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DSD vs PCM, bit vs hz, Is there a way to compare them fairly?
Arnold B. Kruege...
post Feb 21 2014, 14:42
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QUOTE (AstralStorm @ Feb 20 2014, 17:39) *
So yes, it is averaging a lot (because the FFT is long window - I originally thought a shorter window with major additional averaging specifically because of the sidebands - but that wouldn't reduce the level of the tones either, my mistake). 65k FFT is likely around a second of averaging.


Actually, the length of the averaging period is based on both the sample rate and the length of the FFT. Since this is a 65k FFT and the sample rate is 96 Khz, the period is about 2/3 of a second.

QUOTE
65k FFT should be awfully selective in frequency domain,


Depends what you compare it to. Sample sizes up to 1 million points are available with some FFT-based tools.

QUOTE
therefore the only reason for sidebands is that the generator clocks are just not stable enough.


Completely ignores that there is such a thing as nonlinear distortion in both the amplitude and frequency domains. The later is what we call jitter which can be caused by unstable clocks, but the former is generally far more pervasive and signficiant in the real world.

Generate two or more tones, add nonlinearity in the amplitude domain, mix well, and out pop sidebands.

Nicely summarized here:

http://cp.literature.agilent.com/litweb/pdf/5954-9130.pdf

QUOTE
Therefore any measurement of THD with them will likewise get smeared out and reduced in level...


Not in this world. Real world audio electronics only has enough jitter sufficient to create sidebands that are 80 or more dB below the tone that was modulated by the jitter.

The harmonics in good audio electronics are at least 40 dB down, so the sidebands due to jitter are at least 120 dB down. They might be concealed by the noise floor. Generally speaking distinguishing between two signals that are different by 80 dB is easy enough to do.

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saratoga
post Feb 21 2014, 18:27
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QUOTE (AstralStorm @ Feb 21 2014, 03:23) *
QUOTE (saratoga @ Feb 21 2014, 00:05) *
I would start much more simple than that. A very basic RMAA test on an ordinary PC will give you a good idea if something is wrong with your hardware. No need to use complex equipment yet.


No, it won't. RMAA is quite incomplete in many ways. I'd also need a soundcard with input that is as good or better than DUT.


You just need a sound card that does not have audible IMD. There are literally billions of these in existence.

QUOTE (AstralStorm @ Feb 21 2014, 03:23) *


Do a search, that article is in response to my criticism of nwavguy's instrument fetishism, an odd quirk you seem to be imitating, if not understanding.

Anyway, a simple RMAA test is the first thing you should be doing. One begins with simple, broad tests, and then moves to more specific. Certainly you should have used it before a listening test, let alone anything made by Agilent (which would probably be useless here anyway).
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Arnold B. Kruege...
post Feb 21 2014, 19:09
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QUOTE (AstralStorm @ Feb 21 2014, 03:23) *
QUOTE (saratoga @ Feb 21 2014, 00:05) *
I would start much more simple than that. A very basic RMAA test on an ordinary PC will give you a good idea if something is wrong with your hardware. No need to use complex equipment yet.


No, it won't.



That is one heck of a blanket statement!

QUOTE
RMAA is quite incomplete in many ways.


So is everything short of a Prism, AP or full blown Spectra based measurement system. However, the task at hand is not the grand inquisition or a name-dropping contest.

QUOTE
I'd also need a soundcard with input that is as good or better than DUT.


Who can say this after chastising me for using a too-good sound card that was something with a whopping 8 analog channels in, 8 analog channels out, symmetrical I/O performace and $100 on eBay?

QUOTE
I'm not sure I can trust the Lynx for this yet, since I haven't measured its input.


If you are talking about the LynxTWO, its most noteworthy oddity is that its nonlinear distortion is impressively minimized at FS -10 dB or so but near FS, its just another ca. 100 dB audio interface.

QUOTE
(I can make RMAA handle absolute levels by calibrating the level beforehand with the voltmeter.)


One can make RMAA very omnivorous with respect to levels by doing the recording of the test tones with something other than RMAA.
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AstralStorm
post Feb 22 2014, 16:57
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I don't have a soundcard that is separate from the DUT. Not Lynx Two, but Lynx Hilo.
I could assume it has a great input, which it likely does, but then, I cannot be sure until I measure it, non-loopback.
I'm wary since FP10 has a broken input. (in terms of FR) (Which happened to be found via an extremely cheap old scope.)

$100 for M-Audio Delta 1010LT on ebay? Wow. That thing used to cost $1000+. What a deal. Now, a new one costs $300.

Exactly what I will do, is to take the recordings of the tests and check them with a separate tool indeed.

--
Regardinig the sidebands, I'd expect something looking closer to: https://www.macomtech.com/static/PDFs/Techn...cterization.pdf
With clear separation between test tones. And those graphs are for RF, not audio, where it's harder to have a stable signal source.
The sidebands here are way excessive. (Blackmann window has slow rolloff, but at 65k FFT that shouldn't matter much.)
All of ARTA, RMAA, TrueRTA and REW do not feature such huge sidebands in THD or IMD measurements. The source peaks should be tight and clear.

I need an actual explanation for them unless I fully accept the measurement. Saying "oh, it's some kind of distorion but not IMD" does not cut it. It's either misset FFT (unlikely given the information) or something else broken, likely the signal generator.

This post has been edited by AstralStorm: Feb 22 2014, 16:59


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Arnold B. Kruege...
post Feb 23 2014, 17:44
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QUOTE (AstralStorm @ Feb 22 2014, 10:57) *
$100 for M-Audio Delta 1010LT on ebay? Wow. That thing used to cost $1000+. What a deal. Now, a new one costs $300.


Not really. The 1010LT is the one with a RC socket RS-232 dongle instead of a outboard 1RU interface. Street price was never higher than $200

The one with the outboard rack-mounted box was the Delta 1010 (no LT). It was a few dB better and had wall-to-wall TRS balanced I/O. Never sold for more than $500 and I have one of those, too.

[quote]
Regardinig the sidebands, I'd expect something looking closer to: https://www.macomtech.com/static/PDFs/Techn...cterization.pdf
With clear separation between test tones. And those graphs are for RF, not audio, where it's harder to have a stable signal source.
The sidebands here are way excessive. (Blackmann window has slow rolloff, but at 65k FFT that shouldn't matter much.)
All of ARTA, RMAA, TrueRTA and REW do not feature such huge sidebands in THD or IMD measurements. The source peaks should be tight and clear.[quote]

You are in a self-made quandry. You demanded multitones, and you got multones. Of course tests with just 2 tones rather than about 30 give clearer indications. You should be careful about what you ask for - you may get them!

The public faulting of my tests has made me very unwilling to bow and scrape as you seem to be demanding, Take what you got - you've exposed your level of knowledge in this topic and I'm done with you!

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splice
post Feb 23 2014, 20:39
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QUOTE (includemeout @ Jan 17 2014, 12:38) *
OT I know, but It seems to me it's not only format names which are unicorn-like, as I can't help thinking the Schiit folks were really having a laugh/taking the wee at all audiophools when they came up with that horrid name o' theirs - even if it (probably) is their family name.


History of Schiit Audio by the co-founder:
http://www.head-fi.org/t/701900/schiit-hap...obable-start-up

How the name came about:
http://www.head-fi.org/t/701900/schiit-hap...5#post_10286931

This post has been edited by splice: Feb 23 2014, 20:42


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AstralStorm
post Feb 24 2014, 09:10
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QUOTE (Arnold B. Krueger @ Feb 23 2014, 17:44) *
You are in a self-made quandry. You demanded multitones, and you got multones. Of course tests with just 2 tones rather than about 30 give clearer indications. You should be careful about what you ask for - you may get them!


I didn't ask for 20 tones and for the sidebands. smile.gif I've personally ran a 7 tone test with no such issues and a "cheap" digital scope to boot. No idea why you have these. Pity that scope can only do about -100 dB before the noise floor hits. Anyway, next time (a long time) I'll be back with some measurements.

--
Also, I do love Schiit story. They do make excellent and cheap amplifiers. (Though not the very best, but close, top 10.) Apparently our measurements have blind spots too - we need to figure out better ones and again, correlate with listening tests.

This post has been edited by AstralStorm: Feb 24 2014, 09:27


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ruxvilti'a
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Arnold B. Kruege...
post Feb 27 2014, 14:03
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QUOTE (AstralStorm @ Feb 24 2014, 03:10) *
QUOTE (Arnold B. Krueger @ Feb 23 2014, 17:44) *
You are in a self-made quandry. You demanded multitones, and you got multones. Of course tests with just 2 tones rather than about 30 give clearer indications. You should be careful about what you ask for - you may get them!


I didn't ask for 20 tones and for the sidebands. smile.gif I've personally ran a 7 tone test with no such issues and a "cheap" digital scope to boot.


From an audio perspective cheap digital scopes are useless. They are typically based on 8 bit conversion which is good enough for the purpose of looking at waveforms, but not so much for quality audio. The better ones go up to 12 bits, but analytical software at its best can only follow the example of the human ear, and we already know that 12 bits is marginal to inadequate for high quality listening.


QUOTE
No idea why you have these. Pity that scope can only do about -100 dB before the noise floor hits.


As I demonstrated discrete signals well below -100 dB are clearly visible with that hardware.

QUOTE
Anyway, next time (a long time) I'll be back with some measurements.


Pardon me while I continue breathing steadily and calmly! ;-)

I seem to recall something about claims of artifacts that were 40 dB down. One thing that even an illusory -100 dB noise floor is that it would show them clearly if they existed.
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