DiAna, a software Distortion Analyzer

Now that all the RTX 6001 have been shipped (and delivered?) it seems to me the right moment to "go public" with a free demo version of DiAna. For those who never heard of DiAna, it's a software tool (in conjunction with a ASIO sound card) to measure distortion (THD+N and THD-N). The pro version also measures IMD and the frequency response. Furthermore, the demo version is a bit crippled in that recording of the signal and data processing has been slow downed (i.e. separated into two steps). As an example, please, see below the loop back results of a Lynx L22 sound card.
As for the lower part of the pictures:
1st. graph: Spectrum of the harmonics only.
2nd graph: Full spectrum with coherent integration (averaging).
3rd graph: Full spectrum with incoherent integration.
As for the upper part all pictures: green is input signal, yellow is residual.
(the height of upper and lower part can be varied at will, of course)
For more details, please send a PM.
Cheers, E.


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How does this determine the residual? Regression from a fit of the input to the output signal (fitting amplitude and time lag)?
The residual is obtained by subtracting a pure sine from the (coherent integrated) input signal. In order to remove HF rubbish, you can low-pass filter the residual. This is done by means of an FFT and inverse FFT (BTW, actually, I'm using FHT's)
Also, will DiAna work on non-Windoze systems (Linux, Macs)?
Nope, only under 'windoze'. Regarding other systems you might try to run it on an emulator. Probably it works, as DiAna only makes use of standard Win32 calls (no MFC rubbish).
One more important thing: DiAna is not just a spectrum analyzer, instead, it's a distortion analyzer.
Cheers, E.


2012-08-11 8:14 am
I got the same error message with both links, and there is no https:// added.

The domain data-odyssey.nl is resolvable from online DNS portals, so it's probably something to do with my ISP. Given some behavior I've seen, it seems like my ISP is purposely hiding/blocking this site.
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Indeed, a good question. To do it right and accurately, it is far from easy. As for the fundamental, hundreds lines of code were needed to extract the frequency, phase, amplitude and offset from the data. How exactly I've done it, I won't tell you, sorry. But it is done as accurate as possible with an error rate in the order of 1E-6 to 1E-22, depending on the background noise, of course (as you know: 'garbage in, garbage out', which also applies in this case, alas).
Microsoft Security Essentials says the zip contains a virus and automatically deletes the file. This is a first for me. Safe or no?
It is a false positive as only two out of 60 virus scanners are wining about "not-a-virus:AdWare.Win32.Gamevance.gen", see list below (generated by virustotal.com). Anyhow, a virus or not, it's harmless.
Cheers, E.


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