Is a slow burn more reliable to play
Has anybody burned at different speeds to see if there is a difference in reliable replay? And are there any other important variables?
thanks, Obe 
Yes,
Burning at 1x is probably the most reliable burn speed but now, with the newer burners and better software, much higher speeds are possible. My new burner running Nero 6.0 will burn reliably at 12x. I did some tests with “Test & Burn” option selected and it didn’t start reporting errors and glitches until I got to 12x. All that said, 4x is probably the safest bet.
Don
Actually, Don, I don’t know if that’s true. I heard an interview on the net about this very topic (http://beradio.com/mag/radio_maximum_burn/) and this guy said you’ll get the best results from burning at the 1/3 - 2/3 maximum speed of your burner (I think - listen to the interivew) using media that is optimized for this range. He also suggests you do some testing at various speeds and see what you get from your own burner, of course.
I’m a slow burner myself. More time for the medium to be heated up and melt will create more of a groove… that’s all there is to it. There are plenty of variables, but I don’t think you can go wrong with a slow burn. i suppose the medium can over heat and turn to mush… but burn a CD and then rip it. Then, compare the channels to the original wav and reverse the phase. If it completely mutes in mono you knwo you have an accurate burn.
tempus,
Your advice may be correct…I was speaking from a listener’s standpoint. My ears couldn’t tell the difference after a 12x burn with Nero 6.0 and they hype 12x for audio work in their user’s guide. In fact, the proggie defaults to 12x for audio. One must manually select slower burn speeds. Supposedly, Nero pre-tests the media to determine the max/safest burn speed, then it burns at the max speed. I guess that I trust them to know what speed to burn at.
I did not try the tests that Bubba suggests but my ears were satisfied.
Another important variable is the quality of the blank disks. There are some off-brands that won’t make a good audio CD even at 1x. 
Don
PS: After all is said and done, I normally burn at 1x or 2x when doing any critical CDs.
The only real issue here is jitter, and playback on audio CD players that use the signal on the CD to clock the DAC output. Slower burns are more reliable. While 1x is probably overkill, the highest speeds should be avoided.
A very regular clock signal is necessary for digital audio to sound good. Jitter is any irregularity in the clock period, i.e., one sample interval being a little longer or shorter than the previous. Random jitter causes noise and distortion (more of the former than the latter). [Someone here convinced me it would only cause noise, but I subsequently read a research report that measured an increase in noise and THD as a result of jitter.]
When your CD drive writes the CD, it uses a clock signal generated in the CD burner hardware. A good jitter-free clock is not the easiest and cheapest thing to design and manufacture, and is one of the significant differences between a quality drive and a crappy one.
Ideally, jitter is zero. For any clock circuit, it actually has a normal distribution around zero, and the “width” of this distribution is a fixed amount in time (e.g., some number of microseconds or nanoseconds).
The clock speed is proportional to the CD spin rate. When they’re slow, the relatively fixed “typical jitter” is a very small percentage of the interval between clock pulses. The faster the CD goes, the bigger percentage of the interval it becomes.
For audio purposes, it’s the pecent jitter (percent of the interval between pulses) that matters. So, the faster the CD, the worse the audio.
For digital recording, jitter doesn’t matter until it gets sooo bad that the read circuitry is totally confused and loses a bit. This is what you’re testing when you test a CD in the burner, so it’s not a useful guide for audio CDs. This is also true for digital playback of audio CDs on your computer. (Most CD drives in computers can be configured to run in analog or digital mode, and most of us leave it in digital mode so we can rip CDs accurately.)
Unfortunately, there isn’t an easy way to measure your CD burner’s jitter. It’s not hard if you’re a tech-nerd and are good with oscilloscope and reading circuit diagrams. You’d scope the clock output from a CD player (the clock derived from the CD being played) and look for fuzzy lines rather than nice sharp lines. But without special equipment and opening up a CD player, I don’t know of any way to measure it.
So the only practical way to measure it is by listening, and make sure you’re using a player that uses the “recovered clock” rather than buffering the audio digitally and clocking it out using an internal clock.
My SWAG is that even a low-cost CD player should do fine burning CDs at 1/4 of their highest rate. If you burn a CD at the highest rate and it sounds good to you when played on your audiophile buddy’s best system (but using a portable CD player), then you’re probably fine with 1/4 that much jitter.
It might be interesting to do a double-blind study with your friend the audiophile/purist and a few other buddies. Burn two copies of a really good mix on CD (frankly, I’d use a commercial cut that I know is really well engineered, and something everyone likes) at highest speed and 1x, and label them A and B. Have someone repeatedly randomly select between the two (without telling the listeners), write down the label, and collect each person’s vote as to whether the CD is the “good” or “bad” one. Do a number of auditions, at least 10. When done, total up the votes independently for each listener, and learn who can tell the difference, if anyone.
BTW, there’s another cause of jitter other than clock problems: variations in the speed at which the laser switches on and off. It causes the same problem and is also exacerbated with speed, so it doesn’t need to be considered differently than clock-source jitter (unless you’re designing a CD burner, of course).
I arbitrarily choose to burn at around half of the nominal max burn speed of my drive. So since my burner is rated at “24x”, I usually burn at 12x. No problems so far.
I’m not convinced that a slow burn (1x, 2x, 4x) is necessarily better, unless the CD blank has been optimised for a slow burn . Most new CD blanks are allegedly optimised for higher speeds. I remember reading something about this, can’t remember where.
I’ve had very good luck with really cheap CD blanks, but I don’t use’em for anything critical. I recommend people buy mid-range ones, and make sure they have a decent writable coating on the non-burn side (which is the most fragile side). Write with a soft marker, don’t use CD labels - the adhesive can eventually attack the CD coating. And test as everybody’s mentioned before you make’em your standard.
While I can agree the recorder’s jitter is a factor, the jitter of a CD being played is a function of the CD player, since the CD is read into a buffer and the audio is “played” out of the buffer, clocked by the player’s own clock. The difference between a good cd and a bad cd (and a good and a bad cd player) is the amount of read errors. Less is better. Jitter in the recorder takes its place along with recording laser strength, focus and tracking accuracy, CD blank quality and other factors in determining whether you record a better or worse CD.
Finally, I know we all talk of “mastering” at home, but I think it’s a stretch to believe we are going to make error-free pressing-quality CD-A masters on our $75 beige burners. For any project where a glass master is going to be made and 500+ CDs made, I recommend saving all your finished tracks as 44.1 kHz 16 bit WAV files on CD-ROM (as data, not as a CD-A) or on a hard drive, and letting the CD duplicator have the responsibility of preparing the CD-A master. The reason for this is because if you give them WAV files, you’re certain you’ve handed off 100% error-free files, whereas if you hand them a CD-A, it’s more likely there will be errors.
I have indeed experimented with burn rates and found the following:
I have a Plextor 48x burner and use version 6 of Roxio. I’ve been using TDK and Maxell blanks (52x). I can hear a difference in burn speeds when I play the disc on my high-end stereo. On anything over 24x I clearly hear a degradation. At 48x I get audible ticks. The Plextor has a feature that can use a variable laser level at 4x speed (the slowest it goes is 4x). I always use this feature and the 4x speed when burning CDs for my clients and for duplication. I have an older expensive audiophile CD player that is very finicky about playing burned CDs and using the 4x speed is the only way I can get a burned CD to play reliably in this player, so there is something to that feature. I also can hear a subtle improvement in the sound quality at 4x compared to faster speeds.
BTW, thanks for the mastering tip, archimedes. The project I’m working on now will be printed with using a glass master. I’ll be sure to check with the duplicator for the best way to get them the files.
While I can agree the recorder's jitter is a factor, the jitter of a CD being played is a function of the CD player, since the CD is read into a buffer and the audio is "played" out of the buffer, clocked by the player's own clock.
This depends on the CD player. Most portables use the signal on the spinning CD as the timing source, or so I read in a rather authorative and extremely well-documented web page on the subject of jitter and CD burning. Sorry but I can't link to the source.
I agree about sending WAV files to the manufacturer! Eliminates a lot of potential problems. Just make sure to tell them whether to add inter-track time or not, deoending on whether you created the tunes to dovetail or not. Make sure you know how much time they'd add, so you can make sure that the gaps stay between 2 and 4 seconds. I think there's a standard amount (2 seconds?) but I'm not sure.
This depends on the CD player. Most portables use the signal on the spinning CD as the timing source, or so I read in a rather authorative and extremely well-documented web page on the subject of jitter and CD burning. Sorry but I can't link to the source.
I agree about sending WAV files to the manufacturer! Eliminates a lot of potential problems. Just make sure to tell them whether to add inter-track time or not, deoending on whether you created the tunes to dovetail or not. Make sure you know how much time they'd add, so you can make sure that the gaps stay between 2 and 4 seconds. I think there's a standard amount (2 seconds?) but I'm not sure.
Hi Jeff,
| Quote (learjeff @ Oct. 24 2004,17:52) |
|
This depends on the CD player. Most portables use the signal on the spinning CD as the timing source, or so I read in a rather authorative and extremely well-documented web page on the subject of jitter and CD burning. Sorry but I can’t link to the source. |
Think about that for a minute. You’re suggesting that the timing reference for the playback of 16 bit 44.1 kHz audio is going to be derived from a polycarbonate disc being spun by a $2 motor? In a portable device that’s being banged around?
If that hasn’t got you wondering, then how does the motor know how fast to spin the CD? (the spin varies from approx 8 rpm to 3.5 rpm inside to outside, to maintain constant linear velocity of the data at the laser). The answer is… a crystal oscillator, which provides the timebase to compare with the data rate coming off the disc. Furthermore, the raw CD datastream is interleaved, which means at least some buffering is required to marshall the decoded data and do error correction. Final factoid - if the raw data from the CD was being used for clock, the clock rate would exhibit wow and flutter, which is an attribute of ANY rotating mechanical playback system. And yet no CD player has wow and flutter specs… because the output is clocked out of the buffer by the oscillator.
Note that most CD portables nowadays advertise that they’re skip-free, can be used for jogging, etc. Buffer.
So I’m pretty sure that all CD players have a crystal oscillator (or equivalent) timebase for regulating the output sample rate, and that the data is played back from a buffer.
I can’t point to a web resource for this, but I’m sure they exist. I can recommend Principles of Digital Audio by Ken Pohlmann, which has a great chapter on CD audio.
OK, you convinced me! But aren’t you the one who convinced me that jitter (during recording) only adds noise, and not distortion? 
I don’t worry about all the speed stuff now I’m using a Plextor drive on my new DAW. It just “figures it out” for me .
I did have some problems with some Klone CD-Rs that I suspect where of poor quality but now I’m using better CD-Rs, Roxio just plows along & the CD-Rs seem to work just fine.
| Quote (learjeff @ Oct. 25 2004,16:19) |
| OK, you convinced me! |
Spoken like a gentleman.
(and thanks for not busting me on the CD spin rate. it's 8 to 3.5 rev per SECOND, not RPM. Duh.)
| Quote (learjeff @ Oct. 25 2004,16:19) |
| ... But aren't you the one who convinced me that jitter (during recording) only adds noise, and not distortion? ;) |
If I said that... then I'm in error. As you already know, jitter error adds distortion as well as noise. If I recall correctly, i think my point was that in the discussed situation (inexpensive sound cards), distortion due to clock jitter was likely to be well under the noise floor.
If you don't already have the Pohlmann book, get it. Given your technical bent, I'm certain you'd get alot out of it.
OK, I’ll put it in my amazon.com in-basket … along with 50 other books. 
So many books, so little time!