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Topic: Dbx (noise reduction)

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	Noise reduction - Wikipedia, the free encyclopedia
		Noise reduction is the process of removing noise from a signal.
		Noise reduction techniques are conceptually very similar regardless of the signal being processed, however a priori knowledge of the characteristics of an expected signal can mean the implementations of these techniques vary greatly depending on the type of signal.
		Dbx was the competing analog noise reduction system developed by dbx laboratories.
	en.wikipedia.org /wiki/Noise_reduction (822 words)

	Dbx (noise reduction) - Wikipedia, the free encyclopedia
		dbx did not achieve widespread popularity in the consumer marketplace, as compressed recordings did not sound acceptable played back on non-dbx equipment; Dolby B was already widely used when dbx was introduced, and its use of preemphasis gave far more acceptable results when played back on non-Dolby equipment.
		However, dbx was widely adopted in professional recording, and dbx Type II was used by Tascam in their Portastudio four-track cassette recorder for home studios, becoming standard on four-track cassette recorders of this type.
		An advantage of dbx compared to Dolby noise reduction is that it did not require calibration with the output level of the tape deck, which could cause incorrect tracking with Dolby B and C, leading to muffled high tones.
	en.wikipedia.org /wiki/Dbx_(noise_reduction) (532 words)

	Noise Reduction Systems - audiotools.com.
		We start seeing attempts of noise reduction using simple compander circuits as early as the 1920's although these were not intended to help with recording but rather to be used with phone lines (and vocoders were created to tackle the same problem).
		dbx corp. is manufacturing the 2 channel 929, it's a simple but fairy effective unit that only has filter controls, designed to fit into a dbx modular rack unit but can be used independently from that, it has internally switchable balanced/unbalanced outputs.
		A noise reduction and dynamic expansion system for records, basically a record was encoded with a system similar to a type II when mastered and decoded with a separate box hooked up to your hi-fi.
	audiotools.com /noise.html (1534 words)

	dbx noise reduction and digital ripping - Hydrogenaudio Forums
		The reason those dbx units were useful is because tape has a fixed noise floor, which means the noise becomes audible during quiet passages and is actually too low in loud passages (from an efficiency point of view).
		The key to their noise reduction system (as best I remember it) was that the zero gain point was dynamic, and shifted based on the content of the signal - there was a fancy, patented RMS level detection circuit which controlled the VCAs which actually did the compression or expansion.
		The difference between dbx Type I (professional) and Type II (consumer) noise reduction was the shape of the filtering applied to the signal in the analog computer chain.
	www.hydrogenaudio.org /forums/index.php?showtopic=27666 (1287 words)

	Mailgate: rec.audio.tech: Re: DBX "simultaneous encode/decode" noise reduction (Site not responding. Last check: 2007-11-07)
		Mailgate: rec.audio.tech: Re: DBX "simultaneous encode/decode" noise reduction
		It was possible to reduce some noise on LP's and Tapes without pre-encoding, though obviously actually using an encoding scheme would be much more preferable.
		IOW, that these > units could be used function as single ended noise reduction, that the tape > output of the unit would be dbx processed (compressed and then expanded, > 2:1, so that noise is decreased on the fly).
	mailgate.supereva.it /rec/rec.audio.tech/msg41711.html (189 words)

	TVTechnology - Inside Audio
		Keep in mind that those noise reduction numbers are simplifications of what is really going on, but they are the primary numbers used to describe noise reduction performance by marketing departments (you might want to read the section on "The Meaning of Specs" in my book "Total Recording" for more information on this).
		Interestingly, and not coincidentally, Dolby C was advertised as yielding 20 dB of noise reduction.
		Then go to the noise reduction pages (www.dolby.com/tech/#head4) and wade through Ken Gundry's series of pieces on the principles of noise reduction (www.dolby.com/ken/), aka "Ken's Corner." You may learn far more than you want to know about noise reduction, but this is a really useful primer for a difficult subject.
	www.tvtechnology.com /features/Inside-Audio/f-DM-dolby-07.10.02.shtml (944 words)

	Noise Reduction (Site not responding. Last check: 2007-11-07)
		If the noise is not masked by loud passages then one may hear the compander “pumping” or “breathing”.
		So the noise of a two track recording is 3 db higher than that of a mono recording, while the inherent noise of four tracks is 3 db higher than two, and so on.
		Luckily there are very effective noise reduction techniques available for use with analog tape which rival the signal to noise specifications of digital recordings.
	www.sfu.ca /sca/Manuals/ZAAPf/n/noise_reduction.html (303 words)

	Noise Reduction in Tape Recording
		A persistent random noise signal from the residual magnetization of the oxide granules limits the fidelity of magnetic tape recording.
		Fortunately, noise reduction schemes such as Dolby and dbx can discriminate against this tape hiss to provide higher fidelity tape recordings.
		The dbx system is an compression-expansion scheme for increasing dynamic range and for decreasing tape hiss.
	230nsc1.phy-astr.gsu.edu /hbase/audio/tape4.html (374 words)

	Noise Reduction in Tape Recording
		The fidelity of a tape recording is limited by "tape hiss", high frequency random noise resulting from the fact that the magnetizations of the oxide particles of the magnetic emulsion do not add to exactly zero even in the absence of a recorded signal.
		Noise reduction systems like the Dolby and dbx systems help to overcome this by pre-emphasis of high frequency, low-intensity music signals upon recording so that they, along with the tape hiss, can be de-emphasized upon playback.
		Because of the small size and close spacing of the granules, the noise is of high frequency and is descriptively called "tape hiss".
	hyperphysics.phy-astr.gsu.edu /hbase/audio/tape4.html (374 words)

	BACKGROUND NOISE IN VIDEO HI-FI
		To reduce this system noise below the level of audibility and expand the system's dynamic range, the manufacturers use a complex noise-reduction system, the essential operating principle of which is to compress the volume levels during recording and restore the original volume levels during playback.
		Instead of going to the added expense of a DBX designed system, the manufacturers used their own noise-reduction systems which do not solve the problems of this recording system as well as is needed.
		Evidently subsonic noise is one of the things that trigger the compressor-expander in the noise-reduction device, causing it to raise the whole background level to the point where it causes those obtrusive sounds.
	www.anstendig.org /VCRNoise.html (2120 words)

	Dbx Compressor (Site not responding. Last check: 2007-11-07)
		The original company goal was: ''"To get closer to the realism of a live performance."'' dbx is best known for the DBX noise reduction system.
		dbx is a noise reduction system for analog tape recording and North American TV broadcasting.
		Dbx type 1 compresses the recording by a 2:1 ratio.
	www.wwwtln.com /finance/59/dbx-compressor.html (523 words)

	David Blackmer The industry mourns the passing of the innovative man who founded both dbx and Earthworks (Site not responding. Last check: 2007-11-07)
		In 1971 David founded dbx, the company, and invented dbx, the noise reduction system.
		"The idea behind dbx was based on the idea of using decibel expansion to replace the peaks lost to the limited dynamic range of magnetic tape," continues Eric Blackmer.
		dbx's initial offering, the classic 160 compressor/limiter, quickly became a studio standard.
	www.earthworksaudio.com /f_reviews/eqmag/eqmag_dblackmer.html (501 words)

	Mailgate: rec.audio.tech: Re: DBX "simultaneous encode/decode" noise reduction (Site not responding. Last check: 2007-11-07)
		On the > simpler dBx systems (117,118, 119, 1Bx) more serious problems could ensue, > as a kind of 'breathing', which is due to modulation of either HF material, > or hiss, by LF material on the source.
		Thanks, > > James > > You COULD use one of the single ended noise reduction** systems (as a double > ended unit), but you would need to pay careful attention to the record > levels.
		These all are "simultaneous encode/decode" systems, so that the signal coming out of the outputs on the dbx unit is simultaneously compressed and then expanded.
	mailgate.supereva.it /rec/rec.audio.tech/msg41713.html (542 words)

	MIC: Glossary of Preservation Terms
		Noise reduction (Dolby A, B or C, dbx Type I or II) may be used.
		Noise reduction (Dolby A or B, dbx Type I) may be used.
		Most systems (Dolby and dbx) are double-ended, meaning that a recording is encoded with a particular noise reduction type and must be played through a compatible decoder to return accurate reproduction.
	mic.imtc.gatech.edu /presglos_1.htm (5774 words)

	AudioReview.com - Technics RS-1500US Reviews
		The Dbx type 1 noise reduction unit was designed with open reel decks in mind.
		The midrange and treble are fine,and free of grit,and glare.
		The DBX noise reduction is a great compliment here,and I can't see making a great recording without it.
	www.audioreview.com /mfr/technics/tape-decks/PRD_121191_1595crx.aspx (802 words)

	Modulation Sciences Inc. (Site not responding. Last check: 2007-11-07)
		A sync lockable subcarrier generator, dbx noise reduction encoding, audio processing, and peak deviation meter are all integrated into one box.
		A wideband noise source and AM detector are also provided for tuning the aural transmitter system for minimum synchronous AM.
		Noise reduction encoding employing the dbx noise reduction system that won the approval of the EIA's (now the CEA's) Multichannel Sound Committee.
	www.modsci.com /products/televisionProducts/tsca189/details.asp (349 words)

	DJzone DJ Information Portal (Site not responding. Last check: 2007-11-07)
		Of course this defeated the noise reduction aspect of it, but many users liked the high-end boost as well as the smooth high frequency tape saturation on their tapes.
		Dolby S-type noise reduction was derived from Dolby SR, and shares with it such developments as combining both fixed and sliding bands, anti-saturation, spectral skewing and modulation control.
		Not only was it designed to provide more noise reduction than past systems, but it also provided a number of other technological innovations that extend the recording's dynamic range and allowed a very high quality master recording (very nearly digital).
	djzone.com /pg/gloss/djd.shtml (6285 words)

	dbx History (Site not responding. Last check: 2007-11-07)
		dbx tape noise reduction systems used in professional recording studios around the world.
		dbx manufactured signal prosessing equipment only, until the company became a part of the BSR group in 1979.
		The dbx consumer line ends in 1989, when the BSR leader Sanju Chiba aquired BSR, changed its name to ELP, and sold out the dbx business.
	www.audioinvest.no /dbx/dbx_hist.htm (139 words)

	Ultimate Multitrack Analog to Digital Transfers - Sonicraft A2DX Lab (Site not responding. Last check: 2007-11-07)
		But, in discussing these noise reduction systems, there's an important point to be made about proper decoding of tapes using them.
		So, the first priority in noise reduction decoding must be accurate playback from the analog tape machine.
		So, while the tape could store a signal that is very true to what the noise reduction encoder delivered, on a less than optimal playback machine, deficiencies and/or anomalies in playback response could present the noise reduction decoder with significant differences in the signal.
	www.sonicraft.com /a2dx.html (2953 words)

	STUDIO SOS (Site not responding. Last check: 2007-11-07)
		The Dbx noise reduction system was relatively simple in comparison and, although not so widely used in professional circles, was adopted readily in the semi-pro markets.
		When Dbx noise reduction is being used, it is generally wise to err on the side of caution when setting levels.
		When Paul expressed the view that the Dbx noise reduction on my Tascam 388 was a fairly unsubtle system, and that it might well be having an adverse effect on my recordings, it confirmed my own suspicions, and it has hardened my resolve to acquire a stand-alone hard disk recorder.
	www.soundonsound.com /sos/Oct02/articles/studiosos1002.asp (4669 words)

	Stereophile: What Makes a Good Recording?
		Tape hiss, for which there is little excuse in these days of effective noise reduction (dbx, for example), can be raised from an almost-subliminal rushing to an irksome hissing by upper-range frequency-response peaks in the transducers.
		Some environmental noise is almost inevitable in any recording made before an audience, but tends to be less distracting to a listener familiar with the live-performance experience than to one who listens mainly to studio-made recordings.
		It is quite possible to tape-record, without noise reduction, the full dynamic range of a large orchestra, but some hiss will be audible at listening levels approaching the originals.
	www.stereophile.com /asweseeit/122/index3.html (818 words)

	Home Recording dot com BBS - DBX Noise Reduction with Digital? (Site not responding. Last check: 2007-11-07)
		Additionally, if I am not mistaken, the DBX noise reduction units do not use compression in any form, so you would not be decreasing the dynamic range in the music any.
		The way I understand the DBX process is that it compresses (the encoding part) and then expands (the decoding part) signal.
		As Track Rat said, the DBX stuff has a problem with artifacts at the crossover threshold of being on/off, so they would actually introduce MORE noise into the signal at a much higher level than any quantization noise.
	homerecording.com /bbs/showthread.php?t=40672 (1263 words)

	Home Recording dot com BBS - dbx noise reduction
		Sounds to me like you might be recording with the dbx off and playing back with it on.
		I just started renting a tascam 488 and had the same trouble: i would record w/out the dbx and then turn it on during playback, and it would do this weird kind of doppler effect kind of thing, which is probably what you are calling getting real soft and then real loud.
		I always left the DBX on and never had any problem with it humming or fading.
	homerecording.com /bbs/showthread.php?t=14317 (230 words)

	Audio Recording Studio Equipment For Sale
		DBX 150 type I noise reduction system rack mountable each unit taking 1 u space.
		The caveat of using a "compander" type noise reduction system due to "pumping and breathing", modulation noise is not an issue here.
		Types "B" and "C," the dbx noise reduction system is implemented across the audio spectrum.
	www.mindoverdata.com /classifieds.htm (449 words)

	eBay - dbx noise system, Pro Audio, Home Audio items on eBay.com (Site not responding. Last check: 2007-11-07)
		DBX 150X Type 1 Noise Reduction System (used)
		DBX Model 224 Type II Noise Reduction System
		DBX 158 Modular Noise Reduction System DBX 410
	search-desc.ebay.com /search/search.dll?query=dbx+noise+system&... (280 words)

	Noise reduction tips from NSS
		This probably might not cause a large problem, but may induce some noise, especially if the input connector is not a balanced one (many are not).
		We do not recommend using dbx on your mastering deck unless you are sure that your audience has dbx decoding (which many do not have).
		dbx is a trademark of dbx which is a sub.
	www.ram.org /music/making/tips/nss_nr_help.html (816 words)

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