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Old 4th July 2013, 07:02 PM   #9691
dvv is offline dvv  Serbia
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Quote:
Originally Posted by nigel pearson View Post
...

We use CD's to frighten the crows in our gardens . Crows are said to be intelligent, evil meets evil ? Hated in England as they eat people after the Black death . It's their job I beleive ? The crow is a great symbol of my love of CD .

...
Hence the British expression "Stone the crows"?
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Old 4th July 2013, 07:57 PM   #9692
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Originally Posted by fas42 View Post
Heavily compressed material replayed correctly is extremely aggressive sounding
for once we agree. some time ago foobar was on 'random' mode and it played a Judas Priest song from Painkiller. it was the first time I ever listened to that album on my current system. I know it by heart since I was a kid. but for the first time, the drums (and, unfortunetely, not only) sounded like modulated white noise. I stood there in awe. how come I did not hear it before with the previous systems? it sounded very different then. if someone told me 15 years ago something like that I would've called it snobbery but it now simply sounded unlistenable, not because of the music, but because of the sound.

Quote:
Originally Posted by nigel pearson View Post
I have a hunch no physical contact is not CD's best feature . Just think if USB sticks have been available . CD would never have happened . CD is a throw back to 1888 . Apparently pressing the disc was still No 1 priority when invented .
in all honesty, I have no idea what you're getting at.

Quote:
Originally Posted by nigel pearson View Post
Squarewaves from CD stop at about 1 kHz . The Fourier series needs about the 19 th harmonic in the sequence to be square . ( 44.1 /2 ) / 19 . Such a wave looks like an amp with mild ringing . Slew rates ??????? Where , when , how ? To restate my case . Slew rates matter . It is simple current to drive the VAS . There is no music that demands it . If it were not so tweeters would last minutes .
first. you said it yourself that slew-rate is not necessary because it exists in music. how come you also used the slew-rate (more below) of the signal present at the input as an argument for the fact that CD is wrong?

second. can you explain the "44.1 / 2" thing? a perfect (in the mathematical sense) step requires infinite bandwidth. that waveform looks like an amp with ringing because of the Gibbs phenomenon. had you seen no Gibbs, it would be really weird and definitely abnormal. a square wave can't look like a square wave (given you zoom in enough) if you band-limit it. you see that ringing because a perfect step would need infinite bandwidth. and because (as far as current science goes) human hearing does not require infinite bandwidth and RedBok is based on that.

third. with CD you can have slew rates exceeding what is naively suggested by the inter-sample delay. actually, ~3 times larger with RedBook. incredible as it may seem, with properly implemented digital you can actually have all the slew rate that a perfect (again, in the mathematical sense) full scale 20kHz sine needs. it all depends on the implementation. maybe you don't believe me, I'm attaching a screen shot of a generated 20kHz wave in CoolEdit. look at the green squares: those are the sample values. nowhere near sine, innit? in fact it's "oh my, what is that rubbish!". then look at the continuous line. I'll be... a sine! how do you explain that? sinc interpolation, that's what you're looking at.

now... if you tell me that there are psychoacoustic reasons why a LPF @20k is not enough, you do have a case. if you tell me that the reconstruction filters are not always perfect, you do have a case. if you tell me that dither can be a bad thing if done uwisely, you do have a case. but that's totally different from your arguments above.

it's incredible the amount of times we can go round and round and round in circles with this.

of course, all the above is accepting that we don't move within the paradigm of "I still believe it", because, if that's so, we could as well just close the whole forum.
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Last edited by mr_push_pull; 4th July 2013 at 08:02 PM.
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Old 4th July 2013, 10:32 PM   #9693
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Some people need to watch this: https://www.xiph.org/video/vid2.shtml

Can anyone point to any reputable experiment that shows that CD is anything less than transparent? I can point to an AES paper that says it is transparent:

Quote:
Claims both published and anecdotal are regularly made for audibly superior sound quality for two-channel audio encoded with longer word lengths and/or at higher sampling rates than the 16-bit/44.1-kHz CD standard. The authors report on a series of double-blind tests comparing the analog output of high-resolution players playing high-resolution recordings with the same signal passed through a 16-bit/44.1-kHz “bottleneck.” The tests were conducted for over a year using different systems and a variety of subjects. The systems included expensive professional monitors and one high-end system with electrostatic loudspeakers and expensive components and cables. The subjects included professional recording engineers, students in a university recording program, and dedicated audiophiles. The test results show that the CD-quality A/D/A loop was undetectable at normal-to-loud listening levels, by any of the subjects, on any of the playback systems. The noise of the CD-quality loop was audible only at very elevated levels.
https://secure.aes.org/forum/pubs/journal/?ID=2
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Old 4th July 2013, 11:16 PM   #9694
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Originally Posted by dvv View Post
In fact, some terrific specs scare the hell out of me. For example, when a power amp is specified with a THD of say 0.001% at full blast - I immediately start wondering whether its global NFB is 60, 80 or more dB
If I was asked to assess in a couple of minutes how good a power amp was I would immediately put on a CD of high energy rock with very dominant, clear cymbal content, and wind up the wick, all the way. This would tell me straightaway whether it had decent chops, and was worth worrying about - only recently have I seen standard amps do a half decent job here ...
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Old 5th July 2013, 05:14 AM   #9695
hpeter is offline hpeter  Europe
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Quote:
Originally Posted by nigel pearson View Post
I have a hunch no physical contact is not CD's best feature . Just think if USB sticks have been available . CD would never have happened . CD is a throw back to 1888 . Apparently pressing the disc was still No 1 priority when invented . Making Cassettes was a fools game. Expensive and less than excellent . They were not going to repeat that mistake . CD , BS that lasts for ever . Even the last bit was lies .

do you remember first flash mp3 players ? thomson, sony, panasonic? 64 and 128MB ! types, costed arm and leg!

today you will receive 512MB usb disk as free advertising gift.....
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Old 5th July 2013, 06:33 AM   #9696
dvv is offline dvv  Serbia
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Originally Posted by hpeter View Post

do you remember first flash mp3 players ? thomson, sony, panasonic? 64 and 128MB ! types, costed arm and leg!

today you will receive 512MB usb disk as free advertising gift.....
Right, but I don't see where's the surprise?

We've been seeing the same effect in PCs forever. Memories start off as expensive and drop to rock bottom prices, and that's when the industry invents a different type of memory to get its profits back up again.

Old hat.
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Old 5th July 2013, 07:21 AM   #9697
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Originally Posted by nigel pearson View Post
CD is just about OK . 1972 BBC/Nippon Nicam was and is better
Why do you say that? NICAM was only 32 ksps, so 15kHz is about the absolute upper limit
It uses a 14 bit 10+4 structure, so in any data block you only get 10 bits of resolution. This is marginal for low level detail in a frequency band far from a strong signal which is at a frequency where the ear is insensitive
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Old 5th July 2013, 09:04 AM   #9698
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Mr Push Pull .

44.1 kHz is the sampling frequency . Divide by 2 to get Nyquist theoretical maximum frequency . 22.05 kHz . Leap of faith now . The Open University taught that the 19 th harmonic ( 1/19 F 19 ) is required to get a reasonable square wave . The series is infinite as we know so I am being generous to say we might get a 1 kHz square wave out of a CD . Seeing as 10 kHz square-waves were routinely possible from transistor amps circa 1964 it is interesting that digital allowed us to think it unimportant .

I agree rise time can be very good on CD . However for various reasons we can not record any signal we want even within the supposed bandwidth . To say we don't reduce rise time significantly is correct and is the saving grace of CD . Off set this will typical energy levels at 20 kHz to say in reality it is not a big problem .

My objection to slew rates is that music does not demand it . Other poorly explained mechanisms are working . They are far from unimportant . As Douglas Self said these things show up in other measurements when less than ideal . One commenter said both SACD and MC pick up have signals that require high slew rates . I totally doubt that . The fact the VAS needs current is fine . Call it current starvation and I might start to beleive it . I remember about a week going by and a great agreement on slew rates was reached . I sat back and thought and who really said why . Lets be clear I design as all do . I am jut not comfortable that we say it is true because we say so . I will throw in a suggestion . Make an amp with compromised slew rate . Listen and find it sounds constricted . Input filter it . Does it suddenly sound great allowing for lost sparkle . I bet it doesn't .

1888 . Berliner found a cheap way to quickly make copies of recorded music . People may not realize that this fact alone is the big deal for mass production . CD needed that speed of production . Old dogs , new tricks ?
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Old 5th July 2013, 09:29 AM   #9699
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Originally Posted by davidsrsb View Post
Why do you say that? NICAM was only 32 ksps, so 15kHz is about the absolute upper limit
It uses a 14 bit 10+4 structure, so in any data block you only get 10 bits of resolution. This is marginal for low level detail in a frequency band far from a strong signal which is at a frequency where the ear is insensitive
We always called it 13 bit . Doubtless you are correct . When learning about it there was no internet and the library didn't really have much on it . Hi Fi News was good as it got , they didn't go into working detail . One must remember computer speak is common now , not so then . We had no point of reference . I seem to remember the BBC saying that they were very surprised Philips never contacted them about digital . The BBC tests if I understand correctly were done using expert listeners . All of this data would have been shared with Philips if they had asked . Doubtless the man-hours devoted to it were considerable . I have to say Nicam is so good as to make me doubt I can hear it in use most of the time if not using a larger than life volume . When one considers it has 15 kHz on a good day . Then a Brick-wall filter to get rid of the 19 kHz pilot tone . Next the mind boggling circuits if 1972 , it is the miracle CD never was . The magic of the BBC research was to know what compromised could be used and ones that couldn't . Pumping effect was deemed to be OK as the volume needed to hear it would be excessive . Also most systems were well into noise by then . I would guess the BBC had 20 dB between digital effects and the noise of the best put together program material . I wonder if the BBC knew of noise dither ?I bet they did ?

I guess I never realized the move to 14 bit was when the Near Instantaneous label was first used . In principle I feel it was the same system albeit better .

The BBC PCM / NICAM Story

Last edited by nigel pearson; 5th July 2013 at 09:34 AM.
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Old 5th July 2013, 09:58 AM   #9700
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The BBC used to transmit FM around the country as a digital signal and analogued it at the transmitter. The digital signal was a companded 14bit 15kHz.

This when we listened to FM sounded good (sometimes very good). We generally did not know that we were listening to a 14bit digital signal. We were after all listening to the BBC's FM radio.

Very much later Nicam (for television sound) was brought in.

I suspect they adopted the same companded 14bit simply because it already existed and it was already accepted as providing a very good quality when the BBC did it right.

The difference between FM radio and Nicam is that the analoguing of the digital signal is done at the transmitter for FM and we have it done inside our (build down to a price) compromised TV dacs.
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