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Class D Switching Power Amplifiers and Power D/A conversion

Phase shift in class D amplifiers. How it affects the sound?
Phase shift in class D amplifiers. How it affects the sound?
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Old 17th April 2018, 09:21 AM   #1
maty tinman is offline maty tinman  Spain
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Default Phase shift in class D amplifiers. How it affects the sound?

Two days ago I was reviewing, again, the manual of the new IcePower 1200AS2 class D module and I was struck by this graph, where the phase shift is almost 70 at 20 kHz!
76489414-30CE-471E-BC96-F9DD04C23DC1.png

Hypex NC500 only says:
Quote:
Output coil inductance: 10 uH Effective output inductance ithis number divided by loop gain.
Is it usual in this type of amplification? Taking into account that the phase also varies -except specific filters- in the speakers, how does it affect sound at high frequencies?

KEF LS50
D4DDA375-AFB8-4B35-AF3F-FAE9F3D73297.jpeg

KEF Q100
EDD10C23-B65A-438A-AD91-565E054D23EF.jpeg

Last edited by jazbo8; 17th April 2018 at 10:27 AM. Reason: images
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Old 17th April 2018, 09:32 AM   #2
JonSnell Electronic is offline JonSnell Electronic  United Kingdom
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I would ask Bang & Olufsen as it is their trade name and design.
I suspect the phase shift makes little difference at Ultra Sonic frequencies, say above 18kHZ as we cannot hear them.
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Old 17th April 2018, 09:33 AM   #3
maty tinman is offline maty tinman  Spain
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At 2 kHz the shift is 50.
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Old 17th April 2018, 09:55 AM   #4
maty tinman is offline maty tinman  Spain
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About - ICEpower


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Hi from Spain,

I just open a thread about the phase shift in Icepower 1200 AS2.

Phase shift in class D amplifiers. How it affects the sound?

[ Two days ago I was reviewing, again, the manual of the new IcePower 1200AS2 class D module and I was struck by this graph, where the phase shift is almost 70 at 20 kHz!

[IMG] http://maty.galeon.com/WP-imagenes/h...ance-phase.png

...Taking into account that the phase also varies -except specific filters- in the speakers, how does it affect sound at high frequencies

- maty -
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Old 17th April 2018, 02:00 PM   #5
maty tinman is offline maty tinman  Spain
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Phase, Time and Distortion in Loudspeakers

http://sound.whsites.net/ptd.htm#s4

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4 - Phase Audibility

The audibility of absolute phase is nil.

Quote:
From 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 ..." [4]
... There have been many tests and experiments to look at phase shifts within the audio band, and whether they are audible. Under controlled laboratory conditions (or using headphones), there is strong evidence that with single (complex) tones, there is an audible change. However, in a listening room with speakers reproducing music, there is little evidence that phase shifts are audible with the vast majority of recorded material...
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The second version of the all-pass network gives a completely different waveform, simply because the phase varies from 0 at low frequencies to 180 at high frequencies.

Click the image to open in full size.

Note that this particular class of filter is called 'all pass' - it passes all frequencies equally (i.e. the magnitude is unaffected). Not much of a filter by normal standards, but a useful tool nonetheless. Interestingly, if the input and output of an all pass filter are summed, the result is an ordinary filter. High and low pass responses are available. Not that there is a great deal of point, since this is vastly more complex than a 6 dB/ octave filter built conventionally. I just thought I'd mention it - someone might be interested :-)
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Old 17th April 2018, 02:47 PM   #6
IVX is offline IVX  Ukraine
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I would like to offer an experiment about audibility the phase lag in highs. We need any DSP with 1st order all-pass filter with F=40kHz(Fs=>96Khz, 20khz will be also about -70deg), and golden ears. I know, I'll not hear the difference.
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Old 17th April 2018, 06:57 PM   #7
lespaul1963 is offline lespaul1963  United States
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Im an old school rocker who destroyed his hearing on stages in pubs and clubs over the decades with a 100 watt Marshall head and a pair of 4x12 cabinets. Adequately powered, quality PAs in these smaller venues were unheard of prior to the mid to late 90s, hence the need for the Marshall flamethrowers. My point is that I need hearing aids in order to hear much anything above 2 kHz. I switched to bass a few years ago and while Im using a 500 watt Class D amp and a 4x10 cab, because bass freq are more power dependent, Im not creating the insane sound pressure levels. Also I am a light touch bassist, so all that clean headroom is so that I dont have to beat my strings like they owed me money. Point being is that Ive never noticed any unpleasant phase shift artifacts even at 2 kHz where I still can kinda hear naturally. I noticed the article that states the ability of the human ear to adapt. I can attest that I find the proposition to be true.
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Old 17th April 2018, 07:03 PM   #8
scottjoplin is offline scottjoplin  Wales
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Hi, lespaul, to which article do you refer?
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Old 17th April 2018, 08:04 PM   #9
lespaul1963 is offline lespaul1963  United States
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scottjoplin....I posted a reply to you but it’s not showing. Let’s see if it appears.
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Old 17th April 2018, 08:36 PM   #10
nigelwright7557 is offline nigelwright7557  United Kingdom
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Quote:
humans are insensitive to phase shifts
Humans use phase shift to know what direction a sound is coming from.
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