My Lumin X1 has this ´´De-Emphasis ´´ for 44KHz CD
But I have never used it. Don’t know if it makes a real improvment .
Learned something new today and it isn't good.
I have been in this crazy hobby for over five decades and thought I knew most of the basic information regarding audio quality.
That was before this morning.
Today I learned about the practise of applying "pre-emphasis" to CDs that was around during the late '70's and early '80's. Apparently this practise was developed as a way of reducing the signal to noise in digital audio. The problem is this was a two-part process and required the CD player to have a "de-emphasis" capability to allow the disk to play properly. Without the application of de-emphasis, cd's would sound "bright".
My question would be, "Does everyone else know about this?"
If you do, "How do you deal with it?"
I still listen to CDs and this is not something I need in my life.
My Lumin D1 has it as well, but it is not an automated function. If you have a CD that requires "de-emphasization" you need to turn the function on in the software.
I know it has stopped. My concern is that many of the best quality CDs from that era are pre-emphasized. Specifically many Japanese versions.
@tony1954 does your CD player have the de-emphasis circuitry? If it doesn't, then those CDs will sound a little bit bright.
I have been trying to find out, but so far no luck.
I have the Cambridge Audio CXC transport.
Well, it was to INCREASE the signal to noise. As I recall it had something to do with the early anti-aliasing filters not being great. AFAIK, any CD player should automatically detect and enable/disable the matching de-emphasis as should most audio playback systems. However it's imperfect. According to this, it's not on a lot of CD's so maybe you don't care??
I have an old tube DAC that has de-emphasis circuitry and an indicator light when a CD has pre-emphasis. Only a few classical CDs in my collection made this indicator light go on; maybe I don't listen to those anymore, but I haven't been troubled that my subsequent DACs lacked this circuitry.
If you think you want a DAC with the de-emphasis circuitry, I'd be willing to sell my Anodyne ATAS. It was working fine last time I used it. When I bought it in the 1990s, it sounded better than a well-reviewed Wadia DAC I compared it to in my system. The ATAS cost $3000 then. I've intended to put it up for sale, but just haven't gotten around to it. IIRC, it only goes up to 48kHz, so it won't work for today's high-res files. But it will give CDs some nice tube warmth.
Please don't ask me to explain this in any more detail as I will already be pushing the limits of my knowledge. Use Google if you want to learn more.
Nyquist rate DACs have a zero-hold structure. They are not flat to 20KHz and roll off towards 20KHz. A zero-hold means it holds the same value between sample updates. I understand ADCs don't normally have this issue because they take a snapshot in time. To compensate for this roll-off, the CD could have pre-emphasis to compensate and get a flat response. The roll off is not very big. When up sampling DACs became standard, this was not needed as the roll-off at 20KHz was very small.
The redbook CD standard has a flag on the CD that says pre-emphasis was applied. The CD player should read this and tell the player what it needs to do if anything.
Pre-emphasis is the first part of a noise reduction technique in which a signal's weaker, higher frequencies are boosted before they are transmitted or recorded onto a storage medium. Upon playback, a de-emphasis filter is applied to reverse the process. The result is a higher signal-to-noise ratio (SNR); the original frequencies are restored, but noise that was introduced by the storage medium, transmission equipment, or analog/digital conversions is quieter than it would have been if no filtering had been done. Pre- and de-emphasis can be collectively referred to as just emphasis.
Emphasis was sometimes used in digital storage media in the late 1970s through early 1980s, including on a small percentage of audio CDs. Emphasis is akin to Dolby noise reduction for tapes, or the RIAA equalization curve for vinyl records.
From what I gather emphasis was implemented to try to improve the sound of the CD players, not the cd's themselves. This is a case where the media was better than the technology to play it.
Pre-emphasis is very likely dead IMHO, because ripped CD's data doesn't carry pre-emhpasis bit. A lot of people use servers and music with pre-emphasis would sound bad (+9.5dB@20kHz) without de-emphasis. Some ripping programs might contain plug-in to de-emphasis if needed. There are programs (like SoX) to de-emphasis digital data, but it is additional hassle (to find out if it is needed and convert every song).
This has nothing to do with noise or noise reduction. Why does that keep getting repeated??
It was a necessary step to deal with the natural operation of early DACs.
One of my colleagues sent this. It is not light reading but the concept seems easy to understand.
Thanks. Nice to get a response that is based on actual research and facts, as opposed to a lot of guesses and hypothesizing.
Researching information about any topic.
Wasn't that what Google was for, before they tried to take over the world?
The other thing that is kind of along these lines was HDCD decoding. I don’t know of any (and I haven’t searched) ripping software which would detect and expand an HDCD Redbook 44.1 / 16 to 44.1/24 so I ended up writing some hack based on old Microsoft C code.
HDCD was also weird in that sometimes the HDCD flag was on, but no HDCD features were actually used.
All this just underlines the difficulty of re-creating an accurate and satisfying sound once you break up the signal into billions of pieces. And the lengths you have to go to in corrupting the sound further in an effort to undo the undoable.
The old omelette question for digital engineers. Their work has achieved a lot in 40 years but dither will always be with us.
I don't know what this has to with the topic.
Emphasising was something record engineers did to manipulate the frequency curve to make up for the deficiencies playback equipment half a century ago.
Digital sound quality today is for the most part fabulous and all the discussions about it on this site usually involve tweaking sound, not major surgery.