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Old 24th November 2003, 03:04 PM   #1
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Default analog CD de-emphasis

I have seen this touched on several times before, but never a completed design. I would like to implement the de-emphasis needed by a few CDs as an analog equalizer. My Musical Fidelity A3 24 DAC doesn't (can't) do it because of the upsampling. But, I have a tape monitor loop on my amp that could be used. This post De-emphasis states the time constants as 50Us and 15us, but I have no idea how to implement that as a simple op-amp based equalizer. This post
Thermionic Valve Analogue Stages shows a simple RC filter apparently from Thorsten Loesch. Could that be buffered by a couple of op-amps?

Thanks,
David
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Old 24th November 2003, 07:00 PM   #2
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Default This is how Philips did it........

Hope it makes sense..........

Jocko
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Old 24th November 2003, 07:48 PM   #3
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Default Re: analog CD de-emphasis

Quote:
Originally posted by net-david
...states the time constants as 50Us and 15us, but I have no idea how to implement that as a simple op-amp based equalizer.
It's simple. A design idea can be found here.

But before you start: The "feature" is VERY rare. The difference with the filter on and off isn't much. I suggest that you test it first and listen.

In my CD collection < 1000 CD's only 5 CD's have it and noone is newer than 1991.
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Old 25th November 2003, 01:01 AM   #4
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Thanks Jocko and peranders.

Is this about what I need?

Click the image to open in full size.

Any better schematic software you would recommend? This is my first attempt with eSketch. I suppose this should probably be another thread. Ironically, I work for an engineering firm with a ton of CAD software, but all intended to design highways and bridges.
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Old 25th November 2003, 01:08 AM   #5
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Default Yeah, except.........

That I would not use an op-amp as a unity gain buffer. They don't sound all that great, and a few are not unity gain stable. Just use a JFET to buffer it.

A lot of DIY guys use something called MicroCap. Basically, a simulation program, but who simulates???? Makes a good schematic drawing package. You can find it somewhere on the web: I did.

Jocko
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Old 25th November 2003, 01:32 AM   #6
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Thanks for the additional info.

I managed to click on the simulate button and came up with this:
Click the image to open in full size.

Actually looks right

Since I am a newbie, and have them, I'll probably try it with BUF634s. The DAC uses NE5532As, but has rather large output transistors, BDX33D & 34D.

--David
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Old 8th January 2009, 07:43 AM   #7
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All of you have probalby found solutions to your problems since this thread is very old.

I have a simple solution:

I own some Denon CDs (Mahhler symphonies conducted by Inbal, Frankfurt Radio Symphony Orch.).
I wanted to be able to play them on a CDP without the de-emp. possibility, so what to do?
At http://www.picosound.de/E_index.htm (at the bottom of the Download page), you can download a small program that is able to convert ripped WAV files back to normal condition.
Just rip track by track to WAV files and copy the WaveEmph.exe into the directory with the WAV files, open file by file in the program, check Apply De-emphasis, klick Modify and a few minutes later you are able to burn a CD with the music without emphasis.
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Old 8th January 2009, 08:03 AM   #8
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This problerm is very small as you might know, microscopic
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