jdm@gssc.UUCP (John David Miller) (07/23/90)
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)
scott@bbxsda.UUCP (Scott Amspoker) (07/24/90)
In article <6278@gssc.UUCP> jdm@gssc.UUCP (John David Miller) writes: > 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. As I understand it, Type 2 DBX (designed for home use) is not as sensitive to the higher frequencies as Type 1. This supposedly compensates for the tendency of consumer models to lose a little high end over time. Therefore, if the high end degraded a little the decoder would still function properly. -- Scott Amspoker Basis International, Albuquerque, NM (505) 345-5232 unmvax.cs.unm.edu!bbx!bbxsda!scott
paul@kuhub.cc.ukans.edu (07/24/90)
> 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. According to dbx literature dbx I uses a different pre-emphasis/de-emphasis. In addition, dbx II uses the audio spectrum between approximately 50 Hz- 10 kHz to determine the RMS level of the signal to compensate for the possible high frequency "drop off" in the frequency response of cassette recorders and the head-contour effect on the bass frequencies of most cassette recorders.
darenm@hpnmdla.HP.COM (Daren McClearnon) (07/24/90)
Unfortunately, DBX as a company abandoned the dbx noise reduction market at the first blush of the compact disc era, say 7 or 8 years ago. I always preferred dbx for consumer rock recording but could never find car stereo equipment or friends with dbx to make it practical. Nowadays, if you read the litany on Dolby SR, it is basically doing multi-band, bandlimited compansion like you always hoped dbx would do some day. But no, they diversified into speakers and components and are not even doing DSP versions of their older signal processing stalwarts like the 4BX. One complaint I've had with dbx is that the high-frequency pre-emphasis usually saturates non-metal tape at higher record levels; they really should have created the equivalent of Dolby HX, which modulates the bias, or Tandbarg's Dyneq, which modulates the equalization, as a function of record level. ALL IN ALL - dbx:audio::beta:video |\/\/\/| | | /----------------\ | | | COWABUNGA, DUDE. | | (o)(o) /,----------------/ C _) | ,___| | / /____\ / \ Daren McClearnon somewhere in Hewlett Packard.