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Phase shift

Julf

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But even if the difference is never consciously visible, there is, nevertheless a difference: in one scene we have some 'magnificence' derived from the sheer mass of birds and the complexity of their movement. In the next, we have only 97% of that 'magnificence'. You can't put it into words, and you can't see it consciously, but one scene is less 'magnificent' than the other. If we carry on removing birds you will, at some point be able to discern the difference, but long before then you were being short changed but couldn't put your finger on it.

In this case we are not removing any birds, but slightly shifting a couple of birds that are so far away that you can't see them.

I think we have pushed the analogies way beyond the breaking point, and are totally out of phase. Your argument could be turned into "we should worry about the audible effects of the paint we use to paint our amplifiers, because it might possibly affect the sound.
 

Cosmik

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The audio equivalent of the above is two recordings of an orchestra. As the piece reaches its climax, the tympany is struck at the same moment as the piano player strikes his final note. One recording has some phase/delay shifting going on and the other doesn't. In the one with the phase shift, the tympany and piano don't quite create the solid 'step' that the correct version does. In amongst the complexity of the piece you can't notice it directly, and you certainly can't describe it, but nevertheless you are only getting 97% of the 'emphasis' of that final note. A pity.
 

Julf

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The audio equivalent of the above is two recordings of an orchestra. As the piece reaches its climax, the tympany is struck at the same moment as the piano player strikes his final note. One recording has some phase/delay shifting going on and the other doesn't. In the one with the phase shift, the tympany and piano don't quite create the solid 'step' that the correct version does. In amongst the complexity of the piece you can't notice it directly, and you certainly can't describe it, but nevertheless you are only getting 97% of the 'emphasis' of that final note. A pity.

That is of course only true if both instruments are recorded with close mics at exactly the same distance. Of course for anyone listening live, the phase relationships will vary from one listening position to other.
 
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maty

maty

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We know the phase response of NC400. We have a free soft tool like rePhase -> we can make a convolution filter that linearize only the phase and check if we notice a difference in our systems.

index.php
 
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maty

maty

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With my modded KEF Q100:

https://www.audiosciencereview.com/...inimum-phase-vs-linear-phase.8762/post-253826

index.php


index.php


The PEQ (minimum phase) of rePhase offer better sound than JRMC. And with the phase smoothing the sound is more better!

The phase smoothing has not been much but nevertheless I clearly noticed the difference. Therefore, it is very likely that I/we will notice even more in the new emulation, since the variation of the phase is greater than before and not only at 20 kHz.
 

ahofer

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Well, just to answer a question earlier:

1)
There is extensive data that indicates that under normal listening conditions, with real music, even experienced listeners have great difficulty perceiving phase effects. To quote from a recent survey paper by a top engineer at Harman International, Dr. Floyd Toole: "It turns out that, within very generous tolerances, humans are insensitive to phase shifts. Under carefully contrived circumstances, special signals auditioned in anechoic conditions, or through headphones, people have heard slight differences. However, even these limited results have failed to provide clear evidence of a 'preference' for a lack of phase shift. When auditioned in real rooms, these differences disappear.."

2)
The blind trials of the present work provide quantitative proof of this by assessing the discernability of time misalignment between signals from spatially displaced speakers. The experiment found a displacement threshold of d≈2 mm corresponding to a delay discrimination of τ≈6 μs.

Other links also suggest that the audibility is higher at low frequencies.

So, how does that translate into the Class D phase effects under discussion. We've established that the time delay is inconsequential, what about the slight phase shift above my hearing range (which tops out around 15kHz now)?
 

Julf

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So, how does that translate into the Class D phase effects under discussion. We've established that the time delay is inconsequential, what about the slight phase shift above my hearing range (which tops out around 15kHz now)?

Inconsequential as well.
 

boXem

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Well, just to answer a question earlier:

1)


2)


Other links also suggest that the audibility is higher at low frequencies.

So, how does that translate into the Class D phase effects under discussion. We've established that the time delay is inconsequential, what about the slight phase shift above my hearing range (which tops out around 15kHz now)?
In the last article you linked, the distinction between phase shift and group delay is not really clear. Reading between the lines, I believe they refer to group delay.
Anyhow, just for illustration, 6us at 20 kHz corresponds to 43 degrees phase shift.
 

Nango

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This gentleman here builds headphone amps (above the 4-digit $$$ mark and mono blocks well above 4-digit $$$ mark) with an incorporated phase shift, where he says:

"Phase shifting is small with a small phase shift from 10 to 50 hertz to compensate for the slow bass response from most headphones."

This is Europe's counterpart to Gesehlli and TCA ;) :

http://amity.de/English/products.htm
 
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maty

maty

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"Phase shifting is small with a small phase shift from 10 to 50 hertz to compensate for the slow bass response from most headphones."..


https://www.diyaudio.com/forums/solid-state/344540-alpha-nirvana-39w-8ohm-class-amp-post5958644.html
The frequency response is not linear, bass boost, because of 3.3nf.

index.php


https://www.diyaudio.com/forums/solid-state/344540-alpha-nirvana-39w-8ohm-class-amp-post5958892.html
The bass is intentional but in fact the 330k & 3.3nF in series is a frequency dependent nested feedback network, which sets the loop gain high at bass frequencies, under 100Hz, for high DF. At high frequencies, the global feedback is reduced to 15 (23.5dB).


PS: Hugh Dean always defends that GNFB must be < 29 dB - 31 dB to obtain better sound.

-> https://www.diyaudio.com/forums/aksa/294346-brand-super-aksa-saksa-85-a-6.html#post4878481

5. Feedback has an effect on the sound quality...
 
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Julf

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PS: Hugh Dean always defends that GNFB must be < 29 dB - 31 dB to obtain better sound.

A statement like that makes no sense at all.

5. Feedback has an effect on the sound quality...

Of course. The more the better.
 
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maty

maty

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Off topic

Talking about the bass boost, with my little coaxials (new: 49 Hz at -3 dB) with my ferrite mod only I need a very slightly boost.

Rephase-PGEQ-KEF-q100-bass-boost-cut.jpg
 
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maty

maty

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[PDF] https://www.kiiaudio.com/media/GENERAL/docs/manuals/kiithreemanualpressv30.pdf

page 42

Kii-Three-latency-DSP-correction.png

(Full phase correction means, that the whole frequency spectrum radiated by the speaker does not have any un-natural phase shift, an artefact that is commonly induced by classical analogue crossovers. Clever DSP correction allows us to instead achieve a phase response that is identical to the original signal on the recording.


The same must be aplied to the amplifier and its phase graph, as it is logic.
 

Julf

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The same must be aplied to the amplifier and its phase graph.

As we keep pointing out, you are confusing frequency-dependent phase shifts and frequency-independent time delay.
 
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maty

maty

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I will try to explain myself better. The die-hard lovers of the measurements defend that the amplifier acts as a simple cable but with gain, that is, that it does not alter the signal at its input except in amplitude.

This must also include the phase, which must always be constant in the audio band.
 
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maty

maty

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DonH56

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I will try to explain myself better. The die-hard lovers of the measurements defend that the amplifier acts as a simple cable but with gain, that is, that it does not alter the signal at its input except in amplitude.

This must also include the phase, which must always be constant in the audio band.

For ideal time response the phase must be linear with frequency so that group delay (not phase) is constant.
 
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maty

maty

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It is what I have been saying from the beginning. That is fixed, constant ... that phase does not vary with the frequency -> linear, FLAT, ideally 0º in ALL audio band.

It has always been that way and a new amplification technology should respect it.

Imagine an audio chain in which the source, the preamp and the amplifier each vary the phase with the frequency ... We have to eliminate variables from the equation and not to add a new one.
 
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