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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 14th May 2018, 03:09 PM   #61
mocenigo is offline mocenigo  Germany
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Quote:
Originally Posted by maty tinman View Post
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!
This is fantastic. The phase shift of the 700AS2 is about 35 at 20Khz, yet an old acquaintance of ours once wrote "I have the latest and greatest Icepower 700AS amp sitting right here beside the new 502MP Hypex Ncore. Personally I wouldn't use the Icepower for any more than sub duty. Way too much phase shift in the top end. It just sounds wrong." See: Benchmark...first watt....ABX...facepalm! | Page 4 | Audio Science Review (ASR) Forum

Funny thing is, the 1200AS2 has double that phase shift, yet he is selling this as the killer class D module, better for everything. He did not claim it should be ok only for sub duty.

However, what is important is that the phase relation between the two speakers for the same frequency is preserved, for the brain to help detect the position of an object, and this should be ok.

Roberto
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Old 14th May 2018, 03:32 PM   #62
mocenigo is offline mocenigo  Germany
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Originally Posted by maty tinman View Post
In Spanish there is a saying: quien calla otorga -> who keeps silent says yes.
"Chi tace acconsente" in Italian.
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Old 14th May 2018, 04:19 PM   #63
maty tinman is offline maty tinman  Spain
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Default ICEpower 700AS2

ICEpower 700AS2 page 18

[PDF] https://icepower.dk/download/1624/

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Old 14th May 2018, 04:46 PM   #64
maty tinman is offline maty tinman  Spain
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Quote:
Originally Posted by mocenigo View Post
However, what is important is that the phase relation between the two speakers for the same frequency is preserved, for the brain to help detect the position of an object, and this should be ok...
Equalization (audio) - Wikipedia

Quote:
In addition to adjusting the relative amplitude of frequency bands, an audio equalizer may alter the relative phases of those frequencies. While the human ear is not as sensitive to the phase of audio frequencies (involving delays of less than 1/30 second), music professionals may favor certain equalizers because of how they affect the timbre of the musical content by way of audible phase artifactst.
Less sensitive but still sensitive to the phase modification.


Linear Phase EQ vs Minimum Phase EQ — Pro Audio Files

Quote:
Analog EQ

With any analog equalizer, the bands being boosted or cut are subject to phase-shifts due to the latency created by the change in amplitude within that band in relation to unaffected bands. This is unavoidable, but manufacturers try to reduce the amount of phase-shift as much as possible (unless it produces a pleasing or characteristic sound), thereby calling these sets of equalizers ‘minimum-phase.’

Digital EQ

Most digital equalizers have algorithms that are modeled after minimum-phase equalizers, due to their prominence in the analog world, their lack of plug-in latency issues, and in the big market for analog replication. These algorithms are digital, so obviously different from the get-go, but are meant to mirror the process of the analog latency and wide bands, and then its subsequent recovery, thus keeping with the minimum-phase concept.

Linear Phase EQ

The way that the equalizer algorithms are configured are completely different for linear-phase equalizers.

Linear-phase is exactly how it’s described: linear. For the varying wavelengths of varying frequencies, linear-phase equalizers adjust phase accurately to the degree of zero phase-shift. This can only be achieved digitally with such accuracy. This non-existent phase shift, leaves the actual amplitude of the waveform almost unchanged in many instances where a minimum-phase equalizer may cause drastic amplitude changes (depending upon the degree of phase shift).

This outcome allows linear-phase equalizers to affect the harmonic character without much change in overall level, making them ideal for mastering practices (which is why they tend to be marketed toward mastering engineers)...
How much affect with IcePower 1200AS2? I do not know.

Last edited by maty tinman; 14th May 2018 at 04:50 PM.
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Old 17th May 2018, 08:27 AM   #65
maty tinman is offline maty tinman  Spain
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I just received the answer. They say that is not the module amplitude and phase response.

They do not provide what is.

But, you know, a poweramp is like a black box system. You can modelate it.

In class A or class AB the output impedance is almost resistive. It usually varies in a range of six degrees. You know, Engineering is the science of what is possible (or reasonable).

The question is in class D the output impedance is not only resistive!

How does it alter the phase of traditional dynamic loudspeaker systems, with phase < 45 ?

That is why in the first post I put the impedance and phase graphs of two: KEF Q100 (mine) and KEF LS50.

I trusted that, being the other parameters of this 1200AS2 class D module so excellent / superb, that said phase would hardly vary in f < 20 kHz.

Now we have a new variable in the equation in front class A or class AB.

How will it affect the sound quality? I do not know.


*********** ************

At least IcePower has responded to my emails unlike the audiophile PS Audio on its questionable implementation of the Icepower 700AS2 modules in other forum (very audiophile forum).

Right now I answer the IP mail with this link in case they want to reply.

Quote:
Thank you for your answer but you do not provide the correct graph.

I had write about your answer here:

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

- maty -

Last edited by maty tinman; 17th May 2018 at 08:42 AM.
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Old 23rd May 2018, 08:40 PM   #66
Destroyer OS is offline Destroyer OS  United States
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Phase shift in class D amplifiers. How it affects the sound?
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Originally Posted by maty tinman View Post
Which companies design high quality class D amplifiers?
Please, Eva, do tell. I'm curious which manufacturers meet your criteria.
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