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Old 28th March 2004, 11:58 AM   #1
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Arrow Need -60dB 1kHz sine wave for CD

Hi,

I need a 1 minute 1kHz -60dB uncompressed sine wave track, which I can burn on a cd rom and play in a CD player.

It is for DAC linearity testing.

Is there a free program for that on the net ?

Or does anybody have that and can email it to me ?

Thanks,

Bernhard
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Old 28th March 2004, 12:42 PM   #2
Netlist is offline Netlist  Belgium
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Old 28th March 2004, 01:10 PM   #3
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www.goldwave.com ... easy as that...

keep us posted on yourt results!

cya,
Thijs
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Old 28th March 2004, 07:02 PM   #4
Pedja is offline Pedja  Serbia
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Bernhard,

Please note that if you just synthesize 1kHz -60dBFS 16 bit file, it will have the embedded distortion of about 0.75%. If you plan to measure the TDA1541, this distortion is close to the chipís specs. Naturally, for the distortion measurement of the chips with better distortion figures and nowadays there are a plenty of them, such file is useless.

Another file can serve much better for this purpose. It is synthesized originally like 32 bit file and is converted down to 16 bit using dither and noise shaping. The result will depend on the FFT parameters used for the analysis, with Hanning windowing and 65536pts something like 0.012% is achieved. Below are the graphs showing the difference between these two files.


Click the image to open in full size.


The files are here:
http://uk.geocities.com/react_71/

Pedja
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Old 28th March 2004, 09:04 PM   #5
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Hi Pedja,

Hmmmmm that's interesting.... could you eleborate on the distortion level of the 'normal' -60dB signal and the method you usefd to create the improved file you made? I would be most interested!!


Regards,
Thijs Schrama
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Old 28th March 2004, 09:06 PM   #6
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And how did you measure the THD figure, how did you made those nice graphs?? They seem confinsing... but what DAC can be sooo linear?


greetz.
Thijs
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Old 28th March 2004, 09:59 PM   #7
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Pedja,

thanks, I will burn the CD tomorrow and maybe this helps.

Just found another test CD with better 1 kHz 0dB sine than the other one.

1541 and silvercrown are totally identical ( +/- 0,0dB ) except K3:

1541 is -69,8dB
Silvercrown is -70,2dB

Repetitive accuracy of the analyzer is 0dB.

No idea what is the embedded distortion of the sine from this CD.
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File Type: jpg tdadistnew.jpg (72.3 KB, 338 views)
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Old 29th March 2004, 12:41 PM   #8
Pedja is offline Pedja  Serbia
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Thijs, as the opposite of the phenomenon usually found in the analog devices, in the digital the distortion increases as the signal level decreases. The numbers mentioned above are the limits of the format we are operating with.

The dither is the technique that can improve the distortion at low level at the expense of the higher noise floor. Noise shaping isÖ the name is self descriptive.

For the file I uploaded it was used the high-pass triangular dithering. In this graph the red line shows the same dithered signal but the noise shaping was not used.


Click the image to open in full size.


The graphs are analysis of the files themselves, so no D/A conversion was involved in this.

There is interesting presentation that can be found here:
http://www.angelfire.com/music4/audio_visions/know.html
(check Dither and noise shaping demo by Chris Hicks)

Bernhard, if there was not any huge mistake while the file was generated, its embedded distortion should be negligible in the results you achieved. However, the numbers should be lower and there is probably some other source of distortion that dominates there. Considering the difference between S1 and non-S1 versions of TDA151A, according to Philips, it is in the linearity at the low level.

Pedja
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Old 29th March 2004, 12:57 PM   #9
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Thanks Pedja! Excelent link too... too bad the demo matlab file doesn't work

cya,
Thijs
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Old 29th March 2004, 05:07 PM   #10
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Quote:
Originally posted by Pedja
Bernhard, if there was not any huge mistake while the file was generated, its embedded distortion should be negligible in the results you achieved. However, the numbers should be lower and there is probably some other source of distortion that dominates there. Considering the difference between S1 and non-S1 versions of TDA151A, according to Philips, it is in the linearity at the low level.

Pedja
Pedja,

this picture was from another test CD with -0,5dB.

I will try your signal and that from Hugo now.

Bernhard
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