re: CD player features Edition: 16 Jan 92 This is a summary of my experiences and opinions concerning CD specs and the utility of specific player features. This is the result of seven years of CD watching, buying and consulting. It is alphabetical by feature after the opening "kit" section. This guide does not discuss tips on the evaluation of audio equipment in general. CD audition kit While shopping for a player, I take along the following. You might want to neighbor with friends who have players and see if you can assemble a similar kit. 1. Out-of-band Test Disc: I use the Pierre Verany PV.788031/032 set. It has 106 tracks of "digital torture tests", like out-of- spec rotational speeds, track pitch, data patterns and drop-outs. An acceptable player should be able to handle every test except drop-outs over 2 cm. 2. In-band Test Disc: I use the "Denon Audio Technical CD", 38C37-7147. It has 99 tracks with all kinds of test signals. The CBS CD-1 is also useful, but is more expensive and difficult to find. 3. A "full" CD: This is a CD with at least 70:00 minutes on it. It has been reported that some players (especially portables) have trouble tracking near the outer edge of the CD (which is read from the inside out). I use: Lightfoot,Gordon: Gord's Gold; Reprise 2237-2 This CD is 75:53 minutes long. CDs over 72 minutes long are possible only by shading the lower limits of the Philips/Sony specs for linear velocity and track pitch. Make sure your proposed player can handle *all* of tracks 1 thru 18 on Pierre Verany disc #2. 4. Known bad CDs: Aside: if you will be in the market for another player in the future, think twice before you return your next defective CD. I have two of these. One has a pressing defect on the label side that goes down to the data layer. The other has an optical defect on the data side, plus other undetermined problems. Players DO exist that can play at least one of these discs (many can't), and comparisons of failure modes are interesting in any case. A badly scratched CD is useful if you can't locate a factory-defective disc. Audio equipment stores often sell off their abused demo discs at a considerable discount. Also, if you can find an off-center CD, this is a useful test article. Pierre Verany disc #2, tracks 19 thru 23 test the capability for a player to handle calibrated marginal pits. Any player should be able to handle these tracks. 5. A CD3 in an adaptor and a warped CD: Many players are not tolerant of CDs that are out of spec physically. If you can't find a warped or dished CD, using a 3-inch CD in a 5-inch adaptor is a useful substitute, as these adaptors tend to be thicker than normal CDs. 6. Programming test cases: A requirement while seeking my current player was that it be able to do "smooth joins" of sequential tracks in program mode. I use Mark Knopfler's "Local Hero" soundtrack, Warner Bros. 9 23877-2 (Vertigo 811 038-2) for this. Tracks 10 & 11 are really one song, with a soft transition. Andreas Vollenwieder CDs are also commonly mastered this way. See "Dead band" for more on this. 7. An indexed CD. A particularly nasty example is CBS (now Sony) MK37779, the Bach "Goldberg Variations" by Glenn Gould (the 1981 recording). This CD has *one* track with 31 indexed selections (the variations). See "Indexing", below. Analog stage Although many afficionados insist that this is the most important aspect of CD player design, be aware that there's a lot of gimmickry going on. Several vendors have the drive/digital circuits in a separate box from the analog circuits. Onkyo has a fibre optic link from the digital to the analog circuit. California Audio Labs and Carver have a vacuum tube analog stage. Linn has a separate sync cable. Use your ears. Take a test disc, scope and audio analyzer if you really care about this issue. Auto-pause A front panel switch. When enabled, the player automatically goes into PAUSE at the end of the current track. This is useful if you are taping specific selections and the player is not programmable. My first player (Sony CDP610ES) had this feature, and I used it from time to time. Auto-start A rear panel switch. When enabled, the player automatically begins play of the current disc at power up. Perhaps useful if your alarm clock has AC-out and you don't like rising to "Morning Edition". Beams, number of Regardless of the number of "beams", there is almost always only one LASER. The CD makers would have you believe that three beams are better than one. I have found it to be irrelevant. See later comments on Error Correction. CD3 It looks like "CD singles" may not be here to stay, but it is also possible that a CD3 exists that contains material not available on "real" full-size CDs. My criteria for CD3 support in a player are: - The player must at least accept a 3-to-5-inch CD3 adaptor. My second machine (NEC 607E) required some tray modifications before it would accept an adaptor. - Preferrably, the tray would have a separate loading indentation for CD3. Most do now. CDV (CD-Video) CDVs contain up to 20 minutes of ordinary CD audio, and will play on all existing players. They also contain up to 6 minutes of CLV full-motion video/audio, which portion will only play on a CDV-compatible CD player, or a CDV-compatible laser video disc (LD) player. Most current LD players accept CDV (and CD). Very few (3,5-inch media only) CD players accept CDVs and have video out. Frankly, I'm not convinced that 5-inch CDV is here to stay. To my knowledge no new titles have been released since 1989. I don't consider it to be a priority for a CD player. It is a minor consideration in an LD player. Note that the logo (((CD-Video))) is also used on some 8- and 12-inch LDs having digital soundtracks. If LD and/or CDV interests you, consider the Pioneer CLD-M90. It is a basic LD player and 5-disc CD carousel changer. It plays everything from CD3 thru 12" LD, and has a CD tray design that meets my criteria. If a combi player interests you, I have separate articles available on laser video. CD+G CD+Graphics was supposed to hit the market in 1989. It uses the subcode channels on the CD to produce still- frame graphics. Presumably, this can deliver useful stuff, like lyrics, liner notes and related art. So far, only JVC sells a CD+G-compatible player in the U.S. You will need a cable to your TV to use it. CD+G is *not* the same as CDV, and current CDV (LD combi) players cannot display CD+G images. CD-I players can display CD+G graphics. They're pretty expensive yet, havinf a dedicated on-board MC68000 CPU chip, plus video circuitry and operator interface widgets. DAC, one vs two Sharing of a single DAC (Digital to Analog Converter) means that the DAC must be higher speed (two channels at 88 KHz vs one-each at 44 KHz), and means that one channel will always be about 11 uSec behind the other, (unless an analog sample-and-hold is used). This amounts to about 0.15 inch at the speakers. Theoretically, a sensitive ear might detect this phase shift (group delay) on earphones. It has yet to be reported. Get a test disc and use your ears. This delay can affect surround sound decoding. If you are buying an LD combi player, and your surround decoder does not have "auto azimuth", insist on dual DACs. DAC, 14- vs 16-bit The data on the disc is 16-bit, and theoretically, 16-bits should provide greater resolution than 14. However, a 16-bit DAC costs more than a 14. A pair of them even more so. The current Philips (Magnavox) chip set is 16-bit, and Meridian (a maker of audiophile Philips-based players) has declined to use it in their latest machine. Here again, the results, as perceived by you, are more important than the technology employed. For the curious, the Pierre Verany test discs contain a sample of music encoded at 16-, 15-, 14- and 8-bits. DAC, 18-, 20-bit? Yamaha and Denon upped the "bit-ante" with their 18- and 20- bit machines. The raw data on a CD is, of course, only 16- bit, but it is of interest to know the bit-width of the error-correction, digital filter and DAC stages. For purposes of numbers games, however, a more important issue is linearity (see that section). A linear 14 bitter probably sounds as accurate as a sloppy 20-bitter. Dead band There are two sides to this issue: 1. Many CDs are produced such that the music doesn't really stop altogether between tracks. If you program a selection of sequential tracks on such a disc, you probably don't want to hear a pause/hiccup between tracks, just a smooth join. Most players don't behave properly in this respect. (It is not yet possible to get a smooth join on non-sequential tracks. Even the fastest players have about 0.5 sec track-to-track seek. It could also be done using copious amounts of read-ahead RAM, but no one is doing that yet.) 2. On the other hand, you might want some extra dead band between tracks. If you are taping, some cassette players require a minimum of 3 (or 5) seconds to permit scanning/skipping. Some players introduce 3 seconds always. Some other machines have a switchable deadband. But make sure the "no deadband" position really is "smooth join". Display modes You don't normally get all of the following, nor all at once, but may need to select a set via a switch. Here's my observations on each. See also "Header read-out" Track, Current Mandatory Track, Remaining time in Useful when taping Track, Elapsed time in Useful if previous n.a. Tracks, Remaining Don't care CD total, Elapsed time Don't care CD total, Remaining time Useful Index, Current Mandatory if indexing Selections Programmed Confirms program Total/remaining prog. time Useful Drop-out tolerance CD players are supposed to be able to fully correct up to 0.2mm of completely missing data (drop outs) on a track. Theoretically, they can reconstruct up to 2.47mm drop outs. Theoretically, they can interpolate (fake) missing data of up to 8.5mm in length. Anything they can't reconstruct or interpolate, they are supposed to simply mute. The Pierre Verany discs contain test drop outs of between 0.5mm (38 uSec.) and 4.0mm (3.08 mSec.). The average player can handle at least 1.0mm. See "Error Correction", below. Dub programming If you plan to make cassette copies of many your CDs, be aware that some CD players have a mode which allows the player to pick CD tracks that will fit on one side of standard cassettes, play them, then auto-pause. Error correction There are VAST differences in error correction performance among the players out there today. Using my "known bad" CDs, some players eject the discs, some can't "find" them, some skip, some get stuck on track, some tick, and a few can actually correct the errors. The Pierre-Verany dropout bands are useful in measuring player error correction. The player's performance on such discs may tell you how well it will handle dust/dirt and scratched CDs. Also, you may well want to avoid a player that has LOUD ticking artifacts on bad CDs. These ticks might damage your tweeters. Filters, A vs D There is a visible ('scope) difference between digital and analog filtering of 1 KHz CD square waves. It appears that you can choose between post-transient ringing (analog) or a smaller amount of ringing present both pre- and post-transient. Take a favorite CD and use your ears instead. Golden-eared stuff The single-crystal, oxygen-free, tiptoe, stabilizing brick litz-wire fraternity is *this* close to admitting that, maybe, just maybe, if someone forced them to accept a CD player at gunpoint, they might allow it into their home. Vendors are now catering to this market. I already mentioned some of the theatrics under "Analog stage". You can also buy green marking pens for the disc edges, Armour-All coating and a rubber "CD stabilizer" to slap on the CD before play. Exotica, tomfoolery and quackery is invading the digital domain, just as it has in analog land. There are conflicting reports concerning error/mute rates using a stabilizer. I am skeptical though, when they're asking $25.00 for what amounts to a rubber CD with no signal on it. I am also leery of "laser cleaning" CDs and CD media cleaners in general. There are reports that *all* CD cleaners will *increase* the error rate of a mint-condition CD. Header read-out Many players automatically spin-up a freshly inserted disc and display the total time and number of tracks. This info is often not found on the CD packaging, and the display may be more accurate than the packaging. Although this is useful, make sure that the player is runnable/programmable during this operation, otherwise it may just amount to a frustrating delay. Indexing The major cueing point on a CD is the TRACK (up to 99 per CD). A few (mostly classical) CDs also have a subcuing within tracks, called INDEXes (up to 99 per track). If you are a student or technical analyst of classical music, consider getting at least index display, if not seek-to-index capability. Very few players are index programmable. The Pierre Verany test discs contain one indexed track. The CBS CD-1 linearity tracks are also indexed. LaserDiscs There are several machines on the market that can also play 8- and 12-inch laser video discs (LDs) in addition to CDs (and possibly CDVs). LD is a whole different topic and beyond the scope of this article. I have others on that topic. Linearity When the digital information on the CD specifies audio dB levels of, say, -90, -75, -53, -29, etc., does the analog output stage produces those levels, or instead -81, -64, -57, -28? DACs are not all created equal, and cheaper ones may be significantly non-linear, particularly at low levels. This is difficult to casually test in store, unless you have sensitive ears and some known-linear CD material. One test I might suggest is listening to tracks 32 and 33 of the aforementioned Denon test CD. These tracks contain a 1001 Hz tone at -60 dB. If you hear anything other than a pure sine wave and hiss (especially any raspiness or buzzing) suspect non-linearity. The level of hiss may also vary from player to player, and will tell you about signal-to-noise ratio. The CBS CD-1 also several tracks useful for informal linearity testing. Track 6 is -60 dB. Tracks 18 and 19 index down to -100 dB with and without dither. Track 20 does a fade-to-noise with dither from -60 dB. Memory, non-volatile If you use programming regularly, you will tire of punching in the same tracks over and over again. An increasing number of machines offer what Philips/ Magnavox terms "Favorite Track Selection" that can store the programs for some number of discs (identified by their headers). Philips FTS handles 226 discs (785 total tracks). Make sure the NOV-RAM (non-volatile memory) is deep enough for your library. Also consider whether or not you'll want to edit the NOV-RAM. On current FTS machines, each edit consumes a "disc number". When you reach the maximum (226 or 255), you have to erase the entire NOV-RAM to add entries. Sony also makes FTS machines (although they call it "Custom File"). If the machine also has "shuffle" mode, inquire if both features may be used simultaneously. My current Sony CDP-85ES can't, but the "custom file" is still very useful. Multiple discs Several vendors offer magazine-loading machines Pro machines can handle discs in the hundreds. Consumer machines are up over 20, some with multiple magazines. Carousel models rarely handle anything other than 5 discs. Your biggest decision is: carousel or magazine? Things to watch for: * How easy is it to play just one CD? Reports on the 10-CD Sony say "difficult". * How deep is the program memory and can you skip from CD to CD? 20 steps out of a potential maximum of 990 tracks (10 CDs) is pretty silly. * How expensive are empty magazines? If they aren't VERY easy to load, they'd better be cheap enough to hold your whole collection. * If the player has "shuffle" or "random" play mode, is it truly random (preferred) or does it favor the currently mounted disc. Also, does it remember all played tracks from all discs? Reports are that many don't. Tracks get repeated. Suggestion on auto-changers: Unless you plan to load your whole collection into magazines: * Get a magazine-loader that also has a single-play tray or accepts a single-play "magazine", or; * Get a carousel-style changer. Noise No current CD player should have any AUDIO signal noise. Drop a CD in, wait for deadband and crank 'er up. You should hear nothing. There is also an intentional data=0 track on the CBS, Pierre Verany and Denon Audio Technical Test CDs. There should also be no change when switching from play to pause on zero-signal or deadband tracks, nor any clicks or pops from the switch. Do check for MECHANICAL noise. Loading drawers can be pretty noisy, but once it spins up, you should hear nothing. Be suspicious of ticking - it could be seeking on an off-center CD, but then again... Output, headphone If you have an old or noisy amp/receiver (as I did until recently), listening to phones directly from the CD player is lots quieter. If you have a clean amp, CD phone-out may be irrelevant. But, if you think you might use the CD phone-out: 1. Make sure it has a level control. Many players have a fixed output level - useless in my opinion. 2. Make sure it can drive your favorite "cans" - bring 'em along. The headphone amp in many players does not provide a signal of the same quality as the line output. So test carefully if you will be doing much phone listening. Output, line adjust If you are likely to switch often between your CD player and other signal sources (LP, FM, tape), it might be nice to be able to adjust the line-out of the player to match the volume levels of the other sources. Output, subcode/dig. Many players have this "future use" output on the back. Frankly, I think the subcode out is less likely to ever be used than the "TV Adaptor" port of 1940's FM radios (which wasn't, you'll recall). An increasing number of players have true digital audio output ports, for use with stand-alone PCM (D/A) boxes. If you are considering one of these setups, you probably aren't reading this. In any case, not all consumer digital recorders use 44.1 KHz digital in. There are several standards for digital connectors, so make sure all your equipment will be compatible. Oversampling Anti-aliasing requires steep filtering of frequencies above 22 KHz both pre-ADC and post-DAC, due to the 44.1 KHz sampling frequency. Digital Signal Processing theory permits a gentler filter post-DAC if the apparent sampling frequency is increased by more frequent re-sampling, interpolation or simply inserting zeroes. There exists at least one machine claiming 16x oversampling and NO filtering. This also means the DAC has to run faster, so there are tradeoffs. As with digital vs analog filtering - take some favorite CDs and use your ears - mine can't tell. If the player does not employ oversampling, be sure to listen to the frequency sweep track on your test CD. It may reveal problems with intermodulation of the intended (baseband) signal and ultrasonic artifacts. The sweep should be smooth pure tone, with no noise, accompanying tones or discontinuities. Portables Test portables to the same standard as desktop players, plus, consider the following attributes unique to the breed: - Does it include both AC adaptor and batteries? Generally, lead-acid batteries are smaller (although perhaps heavier) than nicads, and lead-acids run longer. - How long does a fresh charge power the player. Look for a minimum of four hours. - Does the player also accept ordinary batteries? Does it accept retail nicads, or only custom nicads? - Does the player have a reasonably standard power connector and voltages? The Technics players, for example, do not. They use +/-9 vDC and a custom connector. They are virtually impossible for you to adapt them to auto use or user-supplied external DC. - How sensitive is the player to bumps and jolts? When it skips, does it pick up where it left off, or keep going from wherever it landed? - Does it have "line" out in addition to phone out? If so, you could consider using it as your home player, as well as your portable. - Does the player include phones? If yes, too bad. They are probably junk. Plan on separately buying a decent pair. Programming, A->B The most primitive kind of programming. It allows you to repeat from to . I've never used it. I'm told that musicians find it useful when trying to learn a piece of music. Programming, seq. With the player stopped, you specify up to [n] tracks to be played. No matter what order you enter them, they are played back sequentially. Make sure you know what [n] is for the player you are considering. I suggest it ought to be at least 16. Programming, random Most current generation machines are like this. They play back the selections in the order entered. I prefer this mode. See also "dub programming". Remote control Both my home machines have (had) remote. I use it. PAUSE - for when the phone rings Skip - To skip unliked stuff on non-prog player. I use this frequently when auditioning CDs of music I generally dislike. Search - What did I just hear? Where is that? Display mode - How much time left on this disc ? Volume - Was on player, now on receiver. I find this very useful. I suggest a remote volume that is handled by a servo motor on the potentiometer, rather than via a varistor of other active component that may eventually degrade the sound. Note - many players omit controls on the front panel that are on the remote. Make sure all the controls you care about are in all the places you care about. RUN/PAUSE All players should have this. Note that in PAUSE, the player stays on-track (perhaps at same pointer in buffer). The laser is ON and the motor is running. Don't leave your player like this all weekend - it's the same as playing, and consumes laser/motor life. Some players have a common RUN/PAUSE/STOP button, where STOP is performed by holding the button down for a few seconds during RUN. With such an arrangement, you can't go from PAUSE to STOP without going back to RUN for those seconds. My NEC is like this; a minor annoyance. Search, audible If you are searching for a specific passage (not on a track or index boundary), "search" allows you to "fast foward" (or back). "Audible search" allows you to hear snippets of the sound (every nth data track) as they fly by. It is very useful, in fact, I insist on two-speed audible search. Most machines have it today, although many require that you hold the single button down for several seconds before it shifts to the higher search speed. Seek, to-track A must, and no current machines are without it, that I know of. This allows skipping to the next or previous track. Seek, to-index Less common. See my comments on "Indexing". Shuffle mode Plays entire (unprogrammed) disc or your list of programmed selections in pseudo-random order. Might break up the potential monotony of some pop CDs. I find this mode very useful on CD auto-changers, when it is truly random. Shock resistance [The mechanical kind]. On average, CD players are much more resistant to skipping and mistracking due to vibration than LP turntables. Nonetheless, it's worth testing. I usually rap with knuckles. I also pick the whole player up and rock gently, simulating a weak floor rocking the equipment rack as someone walks (or dances) by. If you are considering a portable, be aware that none are presently suitable for jogging, and many not even for walking or playing on a car seat. Specifications All players have specs rarely encountered on AM, FM, LP tables and most consumer tape decks. Audibly, I have trouble telling most CD players apart. I suggest you let your ears be the judge. If they are sensitive, you are likely to hear differences greater than the published numbers would suggest. Tray styles Worry about this: What part of the CD is touched when you place it in the tray? The only answer I accept is: The outer or inner edge beyond the data area. I declined to purchase a player (Sony CDP-55) because the tray props the CD on three plastic legs right smack in the middle of the data area. Now they are padded, to be sure, but eventually, the CD is going to get scuff marks there, dispersing the laser light and increasing errors. Avoid players with in- data supports. A co-worker had four CDs destroyed by a CDP-35; it dropped the still-spinning disc onto the posts. (To Sony's credit, I should mention that they granted a complete refund on the player, and replaced the damaged discs.) If you insist on an in-data support design, insist on knowing how the player performs spin-down/braking. If it just drops the spinning disc on the pads, you might as well stay with LPs; they'll last longer. The ideal tray has three or four small pads at the outer edge that slope towards the center. A single center ring only slighter larger in diameter than the CD hole is also cool. If the player has flat outer pads, you can usually modify it by replacing them with sculptured gum rubber from a stationery store (as I have done with my NEC player). Warranty 1. Make sure that you are getting a U.S.-honoured warranty. Check the contents of the box at the store, especially if the price was too good to be true. If the unit is grey market, but the price is too good to refuse, make sure the player is specified to operate at 60 Hz, 110 or 120 Vac. There are reports of 100V Technics SL-XP7s overheating and operating erratically after extended use at 120 Vac. And, a replacement 120V adaptor will cost you $50. Also be aware that a a grey-market unit may not have an FCC ID, and may interfere like crazy with local TVs. 2. I suggest a minimum of 1/1 year parts/labor, and find out where the service center is. It has been reported that early Denon 1500s must be returned to Japan for service! Keep your sales slip and receipt, they are more important than the bingo card if something breaks. 3. I suggest avoiding store-provided extended warranties. Certainly reject them outright if they are over 4%-of-purchase-price-per-year (and remember that the store essentially gets a free ride during the mfr's warranty period). You can usually shut off the service contract sales pitch by asking: "What is the annualized failure rate and mean time between failure on this model and its predecessors?" Where to buy? Should you purchase in an audio specialty store, discount department store or by mail order? Generally, I prefer to purchase products locally, and at establishments that provide an adequate demo environment. If I cannot negotiate an acceptable price, I wait for a sale. I am willing to pay a few dollars more for: * Recourse: the factory sealed NEC player handed to me at the local dealer a year ago was defective. Replacing it would have been a non-trivial nuisance had I ordered it by mail. As it was, I took it back the next day and swapped it for a different (properly functioning) unit. * Hands-on access: many of the player characteristics listed in this guide do not appear in data sheets or magazine reviews. Further, telephone sales people usually know even less about a given player. Only live testing will tell. If you don't patronize your local dealers, they may not be there when it comes time to investigate replacement speakers or a new- -fangled DAT recorder. Finally, when you get your player home... Unless you bought the demo unit, re-run all the tests you performed in the store. Unit-to-unit variations are often greater than average model-to-model or brand-to-brand differences. Copyright 1989, 1990, 1992 Robert J. Niland All Rights Reserved Permission is granted for automatic redistribution of this article, via electronic, magnetic and optical media, in an unedited form, through any Usenet newsgroup where the article is posted by the author, through the Internet VIDEOTECH Digest and the Bitnet VIDTEK-L Listserv mailing list. Permission is granted for each Usenet reader, each VIDEOTECH or VIDTEK-L subscriber and each person who received this article from an ftp site authorized by the author or via electronic mail from the author, to retain one electronic copy and to make hardcopy reproductions of this edition of this article for personal non-commercial use, provided that no material changes are made to the article or this copyright statement. All other copying, storage, reproduction or redistribution of this article, in any form, is prohibited without the express written consent of the author, Robert J. Niland. Regards, PO Box 248 Bob Niland Enterprise rjn AT access DASH one DOT com Kansas http://www.access-one.com/rjn/ 67441-0248 USA Unless otherwise specifically stated expressing personal opinions and NOT speaking for any employer, client or Internet Service Provider.