Tim Gillett
Banned
Great. Look forward to the photos.
Tim
Tim
Does analog move more air. . . ?
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Victory Pete
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Experiment underway, I am immediately shocked by what I see. I put in a square wave of 1K into my Tascam DA-30 MKII. I get out a square wave with some distortion. I changed frequency to 10K and guess what comes out? A perfect sine wave! If that is not "Fabrication" then what is! This is exciting! Photos coming.
VP
Victory Pete
Banned
Here are the photos of the 1K test
VP
I am having trouble loading photos
VP
I am having trouble loading photos
Victory Pete
Banned
Something is wrong, I still cant post photos. Good old "Digital" strikes again!
VP
VP
Victory Pete
Banned
Lets try again. Nope! If anyone wants photos I can send them to you via e-mail.
VP
VP
mshilarious
Banned
Uh, VP, the first overtone of a square wave is third harmonic, which would be 30kHz for a 10kHz square. So if you set a digital converter to 44.1kHz it will necessarily turn that square into a sine as it removes all content (typically about -100dB) above 22kHz. It's just doing its job as I described in my first post on this thread; it's not exciting, it's bleedingly obvious to anyone who understands the subject matter.
Don't forget to test your tape with the same tones, and also 96kHz digital--which will have the first 30kHz tone, but not the second 50kHz. 192kHz would have 50kHz and 70kHz, maybe some 90kHz.
Also try a listening test: can you hear the difference between a 10kHz sine and square? If so, measure the square's output through your headphones on a spectral analyzer and see if there are any distortions in the audible band. If not, you've just heard 30kHz, which should earn you a Nobel prize.
And yeah, the HR attachment function is broken at the moment . . .
Victory Pete
Banned
My enthusiasm is not affected by your "jibberish". It is simple, what goes into a digital recorder is not what come out. Above 6.5Khz the square wave is "Morphed" into a true sine wave. And what is below is not even close to being a square wave. It seems the digital recorder is "programmed" to always putting out sine waves no matter what goes in.
VP
mshilarious
Banned
Seriously, VP, you are embarassing yourself. *It's all sine waves*! A square wave is an infinite series of odd-order sine waves above a fundamental. Since infinity is impossible in a real-world system, there is no such thing as a true square wave, but even if there was, it would just be an infinite number of sine waves.
6.5kHz * 3 = 19.5kHz, so obviously any square wave much higher than that will only be rendered as its fundamental sine wave at 44.1kHz. I mean duh! Sampling theory 101 here, hello!
Digital is limited by bandwidth, which everybody other than you seems to know, and if you didn't I said it in my first post. 30kHz > 22.05kHz, so a 44.1kHz sample rate won't have any. A 96kHz sample rate will, but you can't hear it anyway.
Try it (you must listen on a reasonable quality 96kHz playback system):
10_30.wav
6.5kHz * 3 = 19.5kHz, so obviously any square wave much higher than that will only be rendered as its fundamental sine wave at 44.1kHz. I mean duh! Sampling theory 101 here, hello!
Digital is limited by bandwidth, which everybody other than you seems to know, and if you didn't I said it in my first post. 30kHz > 22.05kHz, so a 44.1kHz sample rate won't have any. A 96kHz sample rate will, but you can't hear it anyway.
Try it (you must listen on a reasonable quality 96kHz playback system):
10_30.wav
Victory Pete
Banned
mshilarious
Banned
Right, so given that article is pretty much exactly what I am saying (solve the term under "examining the square wave", for example; k=1 is the fundamental, k=2 is the third, k=3 the fifth, and on to infinity), and also given our understanding of digital sampling theory, why were you "immediately shocked" by the result of your experiment? The result should have been your hypothesis.
wikipedia said:
mshilarious
Banned
Here, do something useful: generate a 10kHz sine and compare a tape loop to your DAT loop on a spectral analyzer.
Victory Pete
Banned
Being Digital, the converters did a good job of recreating the 1K square wave, it was still square except you could see the sample points superimposed on it. Analog on the other hand did not show a square wave, as I expected, square sound and magnetic waves can not exist. Of course analog isnt a perfect rendition of the original waveform but at least it is not "fabtricated" by an A/D & D/A converter. My next test will be testing some cymbals, this could be tricky to actually compare input vs. output signals.
VP
Victory Pete
Banned
I am being quite useful today, not only am I doing this test, I have a mixdown project underway.
VP
PS I dont have a "Spectrum Analyzer", yet.
mshilarious
Banned
Do your scopes not do FFT?
What is the FFT (Fast Fourier Transform) math function of an oscilloscope useful for? | Tektronix
What is the FFT (Fast Fourier Transform) math function of an oscilloscope useful for? | Tektronix
mshilarious
Banned
That's correct, cymbals are very difficult to analyze. I tried explaining that several pages ago but you didn't accept the simplified version for test. That test file is still at that link if you want to give it a go.
Victory Pete
Banned
No they dont, they were made in 1992, right at the beginning of the dreaded "Digital Era".
VP
Victory Pete
Banned
I didnt need your explanation of why cymbal signals would be diificult to view on the scope. Funny though, the same thing (cymbals) I think that sounds terrible on Digital also has a very complex waveform, hmm... I wonder why Digital has a hard time reproducing it...........?
VP
mshilarious
Banned
No actually digital should do better with a complex signal because it lacks the magnitude of inharmonic distortion products caused by flutter and probably should have less IMD as well. That is not to say that you might not prefer the distorted cymbals, they might sound more washy as I said many pages ago. But they aren't more accurate. That is what I measured with my fake cymbal test, but you have thus far refused to send that signal (at 96kHz, please) through one of your recorders.
Re: tektronic and FFT, so you would say their modern scopes are defective? Maybe you better call and explain that to them.
If you want a very high quality square wave then as you have learned you need enormous bandwidth above the fundamental. Here is a little Excel chart I did for you with a small realization of the Fourier expansion for a square wave--note that even with 270kHz bandwidth you would have very visible overshoot and ringing on your 10kHz square, and no audio recording system has that much bandwidth (nor is it necessary).
fourier_square.xls
I should say a digital system *could* have 270kHz bandwidth if we were willing to give up some dynamic range--say, down to maybe the 60dB tape provides.
Re: tektronic and FFT, so you would say their modern scopes are defective? Maybe you better call and explain that to them.
If you want a very high quality square wave then as you have learned you need enormous bandwidth above the fundamental. Here is a little Excel chart I did for you with a small realization of the Fourier expansion for a square wave--note that even with 270kHz bandwidth you would have very visible overshoot and ringing on your 10kHz square, and no audio recording system has that much bandwidth (nor is it necessary).
fourier_square.xls
I should say a digital system *could* have 270kHz bandwidth if we were willing to give up some dynamic range--say, down to maybe the 60dB tape provides.
Victory Pete
Banned
Please dont assume anything about what I would say. Both of my 1992 Tektronix 2246 ModA scopes have been 100% reliable, I would however, be a bit "cautious" about buying a new China-made Tektronix Digital scope, you know, things just arent reliable these days. http://www.oregonlive.com/business/index.ssf/2009/08/tektronix_exports_manufacturin.html
VP
Victory Pete
Banned
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