| 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/show...t=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/show...t=cd+deemphasis 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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| Jocko Homo |
Hope it makes sense..........
Jocko |
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| peranders |
| 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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| net-david |
Thanks Jocko and peranders.
Is this about what I need?
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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| Jocko Homo |
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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| net-david |
Thanks for the additional info.
I managed to click on the simulate button and came up with this:
Actually looks right :D
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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