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CX (noise reduction)

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The CX logo, present on LPs and laserdiscs utilizing CX noise reduction

CX is a noise reduction system for recorded analog audio. It was developed by CBS Laboratories (a division of CBS) in the late 1970s as a low-cost competitor to other noise reduction (NR) systems such as dbx disc and High-Com II, and was officially introduced in 1981.[1][2][3][4] The name CX was derived from "Compatible eXpansion", a feature of the technique.[4]

Use on vinyl LP records

[edit]

CX was originally designed by CBS as a noise-reduction technology for vinyl LP records,[5][4] similar to the earlier dbx disc (based on dbx II) and High-Com II systems, but, like the later UC system, it aimed at the lower-cost consumer mass market rather than high-end audiophile niche markets only. CX-encoded records required a special CX expander connected to a stereo system, in order to fully reproduce the CX encoded sound on the LP. However, in contrast to dbx disc and High-Com II, CX-encoded records, like UC-encoded records, could also be played without a decoder with a resulting (claimed acceptable) amount of dynamic range compression.[6][4] CX being a 2:1:2 compander system, a noise reduction of 20 dB(A) was achieved for a resulting maximum dynamic range of typically 80 to 85 dB(A) (other sources claiming up to 95 dB(A)[7] or even 107 dB[8]).[6] The theory of operation is described in U.S. patent 4,376,916.[9]

The project was led by CBS Records group vice president Bob Jamieson and carried out by a team led by Daniel W. Gravereaux[2][6] and Louis A. Abbagnaro.[6] The label predicted that CX encoding would become standard on all new LP releases, but this did not happen. CBS struggled to gain support for the system from other record companies. The process was controversial among CBS executives[4] and unpopular with some artists. Classical guitarist Liona Boyd demanded that the CX encoded version of one of her albums be withdrawn because of perceived shortcomings, even though Jamieson claimed that CBS had the technical means to overcome such objections.[10]

Based on an UREI reference design published by CBS,[11] many third-party builders of CX decoders used a dual operational transconductance amplifier 13700D made by JRC (today NJR),[12][13][14][15][16][11] coupled with a pair of quadruple JFET operational amplifier chips TL084 in their designs. Among them were Telefunken with their RN 100 CX, RS 120 CX[16] and RS 220 CX. The documented playback time constants of the decoders were slightly changed by CBS in 1981/1982.[11]

In 1982, the CX integrated circuit U2141B was developed by AEG-Telefunken, Germany, by Ernst F. Schröder, Dietrich Höppner and Kurt Hintzmann,[2] the same team who previously designed the High Com noise reduction system,[2][17] a broadband compander with up to 20 dB of noise reduction.[18][6] Hitachi also offered dedicated CX chips named HA12043 (for CX 14) and HA12044 (for CX 20) in 1983.[17][18][19]

Approximately 70 CX encoded LP titles were released by CBS up to 1983 in the United States.[4] Gasparo also released a number of CX encoded records.[4] In Europe, many CX discs were manufactured in the Netherlands with the catalog number prefix "CBSCX". The albums in this series also came in standard, non-CX encoded versions. A total of about 150 CX encoded titles exist.

The implementation of a software decoder for CX is under consideration.[20]

Use on LaserDisc and CED VideoDisc

[edit]
Back of a Laserdisc sleeve, noting the use of CX noise reduction.

While the implementation of CX with LPs was quite unsuccessful and short-lived, CX would later see success as the noise reduction used for the stereo analog audio tracks on the LaserDisc (LD) format. It was also used for the audio tracks on discs of the RCA SelectaVision CED Videodisc system.[citation needed]

All LaserDisc (and stereophonic CED) players manufactured since 1981, when the CX equipped LD-1100 was introduced, had CX noise reduction capability as a standard feature. Pioneer also released a stand-alone CX adapter R-1000[21] for use with their VP-1000, Magnavox's VH-8000/8005 and the industrial players that were all released before CX was adopted. The first CX encoded LaserDisc was Olivia Newton-John's Olivia Physical, released by MCA Videodisc.[citation needed]

CX decoders made for LPs could not be used with LDs because the CX companding specifications for LaserDisc were changed, from 20 dB of noise reduction to 14 dB, along with moving the 'threshold' where compression/expansion changes from 2:1 to 1:1 from −40 dB to −28 dB - other minor changes to the decoding time constants were made as well.[22] In addition, some of the LaserDisc's FM audio encoding specifications were modified too, allowing more headroom and better high frequency response at high levels. These changes were made because, at the time of CX's adoption on LaserDisc (1981), the vast majority of program sources used for mastering, such as 35 mm optical and magnetic film soundtracks, as well as the 2-inch IVC-9000 and the 1-inch C-Type videotape formats used for LaserDisc mastering, had signal-to-noise ratios low enough that undecoded playback would accentuate their noise to unacceptable levels.[citation needed]

By reducing the total amount of noise reduction and modifying other aspects of the CX system to better match LD's FM audio shortcomings, undecoded playback sound quality was maintained and vastly improved decoded sound was achieved at the same time. The possibility of audible pumping or breathing artifacts during CX decoded playback were reduced as well.[23]

While CX greatly improved the audio quality of LaserDisc's FM audio tracks, its primary reason for adoption was to decrease the amount of interference between the right channel's FM audio carrier and the video carrier's first chroma sideband. Without CX, strict filtering during mastering and playback as well as keeping color saturation below 75% on the master were required to keep any interference below −35 dB, which ensured that no beats or other artifacts were visible in the demodulated image. Although CX improved the picture quality, it was not normally used on discs with mono audio. Pioneer Video, the main manufacturer of LDs at the time, required the studios to request CX and, since most did not know that CX improved the video quality of the finished discs or the audio of mono titles, CX was rarely requested. Due to this lack of knowledge about CX at the studios, there were many stereo titles released without CX encoding and, in fact, CX didn't become standard on all LaserDisc titles until the late 1980s. A look at Pioneer's catalogs as late as 1987 shows that the majority of titles did not have CX encoded analog sound - most were not digital either.[original research?]

For the CED VideoDisc, since stereo was not added to the format until its second year on the market, RCA made CX a mandatory part of CED's stereo system - a disc could not be released in stereo without CX encoding - and the companding specifications were unchanged from those of the LP system due to the CED system's much higher noise levels than the LaserDisc format. Although RCA improved the plastic/carbon formulation used to make discs, which lowered disc noise levels by 3 dB, and modified the mastering system, the CED format still required the full 20 dB of noise reduction that was achieved with the unmodified LP system.[original research?]

The names given by CBS to the two different versions of CX were CX-20 and CX-14.[23][24]

Use in FM radio broadcasting

[edit]

CX was used in FMX, a commercially unsuccessful noise reduction system developed in the 1980s for FM broadcasting in the United States. FMX was intended to improve fringe area reception of FM stereo by adding a CX-encoded version of the L−R (left-minus-right, or difference) signal modulated in quadrature with the conventional stereo subcarrier. About 50 stations utilized the system, but few FMX-equipped receivers were manufactured, and after FMX was accused in 1989 of actually degrading reception rather than improving it, support dried up and the system was abandoned.

CX enabled equipment

[edit]

These devices are known to support CX:

  • Backes & Müller CX Decoder[6]
  • CBS CX Expander Model E-1016[3]
  • CBS Technology Center CX Compandor Model 9101
  • cm labs cm678 CX decoder[6]
  • Elektor CX decoders (DIY projects[25][26] based on the LM13700D/NE5517N[27][28][29] and HA12044[19])
  • Kort Elektronik Dynamik Expander + CX Decoder SR[30][6]
  • phase linear / aie CX Decoder Model 220[31]
  • Pioneer CX Decoder R-1000 (external CX 14 expander for LDs)[21]
  • Popular Electronics / Phoenix Systems CX decoder by John Roberts (DIY project based on the CA3280)[32][11][33]
  • Radio-Electronics CX decoder by Joel Cohen (DIY project based on the LM13700)[34]
  • Soundcraftsmen Preamplifier Model CX4000
  • Soundcraftsmen Differential/Comparator Preamp-Equalizer Model CX4100
  • Soundcraftsmen Differential/Comparator Preamp/Equalizer Model CX4200
  • Telefunken RN 100 CX (external phono preamp with CX decoder based on LM13700)[35][6][36]
  • Telefunken RS 120 CX (belt-drive record player with built-in preamp and CX decoder based on the NJM13700D)[16][6]
  • Telefunken RS 220 CX (direct drive record player with built-in preamp and CX decoder)[16][6]
  • Thorens PCX 975 by Heribert Heise (external phone preamp with CX decoder, claiming a dynamic range of up to 107 dB)[8][6]
  • UREI CX Mastering Encoder/Decoder Model 1181 (switchable compander for CX 14 and CX 20 with half-speed mastering option based on Allison Research EGC-101, claiming a dynamic range of up to 95 dB(A))[7][37]
  • CX decoder by Markus Holtwiesche (DIY project based on the HA12044)[38][39]

CX encoded vinyl records

[edit]

The following vinyl records are known to have been produced in CX encoded editions:[6]

See also

[edit]

References

[edit]
  1. ^ Fantel, Hans (1981-07-12). "CBS Improves the Standard LP disk". Sound. The New York Times. p. section 2: 21. Archived from the original on 2021-05-03. Retrieved 2021-05-04.
  2. ^ Jump up to: a b c d Schröder, Ernst F. (2009) [2007]. "The Story of HIGH COM". Archived from the original on 2016-04-16. Retrieved 2016-04-16. […] in autumn of 1981, CBS in the U.S. introduced a compander for vinyl records, the CX-system […] From January 1982 on I developed an integrated circuit for the CX compander in collaboration with the designers in the AEG-Telefunken, semiconductor factory. From 5 to 9 April 1982 I went to CBS in Connecticut to get the finished circuit (U2141B) tested there. I was well received at the hotel, but was then held there for a day because of a severe snow storm. All the traffic and all public activities had stopped. The following day then I met Dan Graveraux, head of the CX development team at CBS. In a pleasant atmosphere we tested the circuit and I won the coveted OK. This time my work was paid for by the AEG-Telefunken semiconductor factory in Heilbronn. […] [1]
  3. ^ Jump up to: a b Handbook CX Low Cost Expander Model E-1016 (revised ed.). Stamford, Connecticut, USA: CBS Technology Center. 1981-08-02.
  4. ^ Jump up to: a b c d e f g Copeland, Peter (February 2009) [September 2008]. Redlich, Gert (ed.). "Manual of Analoque Sound Restoration Techniques". London, UK: The British Library Sound Archive (www.bl.uk.). Chapter 9. Reciprocal noise reduction. Archived from the original on 2017-11-05. Retrieved 2017-11-05 – via Deutsches Hifi-Museum, Wiesbaden, Germany. (NB. Strongly biased from a British perspective, but nevertheless very knowledgeable.)
  5. ^ Bruch, Walter (September–October 1983). "Von der Tonwalze zur Bildplatte (Teil II) - Entwicklung der Magnetbandtechnik". Funkschau [de]. 100 Jahre Ton- und Bildspeicherung (in German). Vol. 55, no. 18, 19, 20, 21. Munich, Germany: Franzis-Verlag GmbH. ISSN 0016-2841. Archived from the original on 2017-12-08. Retrieved 2017-12-08.
  6. ^ Jump up to: a b c d e f g h i j k l m "Das CX Rauschunterdrückungs-Verfahren für Schallplatten". AUDIO [de] (in German). November 1982. […] Drei Jahre entwickelten die Elektronik-Ingenieure Louis A. Abbagnaro und Daniel W. Gravereaux (Columbia Broadcasting Corporation) am CX-Verfahren. CX bedeutet soviel wie Compatible Expansion […] und ist ein Rauschunterdrückungsverfahren für Schallplatten. Durch eine spezielle Komprimierung und anschließende Expansion der Musik bei der Wiedergabe von der Schallplatte soll dieses Verfahren die Dynamik einer Schallplatte um 20 Dezibel auf einen Wert von insgesamt 80 Dezibel erhöhen. Plattenrauschen, Knistern und Knacken sowie Rumpelgeräusche sollen mit diesem Verfahren unhörbar werden. […] Die wichtigste Bedingung bei der Entwicklung von CX war neben der Geräuschreduzierung und Dynamikerweiterung die Kompatibilität. […] Die CX-Platten sollen ohne gravierende Qualitätseinbußen auch ohne den CX-Decoder abspielbar sein. Doch […] CX-Lizenznehmer Teldec schreibt für das Abspielen von Klassik-CX-Platten unbedingt die Verwendung eines CX-Decoders vor. […] Grund […] Nur mit Hilfe eines CX-Decoders ist die Natürlichkeit der Musikwiedergabe gesichert. Das ist besonders bei klassischer Musik wichtig. Beim Anhören ohne Decoder werden […] vor allem die Höhen unwirklich überbetont und hart, außerdem wirkt auch die Dynamik, bedingt durch die fehlende Expansion, eingeengt. […] Bei Popmusik-Platten fällt indes dieser Effekt meist nicht so deutlich auf. Da viele dieser Platten keine sehr großen Dynamik-Unterschiede haben, stört die fehlende Expansion kaum. Was aber bleibt, ist die etwas überzogene Höhenwiedergabe vor allem beim Abhören über hochwertige HiFi-Anlagen. […] Das Angebot an Decodern ist zwar noch nicht sehr groß, doch sehr viele Firmen haben inzwischen CX-Lizenzen erworben. Einen hervorragenden Eindruck hinterließ der Kort-Decoder […] beim Hörtest. Nicht nur, daß er sich mit Hilfe eines Reglers und eines Zeigerinstrumentes problemlos auf die Signalstärke der Schallplatte abgleichen läßt, er überzeugte auch klanglich. Der Telefunken Decoder RN 100 CX und auch die in den beiden Plattenspielern RS 120 CX und RS 220 CX integrierten Decoder sind direkt mit einem Entzerrer-Vorverstärker gekoppelt. Moving-Coil-Systeme lassen sich damit also nicht betreiben. Klanglich gute Ergebnisse liefert auch der CMLab-Decoder aus den USA, wenn auch der Kort-Decoder klanglich leicht überlegen ist. Prototypen von CX-Decodern präsentierten unlängst auch die deutschen Firmen Backes & Müller sowie Thorens. Wann diese Geräte in Serie gehen, steht noch nicht fest, doch eines ist sicher: Viele Unternehmen werden in Zukunft CX-Decoder, ob separat oder in Verstärkern oder Plattenspielern fest eingebaut, anbieten. Und damit kann auch die konventionelle Platte, vorausgesetzt, sie ist CX-codiert, störungsarmen Musikgenuß bieten. […] Im Prinzip arbeitet das Rauschverminderungs-System CX ähnlich wie andere, bei Cassettenrecordern eingesetzte Rauschminderungs-Systeme, beispielsweise Dolby B/C oder High Com. Nur werden hier beim Überspielen der Musik vom Masterband auf die Schneidemaschine zur Herstellung der Masterfolie die Signale durch einen speziellen Kompressor geschickt. Dieser schränkt die Dynamik der Musiksignale ein, senkt also laute Töne um einen definierten Betrag ab und hebt umgekehrt leise Signale ebenfalls definiert an. […] Bei der Wiedergabe der fertigen CX-Platte geschieht genau das Gegenteil. Ein Expander, das Gegenstück zum Kompressor, erweitert die Dynamik wieder, hebt also die lauten Töne wieder um den ursprünglichen Absenkungsbetrag an und senkt die leisen Töne um den ursprünglichen Anhebungsbetrag wieder ab. […] Beim Absenken der leisen Töne kommen Störgeräusche, wie etwa Rauschen und leise Knacker, die von der Platte herrühren, nicht ungeschoren davon. Sie werden in gleichem Maße mit abgesenkt und dadurch fast unhörbar. Die Gesamtdynamik einer CX-Platte kann, so die Erfinder, bis zu 80 Dezibel betragen. […] Die Investitionen für einen CX-Decoder betragen etwa 300 bis 500 Mark. […]
  7. ^ Jump up to: a b CX-Encoder/Decoder Model 1181 (PDF). 6/82 (preliminary ed.). Sun Valley, California, USA: United Recording Electronics Industries (UREI). June 1982 [1981]. ark:/13960/t0ms7nx1d. Archived (PDF) from the original on 2021-05-02. Retrieved 2021-05-02. [2][3] (23 pages) (NB. Includes circuit diagram of the UREI CX Mastering Encoder/Decoder Model 1181 including half-speed modification.)
  8. ^ Jump up to: a b Kamfenkel, Klaus (November 1982). "Ein Tag mit Gerhart Metzler - Auf Schritt und Tritt verfolgte stereoplay einen der maßgeblichen HiFi-Macher bei der Arbeit". stereoplay (in German). Stuttgart, Germany: Vereinigte Motor-Verlage [de]. ISSN 0172-388X. Archived from the original on 2021-05-05. Retrieved 2021-05-05 – via Hifi-Museum.
  9. ^ Glaberson, John B. (1983-03-15) [1980-05-29]. "Signal compression and expansion system" (PDF). CBS Broadcasting Inc. U.S. patent 4,376,916. Archived (PDF) from the original on 2021-05-03. Retrieved 2021-05-04. [4]
  10. ^ "Slow Progress Seen in CBS' CX Campaign". Billboard. 1982-02-20. p. 3.
  11. ^ Jump up to: a b c d Roberts, John (2017-10-20). "Re: Vinyl CBS CX Encoding". GroupDIY. Archived from the original on 2021-05-03. Retrieved 2021-05-04. […] Back in the early 80's I got a phone call from the editor of Popular Electronics, and he offered me the Christmas issue cover of the magazine (then 500k circulation) if I designed a kit CX decoder. […] I was made a CX licensee by CBS and received the full CX documentation package along with a stack of CX albums. I only had a few months to crank out the design so I put the CX decoder into an existing tape NR package from another kit of mine. […] The CBS documentation included two proforma decoder designs, that apparently the other licensees copied verbatim. I didn't and discovered a mistake in the playback time constants (about 10% error), so I corrected that for my design, and notified my contact at CBS. […] The encoder was designed and fabricated by [UREI]. […] Literally weeks before my kit article hit the street, I was attending the AES show in NYC and decided to visit the UREI booth […] When I mentioned that I found the mistake in the CX documentation their eyes lit up and they said, so you're the guy. […] It turns out that there were already tens of thousands of decoders out in the wild with the wrong time constants in them, so CBS decided to change the time constant in the encoder to agree with the mistake. Of course […] CBS neglected to tell me, so I was about to publish the only correct CX decoder design, that they were making wrong by arbitrarily changing the system specifications, without telling me. […] I was able to make the value tweak to my design, and change my kit article before it printed, so we were back in sync... BUT all the records already encoded and pressed would never agree with all the decoders out in the market, and only new pressings after that change would be completely correct. […] I went to such lengths to deliver accurate decoding that I even specified a tantalum cap for the side chain time constant circuit because the UREI encoder used tantalum in their compressor design. […] in a side chain circuit when charged and discharged with different impedances the capacitor's dielectric absorption can influence the capacitor's waveshape. […]
  12. ^ "JRC NJM13600/13700 - Dual Operational Transconductance Amplifier" (PDF). New Japan Radio Co., Ltd. 2006-04-06. Archived from the original (PDF) on 2020-01-29. (6+1 page)
  13. ^ LM13700 - Dual Operational Transconductance Amplifier with Linearizing Diodes and Buffers. National Semiconductor. June 2004. DS007981. (26 pages)
  14. ^ "V13700D/M - Dual Operational Transconductance Amplifier with Linearizing Diodes and Buffers" (PDF). coolaudio. Archived (PDF) from the original on 2021-05-05. Retrieved 2021-05-05. (29+1 pages)
  15. ^ "LM13700 - Dual Operational Transconductance Amplifier with Linearizing Diodes and Buffers" (PDF). Texas Instruments. November 2015 [November 1999]. SNOSBW2F. Archived (PDF) from the original on 2021-05-05. Retrieved 2021-05-05. (37 pages)
  16. ^ Jump up to: a b c d Taylor, Matthew "Mat" (2017-10-19). "CX Discs: Better, Worse & the Same as a normal record". Techmoan. Archived from the original on 2021-12-21.
  17. ^ Jump up to: a b "CBS Stresses CX Commitment - Seeks more Hardware Firms' Support for System". Billboard: 4, 79. 1983-01-29.
  18. ^ Jump up to: a b "ICs for Consumer Applications - Audio Application - Other Application". Hitachi Quick Reference Guide to Integrated Circuits and Discrete Semiconductor Devices - Preferred European Type-Selection. Hitachi. 1984. pp. 5, 46. Retrieved 2017-11-09. […] Type No.: HA12043, Outline: DP-18, Functions: CX NR-System for MCA System, Remarks: NR Effects 14 dB […] Type No.: HA12044, Outline: DP-18, Functions: CX NR-System, Remarks: NR Effects 20 dB […]
  19. ^ Jump up to: a b "CX-dekoder - grammofoon weergave zonder ruis" [CX decoder - phonograph record playback without noise]. Elektuur - Maandblad voor Elektronika (in Dutch). Vol. 23, no. 3 #233. Beek, Netherlands: Elektuur B.V. March 1983. pp. 3-68–3-76. ISSN 0013-5895. ark:/13960/t56f16p1t. Retrieved 2017-11-09. (NB. This article describes a do-it-yourself CX decoder based on the Hitachi HD12044 chip.)
  20. ^ Dyson, John S.; Hess, Richard L. (2019-03-12). "DYSON-HESS Noise Reduction Decoder System" (PDF). 0.7.1a. Archived (PDF) from the original on 2021-05-08. Retrieved 2021-05-07. (23 pages)
  21. ^ Jump up to: a b "Adding CX". Video: New Products. Billboard. 1982-05-01. p. 42.
  22. ^ Laserdisc - CX Compression Specification for Laservision Videodiscs (PDF). Pioneer. 1982-08-12. ark:/13960/t0ms7nx1d. Archived (PDF) from the original on 2021-05-02. Retrieved 2021-05-02. (8 pages)
  23. ^ Jump up to: a b Badger, Greg; Allen, Richard (October 1982). "The Audio Side Of The Laser Videodisc". Affiliation: Pioneer Video, Inc., Costa Mesa, California, USA. AES Convention: 72. Paper Number: 1935. {{cite journal}}: Cite journal requires |journal= (help)CS1 maint: location (link)
  24. ^ Roberts, John (March 1983). "CX - an approach to disc noise reduction". Studio Sound: 52–53.
  25. ^ "(unknown)". Selektor. Elektor (in German). Vol. 1981, no. 12. Elektor Verlag GmbH. December 1981. ISSN 0932-5468. CODEN ELKRCM. {{cite magazine}}: Cite uses generic title (help)
  26. ^ "CX-Dekoder - Schallplattenwiedergabe ohne Rauschen". Elektor (in German). Vol. 1983, no. 3. Elektor Verlag GmbH. March 1983. pp. 3-34 – 3-??. ISSN 0932-5468. CODEN ELKRCM. Retrieved 2021-05-02. (NB. Includes circuit diagram.)
  27. ^ "CX and DNR - the latest in noise reduction". Elektor – up-to-date electronics for lab and leisure. Elektor Publishers Ltd. February 1982. pp. 2-41–2-45. ISSN 1757-0875. ark:/13960/t5bc9qf8v. Retrieved 2021-05-05.
  28. ^ "CX e DNR - Gli ultimi sviluppi nella riduzione del rumore" (PDF). elektor – elettronica - scienza tecnica e diletto (in Italian). Vol. 4, no. 37. Jacopo Castelfranchi Editore [it] (JCE). June 1982. pp. 6-49–6-53. Retrieved 2020-07-12. (NB. Includes circuit diagram.)
  29. ^ "CA3280, CA3280A - Dual, 9 MHz, Operational Transconductance Amplifier (OTA)" (PDF). Intersil Americas Inc. May 2002. FN1174.6. Archived (PDF) from the original on 2021-05-05. Retrieved 2021-05-05. (10 pages)
  30. ^ "(unknown)". Gerätevorstellung. Funkschau [de] (in German). No. 6. Munich, Germany: Franzis-Verlag GmbH. March 1983. pp. 94–. ISSN 0016-2841. {{cite magazine}}: Cite uses generic title (help)
  31. ^ Phase Linear CX-Dekoder Modell 220 (in German). 2017. Archived from the original on 2017-11-05. Retrieved 2017-11-05. (NB. New-old stock CX encoders originally manufactured in the 1980s in the US by Phase Linear, refurbished with new capacitors, an improved power supply and other tuning by Altmann Industrieelektronik GmbH (aie), Germany.)
  32. ^ Roberts, John (January 1982). "$70 decoder for new CX records - Provides 20 dB noise reduction when used with CX-encoded records" (PDF). Popular Electronics. Vol. 20, no. 1. Ziff-Davis Publishing Co. pp. 39–44. ISSN 0032-4485. Archived (PDF) from the original on 2021-03-08. Retrieved 2021-05-02. [5] (6 pages) (NB. Includes circuit diagram.)
  33. ^ "NE5517, NE5517A, AU5517 - Dual Operational Transconductance Amplifier" (PDF). Revision 4. ON Semiconductor / Semiconductor Components Industries, LLC. June 2013. Archived (PDF) from the original on 2021-05-05. Retrieved 2021-05-05. (16 pages)
  34. ^ Cohen, Joel (December 1981). "HI-FI CX Decoder For Records". Build This. Radio-Electronics. Vol. 12, no. 12. Gernsback Publications, Inc. pp. 43–46, 75. ISSN 0033-7862. ark:/13960/t56d7cw1h. Retrieved 2021-05-04. [6]
  35. ^ Einzelbaustein RN 100 CX (flyer) (in German). Telefunken. 1982. Archived from the original on 2021-05-02. Retrieved 2021-05-02.
  36. ^ Böhm, Peter, ed. (2012). "CX Decoder RN100CX". Radio Museum (in German). Archived from the original on 2021-05-05. Retrieved 2021-05-05.
  37. ^ "Engineering Data Allison EGC-101 and related circuits" (PDF). Nashville, Tennessee, USA: allison research, inc. Archived (PDF) from the original on 2021-05-05. Retrieved 2021-05-05. (13 pages)
  38. ^ Holtwiesche, Markus (2018-07-19) [2017]. "CX-Decoder/-Expander für CX-codierte Langspielplatten (Vinyl)" (in German). Archived from the original on 2021-05-01. Retrieved 2021-05-02.
  39. ^ Holtwiesche, Markus (2021-02-19) [2018-01-31]. "CX-encoded Vinyl Records: CX-Expander/-Decoder". diyAudio. Archived from the original on 2021-05-03. Retrieved 2021-05-03.

Further reading

[edit]
  • CBS CX Expander Calibration Record (Vinyl LP). CBS. 1981. CX-REF. Archived from the original on 2017-11-05. Retrieved 2017-11-05. 7-inch. 33-1/3 RPM. Band 1: Left Channel Calibration 1000 Hz, 3.54 cm/sec RMS. Band 2: Right Channel Calibration 1000 Hz, 3.54 cm/sec RMS.
  • CX Sampler: CBS Records Introduces CX - The quiet evolution in audio (Vinyl LP). CBS. 1982. P16859 CXSM 170258 [Popular] / 170259 [Classical]. Archived from the original on 2021-05-03. Retrieved 2021-05-04. 7-inch. 33-1/3 RPM. Contents: Side 1: 1. Loverboy - Workin' For The Weekend [3:40], 2. Maynard Ferguson - Don't Stop 'Til You Get Enough [3:11], 3. Billy Joel - Los Angelenos [3:47], 4. Angela Clemmons - Give Me Just A Little More Time [4:03], 5. Willie Nelson - Stardust [3:50], 6. Philharmonia [Orchestra] London - Wagner: The Flying Dutchman - Overture Conductor Lorin Maazel [5:33]. Side 2: 1. The London Symphony Orchestra - Star Wars (Main Theme) Conductor Ettore Stratta [3:55], 2. Toronto Symphony Orchestra - Rossini-Respighi: La Boutique Fantasque (Excerpt) Conductor Andrew Davis [8:46]. Quotes from the sleeve: A CX record is completely compatible with your current stereo system. You can play it and enjoy it now. However, with a CX decoder added to your system, you'll experience a startling difference in the dynamic range of your music. That's because when played with a CX decoder, a CX record will deliver clear, bright, noise-free sound-comparable to what you'd hear in an actual concert hall environment. [7]
  • "Informations- und Meßplatte CX-Störunterdrückungssystem". Telefunken. 66.10 230-01-1. Archived from the original on 2021-05-03. Retrieved 2021-05-03. (NB. 17 cm record.) Richter, Georg, ed. (2010-02-06). "Das 'CX' Störunterdrückungssystem der CBS" (in German). Archived from the original on 2021-05-03. Retrieved 2021-05-03.
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CX (noise reduction) - Wikipedia
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