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Extreme pure sine (0.0007% THD+N) Metering & Analysis Plugins
Old 9th June 2016
  #1
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Extreme pure sine (0.0007% THD+N)

Extreme pure sine (0.0007% THD+N) with level of 775 mVrms
15 Hz - 400 Hz - 1000 Hz - 3000 Hz - 6000 Hz - 12000 Hz - 18000 Hz

Sine Ultrapure

Old 9th June 2016
  #2
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O.K. and..?

Most of DAWs, tone generator tools or plugins can generate sine waves with arbitrary dBFS level and frequency.
Plus listed Vrms rating with 1% tolerance also doesn't make any sense, because actual voltage level always depends on particular playback settings and device, where you are going to play such waveforms.

Michal
Old 9th June 2016
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I use it to see how much noise is added to the bottom from the D.U.T. and
many of the generator tools do not have a 'like' low reference noise level.
Your generator have this very low low low noise signal ?
Obviously the gain of the player must be put at the highest level ie 0 dbfs.
We do not care the volume but the bottom noise

Old 10th June 2016
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Old 10th June 2016
  #5
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One of the waveform file displayed with a suitable program to do these things, it is Wavosaur, you can see well the very low noise floor...
Old 10th June 2016
  #6
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With regards to the description of files..
VRms or level is just non-sense with regards to measurement in digital domain or digital test files, because it depends on particular D/A converter, one device has its 0dBFS mapped to +22dBu and another one to +16dBu, third one to 2VRms.. so output voltage with the same digital file will be different. Power in mVRms??
Only meaningful rating there is in dBFS.. eg. sine -3dBFS, 997Hz
Similarly SNR.. what's that figure in the context? It certainly makes sense to publish SNR for some device like D/A converter or preamp, but not for test file. And still SNR has to be related to some fixed value (eg. +4dBu in case of analog output or let's say 0dBFS in case of some digital processor, plugin etc.) and also SNR is directly related to measured bandwidth (assuming there isn't any filter used, so it is whole audioband at 48k rate - 24kHz).

Besides that.. exact THD+N figures obtained by digital FFT spectrum analyzers are also related to used windowing algorithm (eg. Kaiser, Hanning, Blackman function).. and implementations of analysis in particular program, especially if we're talking about those very low values.

Anyway, one should also look at practical use of such measurements, if we'll be talking about measurement of typical analog devices, then it really doesn't matter if noisefloor in some test file appears to be at -150 or -170dBFS at your FFT analysis software, because noisefloor of converter or device itself will be higher and mask all of that. Not to mention a chance to hear some artifacts with human hearing
Of course, dedicated measurement programs like ARTA or SpectraPlus from your screenshots have high quality oscillators built-in.

When measuring some software (eg. DSP algorithm "in the box" like plugin or so), then you can use some native measurement without necessary conversions.. for example floating point wave file or signal generator and some FFT plugin like Voxengo Span, which will accept floating point input. Or dedicated software like VST plugin analyzer.

With your concerns about purity of sine generators, which are certainly much easier to do than square waves or saws, where one should care about band-limiting.. I've personally never experienced problems with that for example when I used built-in generators in Samplitude or Reaper..
If someone doesn't have such programs, then its easily possible to use some open source tools for high quality sines..
like command-line SoX
Code:
sox -c 1 -r 48000 -n -b 24 sine-997hz-3dbfs.wav synth 10 sin 997 gain -3 dither
(this will generate file with 1 channel at 48k, 10s, sine wave at 997Hz with -3dBFS level and dither that to 24bit for output)

or Audacity with its tone generator, which can do also perfect square waves to 32bit floating point files.

You can check FFT plot of 24bit dithered file generated by SoX (yellow) or 32bit float file generated by Audacity and played from Reaper to the analyzer.. it's as good as it can possibly be..

Michal
Attached Thumbnails
Extreme pure sine (0.0007% THD+N)-pure-sine.png  

Last edited by msmucr; 10th June 2016 at 10:50 AM..
Old 10th June 2016
  #7
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The first thing, I have never talked about dBfs, never
because it depends on D/A converter welded by the manufacturer to the soundcard and each full scale are different.

I answer in sequence to your writings

non-sense for digital-domain and this your statement is little tight but fair...but the original total power of sinewave is in dBV like dBu like dBrG like mW and don't like RMS, sorry, on this you're right, I was wrong, tiredness sometimes wins over reason.
'total amplitude of sinewave' is right ?
I just corrected the error, thank you.

i dont know the -3 dBfs 997 Hz, the output of my signal generator have Vpp ,Vrms and Vp and 0 to 25 Mhz
I think that the A-weighted and other things in this case nothing to do.

SNR is related on the orginal signal generator output and it is in this context,
other things eg bandwith are not important in this case AND
the THD+N is related also to the original ouput generator

Anyway

with human hearing we do really not much, I think we can much more with the 'overaly' comparision function

Arta or Spectraplus have high quality oscillators built-in, yes, and for well recording this signal you need a hardware recorder, better still if the recorder is even physically plug inside the DAC chip, like Lynx or RME.

thanks for the news of SOX, if you do not have a high-quality digital generator is certainly a good alternative

This is not a soundcard DAC

Last edited by CD_Audio; 11th June 2016 at 07:36 AM..
Old 11th June 2016
  #8
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Quote:
Originally Posted by msmucr View Post
You can check FFT plot of 24bit dithered file generated by SoX (yellow) or 32bit float file generated by Audacity and played from Reaper to the analyzer.. it's as good as it can possibly be..

Michal
With regards to the Arta screenshoot
This is my 'The imperfect sine' (tm) in ARTA
Old 11th June 2016
  #9
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Added wav file with a kind of frequency response made with a 20 tones and almost 4 dbu to the origin output.





http://www.bonisaudio.com/baf/ultrapure.html
Old 12th June 2016
  #10
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Quote:
Originally Posted by msmucr View Post
like command-line SoX
Code:
sox -c 1 -r 48000 -n -b 24 sine-997hz-3dbfs.wav synth 10 sin 997 gain -3 dither
(this will generate file with 1 channel at 48k, 10s, sine wave at 997Hz with -3dBFS level and dither that to 24bit for output)

Michal
i have tried SoX ,
there are only small differences with my waveforms, good.
Old 13th June 2016
  #11
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QUASI PURE SINE
Added Lissajous waveform file (zip/wav) to the download page.
Old 21st June 2016
  #12
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News...
QUASI PURE SINE
Old 28th June 2016
  #13
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Don't Get Lost in the Noise Floor PDF
http://www.analog.com/media/en/train...als/MT-003.pdf
Old 28th June 2016
  #14
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I have written a custom macro to explore the noise floor at various frequencies,
This macro creates a auto-text txt file which contains all the results.


this other noise floor video is 20 KHz - 90 KHz range (HD?)


Last edited by CD_Audio; 29th June 2016 at 11:21 AM..
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