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Author Topic: Standard Distortion Spectrum Measurements For Amps (Changstar)  (Read 2153 times)

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OJneg

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Re: Standard Distortion Spectrum Measurements For Amps (Changstar)
« Reply #10 on: July 30, 2015, 01:15:19 AM »
Well it matters if we're talking about getting comparable measurements, especially for LF distortion tests.
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OJneg

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Re: Standard Distortion Spectrum Measurements For Amps (Changstar)
« Reply #11 on: July 30, 2015, 01:26:00 AM »
Examples:









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Marvey

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Re: Standard Distortion Spectrum Measurements For Amps (Changstar)
« Reply #12 on: July 30, 2015, 01:41:09 AM »
You are making this much more complex than it needs to be. Simply use the skinniest longest [redickted] shape. I don't know why ARTA Hanning sucks.

See here for examples from QA400: http://www.changstar.com/index.php/topic,2617.0.html
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OJneg

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Re: Standard Distortion Spectrum Measurements For Amps (Changstar)
« Reply #13 on: July 30, 2015, 01:56:33 AM »
Quote from: marvey on July 30, 2015, 01:41:09 AM
You are making this much more complex than it needs to be. Simply use the skinniest longest [redickted] shape. I don't know why ARTA Hanning sucks.

See here for examples from QA400: http://www.changstar.com/index.php/topic,2617.0.html

Ok, so let's say people should stick to Kaiser5 with 131072 FFT if they're going to use ARTA for measurements. Just want to clear things up so people don't post random shit and ask what's wrong.
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Marvey

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Re: Standard Distortion Spectrum Measurements For Amps (Changstar)
« Reply #14 on: July 30, 2015, 02:03:01 AM »
Exp. averaging? The window size seems rather large... might barf on older laptops and PCs.
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OJneg

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Re: Standard Distortion Spectrum Measurements For Amps (Changstar)
« Reply #15 on: July 30, 2015, 02:17:23 AM »
We're talking about FR now? Need different settings. I propose periodic white noise (PN white), 32768 FFT and Uniform window, linear averaging

Increase FFT size to capture more subsonics, increase sample rate to get more ultrasonics, with obvious trade off between the two
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Marvey

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Re: Standard Distortion Spectrum Measurements For Amps (Changstar)
« Reply #16 on: July 30, 2015, 04:42:46 PM »
Quote from: OJneg on July 30, 2015, 02:17:23 AM
We're talking about FR now? Need different settings. I propose periodic white noise (PN white), 32768 FFT and Uniform window, linear averaging

Increase FFT size to capture more subsonics, increase sample rate to get more ultrasonics, with obvious trade off between the two

Essentially the standard will be "don't be a retard on FFT Windows". We are not writing ISO or ANSI. It's going to be obvious on the plots when someone is retard.
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OJneg

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Re: Standard Distortion Spectrum Measurements For Amps (Changstar)
« Reply #17 on: July 30, 2015, 06:28:02 PM »
Ok, fine by me.

I think we should expand the tests to include wide-band FR. If there are any strange subsonic (weird DC servo activity, too small coupling cap) or ultrasonic (oscillation caused by limited open-loop gain, peaking caused by signal transformer) then that should be revealed. I don't think I am alone in thinking that out-of-band activity can have an effect on sound quality.
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Marvey

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Re: Standard Distortion Spectrum Measurements For Amps (Changstar)
« Reply #18 on: July 30, 2015, 06:30:28 PM »
Agreed. Wide-band FR as far out as possible (limited by sampling rate of ADC and signal generators)

at spec'd power and loads.

Going to try Donald's recommended .550Vrms and see if its a good start.
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OJneg

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Re: Standard Distortion Spectrum Measurements For Amps (Changstar)
« Reply #19 on: July 30, 2015, 10:11:15 PM »
Thoughts on including square wave tests?
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