.edu!milton!ogicse!cvedc!gssc!jdm
From: jdm@gssc.UUCP (John David Miller)
Newsgroups: comp.music
Subject: Re^2: dbx vs. Dolby C Noise Reduction
Message-ID: <6278@gssc.UUCP>
Date: 23 Jul 90 16:15:40 GMT
References: <590@lexicon.com> <1920003@hpcuhc.HP.COM>
Organization: Graphic Software Systems,  Bvtn OR
Lines: 34

edwardm@hpcuhc.HP.COM (Edward McClanahan) writes:
>...Older DBX units were
>subject to a condition known as "pumping", basically a result of not being
>able to accurately decide (based on the signal) when to emphasize and when
>to de-emphasize....

Yes, this is very true.  There are several "types" of dbx noise reduction,
most of which fall into the encode/decode catagory.  I don't know all of the
types, but studio gear typically uses Type 1, while newer cassette decks with
built-in dbx (TEAC, Onkyo, et al) use Type 2.  For all I know, they may in
fact be the same thing calibrated for different use.  I do know that Type 1
is *very* good, and you'd be hard pressed to find any pumping.  (That CD
you're listening to was probably made from a Type 1 encoded multi-track tape, 
unless it is an all-digital recording.)  I think the improvements can be
attributed to advances in circuit speed and dividing the frequency spectrum 
into separate NR bands.

In the studio, variable compression/expansion units (made by dbx, Symetrix,
et al) are a way of life.  Even all-digital recordings can't handle the full
dynamic range of many instruments....

One final note: a $250 piece of gear that will make your ho-hum CD's, LP's,
cassettes, etc. COME ALIVE - the BBE 422a Sonic Maximizer.  This is one
AMAZING piece of signal processing machinery in a 1U rack space.  Check it
out at music stores that cater to the studio crowd.  Testamonial: I just 
bought over $10k of studio stuff, and this piece pulls its weight more 
than any other.  

-- jdm
-- 
John David Miller                      jdm@gss.com
Graphic Software Systems               uunet!gssc!jdm
9590 S.W. Gemini Dr.                   (503) 641-2200 (voice)
Beaverton, OR  97005-7161              (503) 643-8642 (FAX)