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Old 31st March 2011, 12:12 PM   #1
Elvee is offline Elvee  Belgium
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Default Remember: you don't hear with your eyes....

Hi,

This thread has drifted off-topic, but in a direction worth investigating further.

Let us begin with a small quiz.

a)Which of the following waveform has, in your opinion, the highest distortion level: is it 1 (magenta) or 2 (green).

b)More controversial: which of the waveform has the most offensive distortion contents?

Think carefully before giving your answers.

In due time, I will reveal how the signals were created.
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File Type: gif THDcompar2.GIF (17.6 KB, 394 views)
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Old 31st March 2011, 01:19 PM   #2
AKSA is offline AKSA  Australia
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Magenta = highest distortion
Green = most offensive (high, odd order)
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Old 31st March 2011, 05:19 PM   #3
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Never had a meter, don't have an informed opinion. The high frequencies in the green would stand out to the ear because there isn't any high freq in the fundamental to cover it up. Psychoacoustics. The magenta wiggle, I don't know what it would sound like but it is low freq distortion. Its more of a reed stop than a flute stop. Doesn't have the right angle turn of the green.
I can spot clipping, hum, and high freq switch noise distortions with my eyes, and minimize.
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Old 31st March 2011, 05:30 PM   #4
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Quote:
Originally Posted by AKSA View Post
Magenta = highest distortion
Green = most offensive (high, odd order)
Total agreement , and neither are clipping as well. You can get either one by building an amp wrong.

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Old 31st March 2011, 05:33 PM   #5
Elvee is offline Elvee  Belgium
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Quote:
Originally Posted by indianajo View Post
I can spot clipping, hum, and high freq switch noise distortions with my eyes,
Are you that sure?

Obviously, if I launched this discussion, it is because the matters are highly counter-intuitive.

And if chose this title, there has to be a good reason.

Any afterthoughts?
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Old 31st March 2011, 05:44 PM   #6
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I just got the magenta waveform , I used a non- beta enhanced blameless (loaded the IPS down - below) I could not get the green one no matter what i did (even hard clipping into 2 R loads).

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Old 31st March 2011, 08:12 PM   #7
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Quote:
Originally Posted by Elvee View Post
Are you that sure?

Obviously, if I launched this discussion, it is because the matters are highly counter-intuitive.

And if chose this title, there has to be a good reason.

Any afterthoughts?
If the fundamental wave was at a multiple or sub-multiple of the power line frequency, I would miss hum. At non-integer frequencies, hum makes the tips bounce up and down at the power line freq. Standard piano frequencies are 58.3 Hz and 61.7 so if the source is music this shouldn't be a problem.
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Old 31st March 2011, 08:59 PM   #8
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Hmmm... I'm going to give the opposite answer than AKSA. The green has higher distortion, but it sounds better to us humans.
Kinda guessing, but not without some reasoning...
And hopefully one of us is correct.
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Old 31st March 2011, 09:15 PM   #9
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This looks like 1000 hz which is not divisible by 60 but is divisible by 50. You're in Germany where the power is 50 hz. Use a Hammond organ to generate your sine wave signal and you won't have this even multiple problem. Freq would be 987 or 1046 Hz.
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Last edited by indianajo; 31st March 2011 at 09:18 PM.
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Old 31st March 2011, 09:16 PM   #10
DF96 is offline DF96  England
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a - don't know (possibly magenta, as it could have lots of low order distortion but I am not sure)
b - green (more high order distortion because of a sharp transition)

Both waveforms look symmetric, so distortion will be odd-order. The green one is just crossover distortion - zero gain around the zero crossing. The magenta one could just be something like half of green plus half of undistorted sine wave. In either case it looks like just a few percent distortion.
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