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

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U101222

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maty tinman said:
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 70º at 20 kHz!
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This is fantastic. The phase shift of the 700AS2 is about 35º 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
 
maty tinman

maty tinman

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mocenigo said:
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...
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Equalization (audio) - Wikipedia

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.
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Less sensitive but still sensitive to the phase modification.


Linear Phase EQ vs Minimum Phase EQ — Pro Audio Files

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)...
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How much affect with IcePower 1200AS2? I do not know.
 
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maty tinman

maty tinman

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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.


E7E3E943-331F-4DF1-AA88-843E7B30702F.jpeg

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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 < 45º ?

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.

​
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 -​
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maty tinman

maty tinman

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Hypex NC400 - frequency/phase graphs

Amirm has measured the frequency/phase response of Hypex NC400 at my request. When it is possible, with the NC500 and others.

After correctly setting the very expensive AP analyzer, with external AES-17 filter.

Review and Measurements of Hypex NC400 DIY Amp | Page 11 | Audio Science Review (ASR) Forum

index.php


Review and Measurements of Hypex NC400 DIY Amp | Page 12 | Audio Science Review (ASR) Forum

There are actually two types of AES-17 filters for Audio Precision analyzers.

* One is internal and is designed to give you the standardized bandwidth for general work. That filter is NOT sufficient for class-D amplifiers, nor delta-sigma DACs with a lot of noise shaping. These products have such high slew rate that they screw up the front-end of the analyzer, resulting in erroneous THD measurements and may even confuse the auto-scalar.

* For these measurements, you must use the external, passive AES-17 filter as I have been using...
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Well, there are phase shift but much less than IcePower 1200AS2, 700AS2 or Pascal M-Pro modules. Better engineering with frequency/phase in Hypex NC400.
 
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BYRTT

BYRTT

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Joined 2009
Hi maty,

Phase for NC400 is probably textbook in it looks follow amplitude response (bandwidth) as a minimum phase device, below is nearly the same slope in a Rephase textbook example for a 1st order low pass at 54kHz, a close number to what NC400 datasheet tell about having a -3dB point at 50kHz so we close and should not worry other than some users would always wish or prefer for more bandwidth.
 

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maty tinman

maty tinman

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If you do not urge, I would expect Amirm to measure a NC500.

* NC400 at 20 kHz - about 17 degrees

* Anaview AMS1000 at 20 kHz - about 22 degrees.

The problem, I think, is in the IcePower 1200AS2, with much more degrees.

I still do not know if with acoustic music and natural voices we can appreciate the shift phase. I suspect that yes but I have not been able to verify it myself or found information on the net in one way or another.

If you listen to other kind of music, it will surely be difficult to notice differences.
 
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U130421

Disabled Account
Joined 2015
I find confusing of what you are wondering about . The first curves posted for 1200as2 is the output impedance curves . Impedance means resistance and reactance components determined by phase angle . At 45° they become equal each being 0.707 of the impedance value which is about 7m ohm . That is the output of the amplifier the speaker sees it as a 5m ohm resistor in series with 0.45uh inductor . Just a wire of 1m linking the speaker will add 0.1 ohm in series to this impedance making it almost resistive .
 
NMOS

NMOS

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Eva said:
Opera and the like are too filled with references to bogus content of ancient cultures and power/gender/money/class conflicts often not possible to solve within that performance format. The dramatized, exaggerated and flavored exposition in full length of some mistakes of the past of the human race can be forgotten, once the synthesized version is done.

Live electronic music is made with synthesizers, computers and crowd feedback. The raw function of music is to connect people and nature. The sense of music event as a religious tribal-bounding cult is restored.

The problem with Opera is that most of them "learned" by paying a prostitute (scam, can't learn anything on top of irrational experience).

"High-End" means that the technology resembles a higher purpose (one that has been slowly developing for a long time), which can only be understood by studying the technology and the creators.

Electronic music has recordings in all sorts of qualities. There is plenty of transient information at all frequencies. While electronic music can sound barely OK with junk systems, there is usually one more level of detail only appreciable under the right human and technical conditions. Some can argue "the kids do not understand that", but the kids are hooked to electronic music (like hell) seeking for that. Emotional connection is not as good when frequency ranges are missing, leading or lagging. Voice is a more ample concept than just human voices. Synthesizers can be heard as non-human voices.

Be careful with dopamine because this is the cheapest to manufacture neurotransmitter in cells. Dopamine by itself is not high end, but it is an ingredient in more complex processes requiring several messenger substances, which can be high end.
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EVA I like underground music and partys,....and big power amps for drving large subwooder to feel bass

EVA can I ask you how old are you ?
 
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Octavia

Member
Joined 2008
Eva all you say is thought provoking and I like the ideas and feelings of high end and higher meanings converging. In some ways it's reminding me of some personal conversations with Siegfried Linkwitz bless his departed soul. Back to amplifiers, any comments on the TPA3150 or maybe something else that you might consider ?
 
jan.didden

jan.didden

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