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Old 15th July 2003, 11:10 PM   #1
jwb is offline jwb  United States
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Angry De-emphasis

Which jerk invented de-emphasis? I'd like to go back in time and smack some sense into him.

Thank you,
jwb
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Old 15th July 2003, 11:14 PM   #2
SY is offline SY  United States
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Just curious: how many discs actually use it?
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Old 15th July 2003, 11:24 PM   #3
jwb is offline jwb  United States
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Nearly zero. That's why it is absurd that so many pins, registers, and datasheet pages are wasted on this subject.

"The CS3453243 includes a feature that can ruin the sound of any CD. Please make sure you write hundreds of lines of microcontroller assembly to ensure this feature is actually off."
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Old 16th July 2003, 02:39 AM   #4
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I wish it was nearly zero...

Some of the discs I have that have pre-emphasis:
- Glenn Gould, Goldberg Variations (Sony, 1981 version)
- Emma Kirkby collection (Hyperion)
- Several Sheffield Labs (Dave Grusin, Amanda McBroom)

I'm sure there are more, but these the Gould recording alone makes it indispensible.

I only paid attention when I started suspecting that a dac I had bought did not de-emph correctly. The designer did not implement, even though the chips were fully capable. Took me some *delicate* smt soldering to put in the connection required. Now I have a one-of-a-kind dac of this model that does de-emph correctly (automatically)!
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Old 16th July 2003, 03:17 AM   #5
jwb is offline jwb  United States
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It's just a nuisance, that's all. To properly handle de-emph in my new design, I need to bypass the sample rate converter and enable the de-emph on the digital filter when the receiver detects it. I also need to read the sample rate from the receiver to configure the filter, although if I assume the input sample rate of any de-emphasized stream is 44.1kHz, I should be OK.
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Old 16th July 2003, 07:43 AM   #6
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Quote:
Originally posted by SY
Just curious: how many discs actually use it?
I have 700 CD's and 10 have deemphasis. One of them is Roger Waters, "The pros and cons of hitch hiking"

Deemphasis was developed in times where 14 bit resolution was common and 16-bit was just only a dream. I don't understand the fuzz for a such small enhancment. I can switch on and off the feature with my DAC and the difference is huge

BTW: Americans the cover of the american cover has the behind of the girl covered with a black rectangle not the original european relase.

When I see this I think of USA a the main producer of porn. This was only a reflexion....
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Old 16th July 2003, 08:03 AM   #7
EC8010 is offline EC8010  United Kingdom
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Quote:
Originally posted by jwb
To properly handle de-emph in my new design, I need to bypass the sample rate converter and enable the de-emph on the digital filter when the receiver detects it. I also need to read the sample rate from the receiver to configure the filter,
Do what? Why don't you just implement de-emphasis as it was meant to be done - in the analogue domain? All you need is two resistors and a capacitor per channel. The time constants are 50us and 15us, so the upper resistor needs to be 2.33r times the lower resistor, and CR for the lower resistor and capacitor needs to be 15us (assuming zero source resistance and infinite load resistance).
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Old 16th July 2003, 08:18 AM   #8
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Why make it complicated, just use a modern DAC which does this rare filtering digitally.
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Old 16th July 2003, 09:20 AM   #9
EC8010 is offline EC8010  United Kingdom
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Default Complicated?

It sounded as though jwb was having to do a whole load of complicated digits, whereas the analogue solution is easy.
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Old 16th July 2003, 04:06 PM   #10
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Quote:
Originally posted by EC8010


Do what? Why don't you just implement de-emphasis as it was meant to be done - in the analogue domain? All you need is two resistors and a capacitor per channel. The time constants are 50us and 15us, so the upper resistor needs to be 2.33r times the lower resistor, and CR for the lower resistor and capacitor needs to be 15us (assuming zero source resistance and infinite load resistance).
Ah, that's an excellent idea! So I could just use a FET switch and the active-low EMPH output of the AES receiver to activate the filter. Of course I'd need four for balanced, but I like it.

Thanks a bunch.
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