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Old 25th May 2006, 05:32 PM   #11
banana is offline banana  Hong Kong
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Bernhard, thanks for the file. Which kind of dither is it?

Lower noise floor might be good thing, but I'm affraid there's no chance for us to enjoy 24bit audio source in foreseeable future.....
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Old 25th May 2006, 05:35 PM   #12
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Quote:
Originally posted by banana
There's more if you can read Chinese. My next target is UCD400 and Manger active 2-way, but it already took me to long to build.

Damn! I knew I should have learned Chinese. Good choices, though. I've looked into those as well, but the Mangers are definitely out of my price range.
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Old 25th May 2006, 05:36 PM   #13
banana is offline banana  Hong Kong
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PCB view. Resistors are 1206 size.
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File Type: jpg ad1853 pcb dir.jpg (73.8 KB, 657 views)
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Old 25th May 2006, 05:59 PM   #14
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Quote:
Originally posted by banana
Bernhard, thanks for the file. Which kind of dither is it?

Lower noise floor might be good thing, but I'm affraid there's no chance for us to enjoy 24bit audio source in foreseeable future.....
No idea what kind of dither. I did not make it, look at the link address.
Please measure

16bit data + os filter + >16bit DAC also gives lower noise floor.
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Old 3rd August 2006, 03:53 PM   #15
banana is offline banana  Hong Kong
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Bernhard,

It's been a long time..... here it is the -60dBFS FFT.

I didn't use the test tone you suggested. I use digital signal from AP instead, 16bit -60dBFS trianglar dither.

Bascially, everything hides below noise floor.
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File Type: gif ad1853 -60db.gif (12.8 KB, 459 views)
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Old 3rd August 2006, 03:57 PM   #16
banana is offline banana  Hong Kong
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To have better view of harmonics, I applied 32 times averaging and do the -60dB FFT again.

K3 now appears, and also a tiny bit of K5.
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Old 4th August 2006, 08:12 AM   #17
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Quote:
Originally posted by banana
To have better view of harmonics, I applied 32 times averaging and do the -60dB FFT again.

K3 now appears, and also a tiny bit of K5.
Hi Banana,

Your results appear very good, even considering use of the
OPA2604 which isn't the best of opamps.

I recommend you try some OPA627's. The measurements
-may- improve but the sound definately will.

Is this with 1853 in mono or stereo mode?

Cheers

Terry
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Old 4th August 2006, 08:42 AM   #18
banana is offline banana  Hong Kong
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Hi Terry,

The AD1853 is in stereo mode, that is one single chip for both left and right.

Thanks for the opamp suggestion
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Old 4th August 2006, 09:32 AM   #19
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Hi Banana,

thanks for posting the graphs, looks good which is expected from a quality delta sigma DAC.
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Old 4th August 2006, 02:02 PM   #20
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Quote:
Originally posted by Bernhard
Hi Banana,

thanks for posting the graphs, looks good which is expected from a quality delta sigma DAC.
Bernard,

These are delta sigma but they are, from memory, 5 bit unity weighted.
So out of band noise is much better than the old 1 bit designs.

They also have proper ciurrent sink OP as opposed to SCF that
Cirrus and AKM uses. I like the AD approach better, although there
isn't that much in the measurements these days.

Even compared to the much praised PCM1704, measurement wise,
the 1853 gives nothing away to the BB chip and betters it in some
areas.

So I have to ask the question, are the old R2R dacs still better?
Or is it really a question of implementation.

Not many people are aware, but the AD1853 has a current set
resistor, (R28 p 14 data sheet) to pin 10 which can be used as a
true analog volume control.

I know of no one who has used this feature but it is
potentially a very good idea, making totally pre amp free signal
chain possible.

Cheers,

Terry
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