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DiAna, a software Distortion Analyzer
DiAna, a software Distortion Analyzer
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Old Yesterday, 03:57 PM   #871
Frex is offline Frex  France
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Hello,

Those oscillating symmetric square waves are typical from Delta-sigma ADC
and come from the digital FIR filtering inside ADC/DAC.
(SAR ADC's can produce much more flat square wave).

I'm very curious then to try my ADC with Diana...


Frex
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Old Yesterday, 04:10 PM   #872
Edmond Stuart is offline Edmond Stuart  Netherlands
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Default SAR-ADC

Quote:
Originally Posted by Frex View Post
Hello,
Those oscillating symmetric square waves are typical from Delta-sigma ADC
and come from the digital FIR filtering inside ADC/DAC.
(SAR ADC's can produce much more flat square wave).
Yes.
Quote:
I'm very curious then to try my ADC with Diana...
Frex
Me too! But currently, DiAna supports only the ASIO protocol. So there might be a compatibility issue.

Cheers, E.
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Old Yesterday, 05:11 PM   #873
phofman is offline phofman  Czech Republic
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Quote:
Originally Posted by Frex View Post
Hello,

Those oscillating symmetric square waves are typical from Delta-sigma ADC
and come from the digital FIR filtering inside ADC/DAC.
(SAR ADC's can produce much more flat square wave).
The higher the sample rate, the smaller the overshoots, i.e. the closer the sampled signal is to the analog true square wave. The higher harmonics contribute to the "sharp corner" of the square wave.

Have you compared your SAR ADC with a delta-sigma DAC outputting the same samplerate? IMO if both are correct they should produce the same output, otherwise one of them is lying (introducing distortion, i.e. not correct).
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Old Yesterday, 05:48 PM   #874
Frex is offline Frex  France
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Phofman,
I already posted a time domain response of my SAR ADC analyzer here.
The response doesn't have the symmetric ripple because there is no FIR filter
(only a SinC one that is a RII filter type).
If i add a FIR filter to remove aliasing frequency above, the result is same as
conventional delta/sigma ADC. The OSVA will differ in way were you can choose
of what filter you want to use (depending on your own need).
But the ripple at output of the FIR is the consequence of the very sharp rolloff
of the filter that remove all frequency above it's cutoff.
(Square wave require infinite number of harmonics to become really square).

Edmond,
No worry, i actually use the SPDIF output of the AA2380v1 board and send
the stream to a RME HDSP9632 that have ASIO drivers.
When OSVA will use the USB-streamer board or even the SDR-widget,
ASIO is supported too.


Frex
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Old Yesterday, 06:14 PM   #875
1audio is offline 1audio  United States
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DiAna, a software Distortion Analyzer
This is getting a little weird.

1) Testing an audio link through microphones and speakers looking for waveform fidelity will be really disappointing. There are many valid fundamental reasons why that won't be easy. Starting with a real world room and going on to the impact of a directional microphone. Not an easy issue to resolve.

2) Band limited square waves. Been an audio red herring for years. If you use an analog or a wide band digital scope you can see the leading edge of a real square wave. That square wave won't exist in a band limited audio chain. But audio channels are all band limited starting with the microphone, then the recording medium then the reproducing system and finally human hearing. In the analog days the brick wall was at more like 15-18 KHz and had to do with the nature of a recording head and bias oscillators. Digital had the promise of 'perfect fidelity" but only within the legitimate band and the closer you pushed to the Nyquist limit the more artifacts you have. However a real world audio link with a microphone won't have much content above 12 KHz at level and very little above 20K under the best circumstances. The distorted output from the "premium" dac was an effort for a better subjective experience as the expense of objective fidelity. Look for a measurement of amplitude and phase vs frequency to get a better idea of how faithful the channels is to the input. Acoustic square waves only exist in conditions that are dangerous to human health (and they are not square because air is not perfectly linear).

You could try recording a balloon popping with both a 1/4" measurement microphone and a normal recording chain and see how degraded the impulse is on a playback chain. However that's only really relevant to those who listen to balloons popping for entertainment. Doing the same with spoken word will tell a lot about real intelligibility of the chain which I posit is far more important.
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Old Yesterday, 09:39 PM   #876
voltwide is offline voltwide  Ireland
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Is there anybody who managed Diana working under Linux/Wine?
Or is this definitely impossible?
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Old Yesterday, 11:37 PM   #877
6vheater is offline 6vheater
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Quote:
Originally Posted by voltwide View Post
Is there anybody who managed Diana working under Linux/Wine?
Or is this definitely impossible?
If I understand it right ASIO is the problem.
Try as you might, you can't get that to interface any of that to Linux audio (a can of worms if there ever was one!)

Other question:-
Quote:
Originally Posted by 1audio View Post
1) Testing an audio link through microphones and speakers looking for waveform fidelity will be really disappointing.
There are many valid fundamental reasons why that won't be easy.
Starting with a real world room and going on to the impact of a directional microphone. Not an easy issue to resolve.*

However a real world audio link with a microphone won't have much content above 12 KHz at level and very little above 20K under the best circumstances.**
NO WAY.
A simple FFT analysis is very revealing comparing 2 microphones at exactly the same locations*.
Once you start inspecting waveforms and see disparities between the 2 microphones in distortion signature,you are barking up the right tree.

**You are joking?
One of the principal requests I had from the microphone manufacturer, was, can I do testing in the ultrasonic area?
Watching the HF response of my own system, I can see (and hear) clearly 15khz, so when we go off above that, the mic is clearly generating signal.

I asked my young daughter to do a hearing test (this time with headphones).
Ran a 23khz sine through it, she jumped, held her ears and ran off, refusing to do anything like it again!

Last edited by 6vheater; Yesterday at 11:49 PM.
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