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Pre-emphasis in CD recordings & CD Players

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Rabepobemababe

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It has been reported that some otherwise well regarded DACs can make some genuine audio CD recordings sound harsh, not because of any shortcoming on the DAC's part per se, but because of the separate transport + DAC arrangement lacking a filter to remove pre-emphasis in some audio CDs which had been recorded with a pre-emphasis of frequencies around 10 KHz. It is said that there is a 'PRE' tag in the beginning of such audio CDs, which is detected by dedicated audio CD players (which have a "de-emphasis" function built in) and compensated for.

If this is so, isn't a dedicated audio CD player a surer way to better sound than using a DVD player as transport along with an external DAC?

How common is this 10 KHz "pre-emphasis" in audio CDs?
 
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sound_cycle

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It has been reported that some otherwise well regarded DACs can make some genuine audio CD recordings sound harsh, <snip>t is said that there is a 'PRE' tag in the beginning of such audio CDs, which is detected by dedicated audio CD players (which have a "de-emphasis" function built in) and compensated for.

Could you link please?

the (digital) transport delivers a bitstream, hopefully unmassaged, to a DAC where the rest bappens. Or so I thought.

ciao
gr
 

Rabepobemababe

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From Wikipedia:

"Pre-emphasis on audio CD

Some early digital recording & playback equipment, including CD players, used 14-bit converters, even though they were dealing with 16-bit audio. Some also used noisy "brick wall" filters to remove frequencies higher than the Nyquist frequency (22050 Hz). The resulting noise introduced by these converters and filters could be made relatively quiet by using pre-emphasis: boosting the signal (especially the higher frequencies) in the recording before it was put onto CD, and embedding flags in the disc's subcode to tell a CD player to apply de-emphasis on playback. Some CD players even had a de-emphasis button that could be used to manually apply de-emphasis, but now it's just a built-in feature of the analogue outputs of nearly all dedicated audio CD players. By the late 1980s, pre-emphasis stopped being used because reliable 16-bit DACs with oversampling and other technologies minimized the conversion & filtering noise without the need for pre-processing the recording. Most major-label CDs with pre-emphasis were manufactured in Japan in the early and mid-1980s. Relatively recent forum posts indicate that pre-emphasis is still used on newly manufactured CDs by some indie labels, mainly for classical titles. A pre-emphasis flag for each track is normally stored in the subcode along with the audio data. It's also supposed to be stored in the table of contents (TOC), but many CDs have TOCs that say there's no pre-emphasis when in fact the subcode says there is. There are also some CDs which people believe were mastered with pre-emphasis, but which have no pre-emphasis flags set at all."


Even though Wikipedia says that audio CDs with pre-emphasis stopped in the 1980s, truth is that some audio CDs released as late as early 2000s still had pre-emphasis applied during recording.

Here is a post from a gentleman on Head-Fi, which explains the problems better:

"I had to learn about ripping CDs that have pre-emphasis a few months ago when I bought an original issue C2K version of "The Wall". I ripped it and played it and it didnt sound right. Played it on a home stereo system and it was good. Played it on the computer from the DVD drive and it sounded wrong. Played the rip and it sounded wrong. What was going on? So began my journey. CD emphasis was implemented in order to get better linearity in the high-frequency range given the capabilities of old school A/D and D/A converters. The CD gets mastered with pre-emphasis and a flag indicating pre-emphasis is present. At playback the DAC applies de-emphasis. Pre-emphasis adds a high-frequency boost. De-emphasis applies a complimentary high-frequency cut to get the signal back to flat. There is a good explanation of CD emphasis in an article at audioXpress OnLine. The article is in their PDF archive. Direct linking to the PDF file doesn't work so go to the PDF archive and search for "A De-Emphasis Test CD" by Gary Galo. Ripping a CD bypasses the DAC in the CDR drive and since it is the DAC that is responsible for applying de-emphasis, the de-emphasis doesn't get applied unless the ripper software does it. A few older rock CDs from the 80s have pre-emphasis. A larger number of classical music CDs from the 80s have pre-emphasis and some classical releases today continue to have pre-emphasis. If you have a collection that includes classical music you likely have a few CDs with pre-emphasis. In my collection of classical music I found that most of the BIS recordings had pre-emphasis, a few of the Delos recordings had pre-emphasis, a Deutsche Grammophon and a Telarc had pre-emphasis."

Steve Hoffman Music Forums have an interesting discussion on the subject, and an actual test figures on how much the higher frequencies are attenuated in the "de-emphasis" process by a dedicated Sony Audio CD player:

http://forums.stevehoffman.tv/threads/cd-dat-with-pre-emphasis-how-to-de-emphasize-correctly.88541/


My own discovery of the phenomenon (which has been quite a revelation for me) came after my Denon DCD 700AE went bad. I was playing a genuine Eric Clapton CD on a DVD player (as transport) coupled with an external DAC (connected to the digital out of the DVD player). I was surprised at the unusually harsh sound of an audio CD which hitherto always sounded good. I was sure that nothing was wrong with the DAC. It was not the case with all the audio CDs either. While researching this, I stumbled upon this "pre-emphasis" thing.

Since some DACs chips (in both internal & external DACs) have de-emphasis algorithms built-in, and some do not, and in view of the fact that even those DACs with built-in de-emphasis would employ differing algorithms to do the job, does it not mean that based on the properties of the audio CD being played, and those of the DAC chip being employed, the sound will be different in each case?
 
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