De-emphasis

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jwb

jwb

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Joined 2002
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."
 
M

mb

Member
Joined 2002
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)!
 
jwb

jwb

Member
Joined 2002
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.
 
peranders

peranders

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Joined 2002
sjostromaudio.com
Paid Member
SY said:
Just curious: how many discs actually use it?
Click to expand...
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 :no:

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

When I see this I think of USA a the main producer of porn. This was only a reflexion....
 
EC8010

EC8010

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Joined 2003
jwb said:
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,
Click to expand...

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).
 
jwb

jwb

Member
Joined 2002
EC8010 said:


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).
Click to expand...

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. :drink:
 
Z

Zombie

Member
Joined 2003
Remove de-emp in Quad 67CD?

Interesting...got a Quad 67CD with a CS4328 DAC.

Between the lowpass filter and the opamp (an OP275), there's a 1k5 and a 10nF cap and a FET to ground.
The base of the FET is connected to a TLC272 opamp output (guess the FET is shorting the R anc C to ground...)
The R, C and FET to ground is preceeded by a 3k4 resistor in series and a C of 470pF to ground

What can I acheive by removing the de-emp? Should one remove those components altogether or just lift out the first leg of the R in the de-emp?

Cheers
Tom
P.S. What about the OP275, can I leave it in or is it worthwhile to use smth else?
 
lauret

lauret

Member
Joined 2007
EC8010 said:


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).
Click to expand...


I was planning to use a unused input in my pre-amp for cd's with pre-emphasis. Is it possilble to parallel the DAC output to another input and put this filter between the input selector and the DAC output?

And what are supposed to be the values of this RC-circuit? Is this a normal low pass filter with a resistor in series and a capacitor in parallel?

Thanks, so I can listen to Gould's Goldberg variations again.
 
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