John Curl's Blowtorch preamplifier part III

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You know very well I was speaking in that context about practicalities of numerical approximations used in measurement, what they show and don't show.

Nope, you were talking about why and when music cannot be considered a sum of sines:

However, as a practical matter there are some things it won't show well. There was a patent IIRC to randomize the crossover voltage of a class AB or class B output stage. That makes the crossover distortion appear at a random point in each waveform. If we take a long FFT to get good frequency resolution, that crossover distortion will seem to have disappeared which might make someone miss it or believe it to be inaudible, which it is likely not. If we use a short FFT of one cycle of a test sine wave, then the crossover distortion will not be random for that one cycle, but then noise will also appear to be more deterministic.

Sorry, it's still hogwash.
 
Sorry, <syn08 is> still hogwash.

Your lie of omission by leaving out my immediately preceding sentences to the part you quoted is a well known plain dirty political debate trick. It is a clear attempt to fake the meaning of someone else's words.

The omitted sentence reads: "As a practical matter, we can ignore the extremes of mathematical theory and use FFTs as a very practical tool. I do that too and it can work quite well in many cases. Always worth doing."

Syn08, Ovidou, or whatever you call yourself, I know you are better than that when you want to be. I have no interest in playing your political debate games when you switch to that behavior. Good day.

EDIT: For those that do want to play syn08's game, you might try doing to him what he does to you. Lie, cheat, FUD, whatever he does just see how he likes it in return. Turn it into a massive, angry political debate until the moderators close the thread.
 
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<snip>

To add insult to injury, the definition of LTI has nothing to do with "steady state measurements", so your "therefore" logic implication is simply a blow in the wind. You were clearly told what a "steady state measurement" is understood by, however you continue using your own definition to promote yet another pile of bull chips.

Nice talk, quite ...err...interesting, well written and posted with "verve". 🙂

The problem indeed is, that I was told what "steady state measurement" means; I've to admit long time ago, but luckily the teachers of the past are still present in books and so let's take a quote:

The frequency description, i. e. the determination of amplitude and phase as functions of ω, is probably the most common description in both analog and discrete-time linear shift-invariant stable systems (cf. Fig. 1.10). To obtain the frequency response of a system we can use a sinusoidal waveform with frequency ω as input and then determine or observe the output signal under steady-state conditions.

(Unbehauen,Rolf;Cichocki,Andrzej; MOS Switched-Capacitor and Continuous-Time Integrated Circuits and Systems - Analysis and Design, Springer, 34)
 
Your lie of omission by leaving out my immediately preceding sentences to the part you quoted is a well known plain dirty political debate trick. It is a clear attempt to fake the meaning of someone else's words.

The omitted sentence reads: "As a practical matter, we can ignore the extremes of mathematical theory and use FFTs as a very practical tool. I do that too and it can work quite well in many cases. Always worth doing."

Aha, so how is not quoting that distorted the message you are trying to convey in the same post, a few lines down:

However, it can also be considered not to consist of sine waves in reality, if we are concerned about certain practical problems that may be encountered.

Did I say hogwash?
 
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Try listening to ‘Trilogie de la Morte’ by Eliane Radigue.

This is a three hours long musical composition made from multiple overdubbed drones constructed entirely from transient free sine waves out of an ARP2500 synthesiser - only it does not sound like sine waves. It sounds like ethereal music from another world, and whose sonic origin is deeply within in this, our human world. It took her eight years to complete it, and as an electronic musician her understanding is that all sound is music. Having listened intently to this, her masterwork, I am now more or less entirely convinced that irrespective of its simplicity or complexity, music is made solely from sine waves.

Therefore it appears to be an equally convincing argument that sine waves can be used to map out or test any aspect of any component at every point within a recording or playback system.

Read this. ToS
 
Nice talk, quite ...err...interesting, well written and posted with "verve". 🙂

The problem indeed is, that I was told what "steady state measurement" means; I've to admit long time ago, but luckily the teachers of the past are still present in books and so let's take a quote:

(Unbehauen,Rolf;Cichocki,Andrzej; MOS Switched-Capacitor and Continuous-Time Integrated Circuits and Systems - Analysis and Design, Springer, 34)

The quote is correct; the "system" must be under steady state, not the "measurement".

Your honesty in admitting a mistake (if that's the drift of your message, I'm not sure 😀) is appreciated.
 
Forgot to address the "transient" issue; exciting a LTI system for example with a step input signal provokes a "transient process" until the system has settled (i.e. has reach the steady state) often denoted as "settling time" .

That is correct, however, there is no problem in handling the response in the frequency domain using the same-o-same Fourier transform.

What I said already (way too) many times is that if one thinks such an approach would bring anything new to the table compared to the standard approach (extending the signals by periodicity), then please come up with extraordinary proof for an extraordinary claim.

For such "transient processes" like a step response we have other much more convenient tools, namely the Laplace transform. There is a non obvious relationship between the Laplace and Fourier transforms, in that the Laplace transform for s=jw is equal to the Fourier transform if, and only if, its region of convergence contains the imaginary axis. This is also true for the bilateral Laplace transform.
 
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The quote is correct; the "system" must be under steady state, not the "measurement".

Your honesty in admitting a mistake (if that's the drift of your message, I'm not sure 😀) is appreciated.

If you hadn't recently quoted from my post

Steady state as a term is often used when describing LTI systems and by _definition_ _excludes_ _transient_ _processes.

Therefore the usual measurement using sine waves is considered as _steady_ _state_ _measurement_

your trick might have worked. 😉

But anyway, as we now all remember, what we've always have known, we seem to agree that the usual way of measuring when using sine waves (like already mentioned in my initial post to this subtopic) is a measurement in the steady state condition (i.e. steady state measurement). 🙂
 
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If you hadn't recently quoted from my post



your trick might have worked. 😉

But anyway, as we now all remember, what we've always have known, we seem to agree that the usual way of measuring when using sine waves (like already mentioned in my initial post to this subtopic) is a measurement in the steady state condition (i.e. steady state measurement). 🙂

Touche, Jakob but why waste your time?
 
Touche, Jakob but why waste your time?

It's kind of fascinating; taken syn08's trick at face value, he is now trying to state that evil Jakob (x) was FUDing with talking about "using sine waves in the usual way is steady state measurement" while totally not FUDing would have been to write "using sine waves in the usual way is measurement in steady state".

One nearly has to admire this game play..... 🙂
Overall it is a gem for friends of surrealism.
 
It's kind of fascinating; taken syn08's trick at face value, he is now trying to state that evil Jakob (x) was FUDing with talking about "using sine waves in the usual way is steady state measurement" while totally not FUDing would have been to write "using sine waves in the usual way is measurement in steady state".


FWIW, both formulations are incorrect. A correct version (although the whole context is ridiculous) would be ""using sine waves is the usual way to measure a system in steady state". Your obfuscating attempt to trivialize the matter to a potato-potatoe debate is duly noted.
 
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It's kind of fascinating; taken syn08's trick at face value, he is now trying to state that evil Jakob (x) was FUDing with talking about "using sine waves in the usual way is steady state measurement" while totally not FUDing would have been to write "using sine waves in the usual way is measurement in steady state".

One nearly has to admire this game play..... 🙂
Overall it is a gem for friends of surrealism.

I agree but I prefer my surrealism from the likes of Dali not From someone pretending to offer realism 😎

It's not a model, but you don't get that, or do you? It even holds in the acoustic domain, I hope that doesn't blow your mind 😉

Wow, you mean sound works in the acoustic domain? Hehe
I would hope any mathematical model of sound works in the acoustic domain - jeez, you are operating on some other planet, possibly one where sound is a new discovery? 😱

Seems you are alone mmerrill as Jakob didn't answer...

BTW, my example, mentioned earlier, is very simple, would you like to hear it?
I'm not interested in the physics that applies in your universe, Scott & surrealism doesn't interest me except in the art world
 
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