Vic, that makes zero sense, theoretically or otherwise, from anything known about polymer processing. Or anything known about chemical/physical processes and rates (Arrhenius, anyone?).
There's a big difference between "some people hear a difference" and "some people claim to hear a difference."
There's a big difference between "some people hear a difference" and "some people claim to hear a difference."
SY,
I'm not a polymer expert. I'm just relaying the arguments that I heard. I try to be as open minded as possible.
I personally think that a neat test would be to microscopically look at a CD, freeze it then look at it again. If there is no discernable difference, then the freezing process would be DIY snake oil. Unless, of course, people here differences. But, again, people say they hear differences for a lot of reasons. Some of which should make no physical sense at all.
I'm not a polymer expert. I'm just relaying the arguments that I heard. I try to be as open minded as possible.
I personally think that a neat test would be to microscopically look at a CD, freeze it then look at it again. If there is no discernable difference, then the freezing process would be DIY snake oil. Unless, of course, people here differences. But, again, people say they hear differences for a lot of reasons. Some of which should make no physical sense at all.
Polymers are one of the few things I do claim to be an expert at (my Ph. D. dissertation was specifically about the interaction of polymers with infrared light), and I can assure you that these arguments are doo-doo, to be kind. You may well see some differences between a pre and post freezing CD, but they'll have more to do with the shock of the treatment than anything else and they won't matter a bit (ouch, bad pun) to what the laser does.
The true test is one in use; if I give someone 5 discs that were frozen and 5 discs that weren't, can he reliably tell me which is which by listening or measurement of the CD player waveforms? When someone runs that test properly and reports the results, and the results hold up to replication, then it's worth doing some serious investigation. Until then, you should consider this as one more example of the voodoo that has poisoned high-end audio.
The true test is one in use; if I give someone 5 discs that were frozen and 5 discs that weren't, can he reliably tell me which is which by listening or measurement of the CD player waveforms? When someone runs that test properly and reports the results, and the results hold up to replication, then it's worth doing some serious investigation. Until then, you should consider this as one more example of the voodoo that has poisoned high-end audio.
vic said:
Like putting a photograph of your audio system in the freezer to make it sound better?
Peter Belt has been proving this for years now. You can't get more outlandish than what Belt has been selling over the years, yet there are many people who swear by it.
Because there is so much psychology involved in our perception of sound, you can offer up literally anything. Just make something up out of thin air. It doesn't actually have to do anything, yet if you get people to try it, you'll always find a good number of people who purport it to have made a significant improvement.
If you want a good laugh (and further proof that you can dream up literally anything at all), check this out:
<a href="http://www.belt.demon.co.uk/whatamess.html">WHAT A MESS!!!!--An alternative view of reality</a>
se
Henckel said:
Hi
The master clock ofcourse is the same (though still contains too much jitter)
The above described fifo works fine but has limitted atenuation.
Starting with about 10 to 20 ns pit jitter (depending on drive, media etc) still too much jitter will ripple through.
If not sufficiently attenuated, it will obviously lead to distortion at the actual D to A conversion, which ofcourse is audible.
Besides that, different media are different (!). This may lead to
- different pit jitter values
- different behaviour of the servo's of the playback module (which induces different jitter as the hardware of most CD players is not carefully designed)
- different jitter patterns due to different prints at the top of the disc
etcetera
Different discs / copies / prints or whatever very likely sound different. Those not able to hear the differences are lucky, they can stick with cheap CDR's and writers, and do not mind buying print nr 1 or nr 10.000 from their popular artists.
Needless to state that CDRW discs sound better than CDR's as the RW media is far less critical towards writing power and write strategy.
best regards
Hi,
Here is some interesting reading:
http://www.exactaudiocopy.de/eac13.html
http://www.cdrinfo.com/Sections/Articles/Specific.asp?ArticleHeadline=Jitter Tests&Series=0
Here is some interesting reading:
http://www.exactaudiocopy.de/eac13.html
http://www.cdrinfo.com/Sections/Articles/Specific.asp?ArticleHeadline=Jitter Tests&Series=0
Pjotr said:Hi,
Here is some interesting reading:
http://www.exactaudiocopy.de/eac13.html
http://www.cdrinfo.com/Sections/Articles/Specific.asp?ArticleHeadline=Jitter Tests&Series=0
Hi
Here is another one
http://www.cdrinfo.com/Sections/Articles/PrinterFriendly.asp?ArticleHeadline=Writing+Quality
for those who do not know me: I design Optical PickUp units for recordable DVD players and drives at Philips Optical Storage.
best regards,
Hi,
We must not confuse the various kinds of jitter. There is pit jitter at the readout/writing mechanism of the CD reader/writer and there is jitter of the conversion clock at the DA converter. If pit jitter becomes severe this leads unavoidable to readout errors in the digital domain. You get simply wrong data samples. The error correction mechanism handles this and it depends on many factors how well these errors will be corrected and/or concealed.
The other mechanism is jitter of the conversion clock at the DA converter. You can have a complete error free data stream red from the CD, the DA conversion clock jitter still has its audible impact.
Pit jitter does not necessarily degrade DA conversion clock jitter in a well-designed CD/DVD player.
Both jitter mechanisms are completely different but both have their own impact on the final audio quality.
We must not confuse the various kinds of jitter. There is pit jitter at the readout/writing mechanism of the CD reader/writer and there is jitter of the conversion clock at the DA converter. If pit jitter becomes severe this leads unavoidable to readout errors in the digital domain. You get simply wrong data samples. The error correction mechanism handles this and it depends on many factors how well these errors will be corrected and/or concealed.
The other mechanism is jitter of the conversion clock at the DA converter. You can have a complete error free data stream red from the CD, the DA conversion clock jitter still has its audible impact.
Pit jitter does not necessarily degrade DA conversion clock jitter in a well-designed CD/DVD player.
Both jitter mechanisms are completely different but both have their own impact on the final audio quality.
Pjotr said:
Hi Pjotr
Thanks for your reply. Yes you are rigth, too high jitter leads to real errors.
I am very aware of clcok jitter and its' impact (I have my own clocks made on specification) and we desigend a DAC:
http://members.chello.nl/~m.heijligers/DAChtml/dactop.htm
which takes care of jitter to a great extent
Your statement is right, a wel designed player is insensible to incomming jitter. I have yet to see this player.....
In many players the servos affect the playback quality as they induce jitter, regardless of the clock quality.......
best regards
SY said:
Hi
The DAC design in my previous link has a diagnostic output, described in the schematics
http://members.chello.nl/~m.heijligers/DAChtml/dig_r2c.pdf
and here:
http://members.chello.nl/~m.heijligers/DAChtml/PLL sound.htm
It is a demodulated output which makes it possible to hear the jitter. One of the things you can hear in a badly designed CD player is the spindle motor.......
enjoy
Guido
I guess my question wasn't clear. Think of the CD system as a black box. In one end, I put in some data. At the other end I recover an analog signal which goes off to the rest of my stereo system. That's the output I'm talking about.
I'm very curious as to how much, with real world systems, do we see actual measurable differences in the recovered analog signal with things like various bit-for-bit copying schemes and normal variations in CDs and CD playback.
I'm very curious as to how much, with real world systems, do we see actual measurable differences in the recovered analog signal with things like various bit-for-bit copying schemes and normal variations in CDs and CD playback.
Hi Guido,
You are right when it comes to a separate DAC where the DA clock must be recovered. ( No I don’t want to go into a discussion about asynchronous clocking, that belongs to another thread IMHO.)
What I mean by “Pit jitter does not necessarily degrade DA conversion clock jitter in a well-designed CD/DVD player.” is the following: In a “one in all CD player” there is one master clock. That clock goes two ways, it goes a way to the DA converter to clock de DA conversion and it goes away to control the readout mechanism of the CD. It makes sense to put in an “low jitter clock” regarding the DA conversion. I don’t see that in this case the pit jitter degrades the DA converter clock. OK a badly designed CD player … but then there are many complex interactions like feedthrough by PSU lines, gnd loop problems etc.
BTW My compliments for your well documented links
You are right when it comes to a separate DAC where the DA clock must be recovered. ( No I don’t want to go into a discussion about asynchronous clocking, that belongs to another thread IMHO.)
What I mean by “Pit jitter does not necessarily degrade DA conversion clock jitter in a well-designed CD/DVD player.” is the following: In a “one in all CD player” there is one master clock. That clock goes two ways, it goes a way to the DA converter to clock de DA conversion and it goes away to control the readout mechanism of the CD. It makes sense to put in an “low jitter clock” regarding the DA conversion. I don’t see that in this case the pit jitter degrades the DA converter clock. OK a badly designed CD player … but then there are many complex interactions like feedthrough by PSU lines, gnd loop problems etc.
BTW My compliments for your well documented links
Pjotr said:Hi Guido,
You are right when it comes to a separate DAC where the DA clock must be recovered. ( No I don’t want to go into a discussion about asynchronous clocking, that belongs to another thread IMHO.)
What I mean by “Pit jitter does not necessarily degrade DA conversion clock jitter in a well-designed CD/DVD player.” is the following: In a “one in all CD player” there is one master clock. That clock goes two ways, it goes a way to the DA converter to clock de DA conversion and it goes away to control the readout mechanism of the CD. It makes sense to put in an “low jitter clock” regarding the DA conversion. I don’t see that in this case the pit jitter degrades the DA converter clock. OK a badly designed CD player … but then there are many complex interactions like feedthrough by PSU lines, gnd loop problems etc.
BTW My compliments for your well documented links
Hello Pjotr, others,
Pit jitter indeed may ripple through the DACs due to many possible kinds of crosstalk, therefor again, lower jitter means lower reidual artefacts.
Ofcours one may argue where to improve the whole chain, the answer being driven by cost and technical feasibility.
I do not understand asynchronuous clocking sufficiently, in our DAC we designed a cascaded PLL which works very well: Its' immunity for jitter on the SPDIF signal is the highest I have seen among commercial DACs I measured on. Still I can hear differences in transports, therefor the least one can do is reclock the SPDIF signal, using the same low jitter clock.
Thanks for your kind words about our DAC web page and the links.
all the best
AMT-freak said:
Hi AMT freak, others,
I have not used ASRC's (yet)
Can someone explain how and at what cost, a difference in the time domain is being dealt with by ASCR's ?
Be suspicious with respect to the outgoing data of these chips: Their jitter is too high, reclocking is advised !
all the best
I'm not an expert in DSP, but as far as I understood it, an ASRC is basically a standard oversampling circuit (including a digital filter) that outputs the signal at a very very high fs. In the output section of the ASRC, the very very high fs signal is digitally re-sampled with a much lower, locally generated master clock. Theoretically, the output timing is completely independent (as the "A" in ASRC implies) from any clock signals (and hopefully their associated jitter) before the ASRC.
Doesn't this sound great?
Actually, it's totally different and the "very very high fs" thing is only a model to easier understand the complicated DSP algorithms that are applied to the signal in an ASRC. I still have to look into this.
The CS8420 datasheet has some more info on the subject:
http://www.cirrus.com/en/pubs/proDatasheet/8420.pdf
Of course I understand that the complicated ASRC circuit might introduce even more jitter which could render its benefits totally useless. I'll know more when I have finished my digital pre project.
Doesn't this sound great?
Actually, it's totally different and the "very very high fs" thing is only a model to easier understand the complicated DSP algorithms that are applied to the signal in an ASRC. I still have to look into this.
The CS8420 datasheet has some more info on the subject:
http://www.cirrus.com/en/pubs/proDatasheet/8420.pdf
Of course I understand that the complicated ASRC circuit might introduce even more jitter which could render its benefits totally useless. I'll know more when I have finished my digital pre project.
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