analog CD de-emphasis

[net-david]

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 http://www.diyaudio.com/forums/showthread.php?s=&threadid=17775&highlight=cd+deemphasis 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
http://www.diyaudio.com/forums/showthread.php?s=&threadid=14598&highlight=cd+deemphasis shows a simple RC filter apparently from Thorsten Loesch. Could that be buffered by a couple of op-amps?

Thanks,
David

 

[Jocko Homo]

This is how Philips did it........

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

Jocko

 

[peranders]

...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.

 

[net-david]

Thanks Jocko and peranders.

Is this about what I need?

An externally hosted image should be here but it was not working when we last tested it.

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.

 

[Jocko Homo]

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

 

[net-david]

Thanks for the additional info.

I managed to click on the simulate button and came up with this:

An externally hosted image should be here but it was not working when we last tested it.

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

 

[klitgt]

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.

 

[peranders]

This problerm is very small as you might know, microscopic