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Old 3rd April 2012, 01:40 AM   #11
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Well, I saw that, but trully... the filters in the DAC should take care of those ultrasonics. And if they don't, why should the software ignore them? It is still distortion that get applied to the following chain. Anyway, in my second batch of measurements the limit was at 20kHz. Source was 16 bit not dithered. Observe that I didn't use the A-weighting that you did use.

I am not sure how it calculates the THD and THD+N, but the numbers for the 16 bit signal seem right to me.

Last edited by SoNic_real_one; 3rd April 2012 at 01:47 AM.
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Old 3rd April 2012, 04:22 PM   #12
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Yes but no..... For example, I have a NOS TDA1541a source. I am frankly not very interested in the obvious artifacts at the top end...

I have made the choice to go NOS consciously, knowing that these artifacts exist. Now, during my measurements, I don't want to be bothered with them anymore....

Screen shot 2012-04-03 at 6.20.08 PM.png
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Old 3rd April 2012, 10:40 PM   #13
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Ignoring a problem does not make it go away.
Play two frequencies - one 19kHz and one 20kHz at 1:1 and see what happens.

Last edited by SoNic_real_one; 3rd April 2012 at 10:46 PM.
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Old 3rd April 2012, 11:15 PM   #14
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This are my results for 19kHz and 20kHz (1:1) for PCM61 @ 8x (first pic), TDA1541 @ 4x (second pic) and PCM1791 @ 16x (third pic) - set Arta output at -1dB. Once again - 16 bit, 44.1kHz.
The beats between the two (separated at 1kHz) are normal. I am really curious to see the NOS.
Attached Images
File Type: png PCM61_19_20_1dB.PNG (71.0 KB, 132 views)
File Type: png TDA1541_19_20_1db.PNG (64.9 KB, 127 views)
File Type: png PCM1791_19_20_1db.PNG (70.8 KB, 130 views)

Last edited by SoNic_real_one; 3rd April 2012 at 11:29 PM.
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Old 4th April 2012, 03:15 AM   #15
Previously: Kuei Yang Wang
 
Join Date: Nov 2002
Hi,

Quote:
Originally Posted by SoNic_real_one View Post
Ignoring a problem does not make it go away.
And precisely what problem are you referring to?

Ciao T
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Old 4th April 2012, 03:20 AM   #16
Previously: Kuei Yang Wang
 
Join Date: Nov 2002
Hi,

Quote:
Originally Posted by studiostevus View Post
Yes but no..... For example, I have a NOS TDA1541a source. I am frankly not very interested in the obvious artifacts at the top end...
You should be.

Quote:
Originally Posted by studiostevus View Post
I have made the choice to go NOS consciously, knowing that these artifacts exist. Now, during my measurements, I don't want to be bothered with them anymore....

Attachment 275200
A suggestion. Play wideband noise, filtered with a 1st order LPF at 1KHz. Do a FFT at 192KHz sample rate.

Observe the resulting spectrum. Then compare with the Spectrums of real instruments provided in James Boyk's paper. The look again at your spectrum and then squint a little to make it blurr a trifle.

If you do it right you may experience what I call a BFO...

Ciao T

Last edited by ThorstenL; 4th April 2012 at 03:28 AM.
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Old 4th April 2012, 03:27 AM   #17
Previously: Kuei Yang Wang
 
Join Date: Nov 2002
Hi,

Quote:
Originally Posted by SoNic_real_one View Post
This are my results for 19kHz and 20kHz (1:1) for PCM61 @ 8x (first pic), TDA1541 @ 4x (second pic) and PCM1791 @ 16x (third pic) - set Arta output at -1dB. Once again - 16 bit, 44.1kHz.
It shows (unsurprisingly) the PCM1791 as best, but the cute part is that the TDA1541 beats the pants off the notionally 18 Bit PCM61 and IIRC your PCM61 has another two bits added discrete, right?

Ciao T
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Old 4th April 2012, 05:59 PM   #18
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This is 19+20Khz 1:1 on my NOS TDA1541a.... to be honest, I don't really know what I am (supposed to be) looking at.... enlighted me..

Screen shot 2012-04-04 at 7.58.10 PM.png
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Old 4th April 2012, 06:10 PM   #19
Previously: Kuei Yang Wang
 
Join Date: Nov 2002
Hi,

Quote:
Originally Posted by studiostevus View Post
This is 19+20Khz 1:1 on my NOS TDA1541a.... to be honest, I don't really know what I am (supposed to be) looking at.... enlighted me..

Attachment 275408
Do as I said, this is a whole other kettle of fish:

"Play wideband noise, filtered with a 1st order LPF at 1KHz."

You are playing two sinewaves and you are sampling at 96KHz.

Though you may draw inferences of what you will see from this, or indeed basic theory.

Ciao T

Last edited by ThorstenL; 4th April 2012 at 06:13 PM.
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Old 4th April 2012, 07:53 PM   #20
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LPF... How? Where? In Arta?
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