[aos]

>>>Rather than so-called "jittery" CD-Rs sounding consistently brighter than the source, they would sound brighter for a few seconds, darker for a few seconds, brighter, etc. Note that this is assuming the effect was brightening/darkening after all -- it might just as easily be fluctuations between normal dynamic range and reduced dynamic range, or fluctuations between a noise floor of -100 dB and -90 dB, for example. There are many other more plausible (IMO) effects than a simple brightening or darkening of the music. Try "muddying" vs. "clarifying," if you get my sense.

You could be right, and the effect on noise floor is what I have in mind as well, since many articles I've read describe change in S/N ratio thanks to jitter. And the noise floor would be frequency dependant as well. However, all of this is beside the point to me. I just wanted to point out that the effect is real, can be mathematically described, can be measured and analyzed and simulated. Since there is so much snake oil in audio, as an engineer I try to understand the theory behind a phenomenon, to see if it is possible that a particular thing (crystal, cables, whatever) can influence the sound. Once I understand that something is possible, I can be satisfied with relying on critical listening to determine its effect, whether it is audible and how does it change the sound. I reclocked my CD player recently and did notice a change but I'd be hard pressed to describe it, other that everything is more natural now. I have a few DACs here, and I'm about to make a DAC that does full reclocking so I'll be able to do more experimenting.

But, what the actual change in waveform is should really be left to scientific analysis. I don't feel confident in claiming that certain effect on sound (like brightness) is impossible without a solid proof, and the complexity of the formula prevents me from making a broad assumption here.

As for screen analogy, while it may not be perfect, someone seems to have distorted it wildly. I *NEVER* used brightness of pixels to describe jitter, but the distance between them. I clearly stated that the pixels have fixed, discrete values of brightness from 0 to 255 (8 bit) and that this would be analogous to reference voltage every DAC chip uses while recreating the waveform. It's the change in the inter-distance of the pixels that I refered to as jitter.

 

[robert_cyrus]

always burn as fast as you can, and use decent media.

http://www.emedialive.com/EM2000/starrett5.html

Quote:

Another claim heard from the audio community during its early dalliance with CD-Recordable technology is that audio recorders are the only way to go, whether because their 1X and 2X speed limitations keep things from getting too crazy or because some quality in their construction makes them more sympathetic to the audio task. To test this theory, discs from each brand in the test group were recorded at old, reliable 1X on an HHB Professional Recorder (which does not have the SCMS-only restriction of its "consumer" audio recorder counterparts). The discs were then tested for BLER, Burst, and six levels of E errors as seen in Table 11. Finally, we see that recording at 1X from a CD source to CD-R on a professional audio recorder has no significant effect on the quality of the disc, whether measured purely through error rates or by the human ear. So, the bottom line is that, when the world slowed down and we received our snailmail letter, delivered at 1X, it contained only good news and no bad news. But more importantly, by the time we got it, the news wasn't news at all--the 8X and 12X speedsters had beaten the pony express by a country mile and the message was the same: if you want to make your audio discs with the screamingest, fastest, baddest recorder on the block, go ahead. Let the timid confine themselves to recording at a snail's pace with the hope of improved audio quality. You know better.

i had another link that proved error rates reduced with increased speed, but i can't locate it at the mo'.

 

[Joe Bloggs]

Hey, here's a thought!

You know how the bitstream in CDDA represents the position where the speaker element is supposed to be at discrete time steps. (I'm sure someone can describe this much better but I hope you understand)

Now if a bit is messed up every now and then, the representation of the position at that point in the time domain is going to be messed up. If, as is likely, the position in the previous and next timestep are correctly represented, what you get is probably one point deviating from a representation of the originally (probably) smooth curve.

What you'd probably get, in other words, is high-frequency noise.

Does this sound plausible? Anyway, I retract my support for Russ's position regarding the probability of a bad CDR recording sounding brighter. Which is not to say that I'm now against him, but still

 

[MacDEF]

Quote:

Originally posted by robert_cyrus always burn as fast as you can, and use decent media.

I disagree; the faster you burn an audio CD, the greater chance of errors. I tend to burn mine at around 4x; any more and I've found that the CDs are less reliable on poorer-quality CD players.

 

[Tim D]

Jitter is FM distortion. It is most likely to affect higher frequencies(do the math, a frequency is a cycle per second, compare nanosecond 1x10^-9 inaccuracies in timing on 1/20 = .05secs compared to 1/44100 ~2x10^-5 secs). DAC's derive their clock from the signal, NOT the data...there is a difference. The signal carries the data, but the signal can be degraded, whereas the "data" as far as 0's and 1's remains intact, the time does not. A signal is a fluctuating electric quantity whose variations represent coded information (taken from the dictionary). Data is an abstraction of what is encoded in the signal. Time-based data is absent in SPDIF signals, the time-based data is derived from the signal as opposed to being data encoded IN the signal. Very few consumer DAC's reclock, *most* DAC's derive the a clock from the signal.

A frequency is cycles per time. Since time-based information is not carried in the data, but within a signal which can be degraded, the output audio can be degraded. It mostly affects higher frequencies. Why can't consumer products just add more digital buffers?

http://www.pcavtech.com/play-rec/summary/index.htm

That website also tests various CDR media and burn speeds as well as soundcards.

You can see the portable players which sport anti-shock (i.e. a data buffer) often increase jitter and produce high frequency noise. High frequency noise is often "glaring", and something that is "glaring" can induce the subjective response of "bright".

Bright is NOT an objective term. If you sit in your house all the time and go outside and things are "bright", it could be your individual response compared to someone who plays outside all the time. Saying that "brightness" is not a subjective term is like saying "hot" and "cold" are not subjective terms. Darkness is also a subjective term, and can also be accounted for by much more than just a reduction of treble energy. First of all it is only a qualititative term, and does not specify discrete values of any sort. That is why this subjective term applies to vision as well as sound. If I have an audio signal, I can reduce the lows and midrange, and the signal becomes brighter. This is because the highs are now relatively higher, but in absolute terms they did not change. If I were to alter the signal so it only occurs in one channel with a headphone with extreme channel seperation, again it will come across brighter. This will actually be a reduction of treble energy within one channel, yet it becomes psychoacoustically glaring for most, and hence will come across as brighter. If I add distortions and high frequency harmonics that are considered unmusical, again it is very easily possible that the subjective response of brightness can come up. If I were to use "brightness" only in the context of added treble energy, than perhaps it could be a more objective term. The fact is however, the person reporting brightness did not analyze his music through a spectrogram and point out elevated treble energy and say, "because there is elevated treble energy, the CDR's are brighter". He just said they were "brighter" after listening to them, and within the given context, it is clearly a subjective qualititative term that does not allude to any sort of derivable objective claims that jitter elevates treble energy. Another derivation of what the person meant by brightness was that something glaring appeared in high frequencies that was not there before. Elevated volume or amplitude is not the only way to produce a glaring effect.

Some portables with inadequate shock protection on indeed sounds tinny and bright(although a lot may depend on wheter the anti-shock is lossy, jitter distortion was measured to be much higher). Many portable headphones with terrible mismatch especially in high frequencies are also said to sound tinny and bright...it might not be because they have relatively excess treble energy, but that mismatch is incredibly poor. Some soundcards to some sound bright and tinny due to FM (frequency modulation) distortions. Poor 44-48-44 resampling on soundblaster cards for example is a type of FM distortion which adds high frequency noise. There are people that consider the sound as tinny and bright even though I would wager they are flat in EQ (besides the erroneous frequency peaks). Jitter is also FM distortion.

The fact that portables with added anti-shock buffers actually degrade jitter shows that you probably need expensive hardware design in order to actually introduce a buffer to reduce jitter or reclock the signal. Again an issue being power supply.

I will be getting the Panasonic 570 soon, and with its linear anti-shock mechanism, the only real variable difference between linear anti-shock and no anti-shock will be difference in jitter. If there is a real audible difference I will hear it with my Ety's, but honestly I don't expect to hear a very large difference if any.

This does not mean CDR burns will always induce more jitter...again it could actually be better, worse, or indistinguishable depending on your playback device, burner and burning settings/software, CDR media, and original media. This is only what I have said in my first post in this thread, and there is no reason to be so defensive that a CDR burn will always induce less desirable results. My only claim is a CDR burn can induce differing results of the audio signal when played back depending on different variables.

 

[beowulf]

Thought I would dig up this thread to add a few opinions.

a) Copies and Originals are not exactly perfect bit-by-bit duplicates. A CDR can indeed sound different from a pressed CD, even if the DAE process was absolutely perfect. (Think Jitter and clocking issues, which in some cases, might be enough to result in a slightly different analog output). I agree that in most cases, the difference is pretty close to zero.. inaudible.

b) Low speeds, including 2x and anything below 8x won't always mean higher quality. In fact, in many cases, lower speeds result in worse block error rates and jitter than high-speed copies.

c) DAE quality and accurate gaps/indexes determination, plus media quality are the most important factors, not really recording speed.

But if you don't agree, I'd like to hear your thoughts.

 

[bass man]

Quote:

Low speeds, including 2x and anything below 8x won't always mean higher quality. In fact, in many cases, lower speeds result in worse block error rates and jitter than high-speed copies

my CD have LESS ERROR if i burn them at 1x than at high speed 8X.

btw, i use a HP 8/4/32 burner

 

[Joe Bloggs]

Perhaps for your burner 4x is the optimal speed...?

 

[bass man]

Quote:

Got a CD burner? Not satisfied with the sound of your current headphone rig? Want to improve the sound of your rig at no cost? Send me a Private Message (PM)!

how do i PM you, Joe Bloggs? e-mail?