Here's a probably misplaced spanner.
Whilst you lot are discussing the nuances of phase shift in Class D amplifiers I'm left wondering about current slew rate in the output filter inductor.
Let's say it can just support a full peak to peak 20KHz sine wave with nothing else going on.
Now add in a 500Hz tone for that to ride on top of.
Current slew rate in the inductor is limited by the volts you can place across it.
Take +/-50V rails. Inductor is happy with 20KHz on its own. Now put in the 500Hz at +/-25V. At plus 25 volts the inductor can only get an extra plus 25V across it swinging positive but 75V across it negative.
How does that affect how the amplifier might reproduce the 20KHz tone?
Whilst you lot are discussing the nuances of phase shift in Class D amplifiers I'm left wondering about current slew rate in the output filter inductor.
Let's say it can just support a full peak to peak 20KHz sine wave with nothing else going on.
Now add in a 500Hz tone for that to ride on top of.
Current slew rate in the inductor is limited by the volts you can place across it.
Take +/-50V rails. Inductor is happy with 20KHz on its own. Now put in the 500Hz at +/-25V. At plus 25 volts the inductor can only get an extra plus 25V across it swinging positive but 75V across it negative.
How does that affect how the amplifier might reproduce the 20KHz tone?
Phase shift is not a tone buddy
You cannot hear a phase shift at all
You can only feel when multiple channel have cancellation because of difference phase coming to your ear.
Slew rate is property of linear amplifier not class D.
For class D, it can produce any desired wave without facing problem like low slew rate at linear amplifier.
Perhaps I should have been more precise, the effect of phase shift across the spectrum can be audible.Phase shift is not a tone buddy
You cannot hear a phase shift at all
You can only feel when multiple channel have cancellation because of difference phase coming to your ear.
Why would 18 degrees be acceptable? Or 41 not? Can you hear it? Is it an important parameter?
I doubt it could ever be heard - as long as you listen through a medium like air, there are rotations which depend linearly on the frequency and the distance. A violin sounds like a violin whether you are 1 m or 5 m away. Yet the various spectral components of the sound have different phase rotations when they arrive at you ear.
Phase rotations in amplifiers may be correlated to other parameters (transient response?) but per se are not audible, except perhaps for a impression of different distance from the scene. if two channel have a phase rotation imbalance, it is a different thing.
Then of course there are the insane folks at ASR which only judge according to measurements. They provide useful information but tend to overstate its relevance. This said, I expect that good engineering will measure well, where it counts.
Roberto
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Linear phase shift across the spectrum MIGHT be psychoacustically related to perceived “distance” and therefore explain why some preamps, amps, speakers sound more “forward” than others. Apart from this, I cannot think of other consequences. I am not aware of studies of this.
Roberto
Possibly, Nelson's H2 apparently can manipulate depth by phase reversal of the harmonic distortion, but that's an extreme example and maybe more to do with tonal balance. Change of amplifiers' transfer function appear to effect the sound, have you seen PMA's thread linked to a few posts back?
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Maybe why Marshall sold millions of 4 by 12 inch cabs with speakers right next to each other ?
When I ran a mobile disco I kept my pair of speakers at most 6 feet apart.
Sorry but that is not precise enough.
Phase shift is audible when it has big enough angle shift and when phase shift is occured among each of multiple speakers at the same tone and time so that cancellation is happened.
Multiple speakers for guitar amplifier is choosen by designer to achieve very very specific tone color or called as timbre.
Exsctly that is.
Distance in sound engineering is Phase shift!
Beside the sound equipment itself.
In this case the concern is sound pressure. When we have many speakers then as phase shift is always there then we should find the maximum sound pressure for audience by considering phase shift by distance. Nothing more other concern than that.
What do you think could be causing the differences people are hearing here?
Can you hear a difference between 2 solid state preamps?
That is two different equipment maybe produce different phase shift at the same time. It can be audible if both has enough phase shift difference.
My concern is people might be missunderstanding in approaching phase shift in audio system. Mainly misconcept which lead to wrong judgement to class D.
VERIFIED.
I can hear very easy the phase shift of Hypex NC400. I had emulated with rePhase. The sound is worse without any doubt. Without life. Rocket man, from Diamonds (2017), by Elton John, vinyl of course. With my modded KEF Q100 5.25" coaxial speakers.
I can hear very easy the phase shift of Hypex NC400. I had emulated with rePhase. The sound is worse without any doubt. Without life. Rocket man, from Diamonds (2017), by Elton John, vinyl of course. With my modded KEF Q100 5.25" coaxial speakers.
It reminded me of the difference I appreciated when I used a linear phase PEQ instead of a minimum phase PEQ, much better with the last.
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Years ago, when I researched, I already discarded the new Hypex NC. I thought the IcePower 1200AS would be the chosen ones until I see the very ugly phase response > 1 kHz.
For the tweeter, aka HF, I prefer to avoid the previous ones and others.
I have captures of my emulation with rePhase. The difference was so noticeable that I needed very few seconds. Recording with acoustic and electrified instruments, without Autotune.
Modern commercial recordings with synthesized instruments and Autotune are other world. Surely there it will be much more difficult to appreciate differences, if any.
For the tweeter, aka HF, I prefer to avoid the previous ones and others.
I have captures of my emulation with rePhase. The difference was so noticeable that I needed very few seconds. Recording with acoustic and electrified instruments, without Autotune.
Modern commercial recordings with synthesized instruments and Autotune are other world. Surely there it will be much more difficult to appreciate differences, if any.
KEF Q100, 5.25" coaxial speaker. True 85 dB, minimum 3.9 Ohms.
Phase and impedance
Hypex NC 400
SPL and phase
Phase and impedance
An externally hosted image should be here but it was not working when we last tested it.
Hypex NC 400
SPL and phase
An externally hosted image should be here but it was not working when we last tested it.
My KEF Q100 with rePhase.
[Big IMG, link] http://maty.galeon.com/WP-imagenes/kef-q100/Rephase-PPEQ-KEF-q100.png
Same speakers emulating the Hypex NC400 phase.
[Big IMG, link] http://maty.galeon.com/WP-imagenes/...-KEF-q100-with-Hypex-NC400-phase-response.png
PS: from yesterday I do not have the 40 Hz boost. Too much bass yesterday, to confirm with more recordings. 0 dB -> 0.4 dB -> 0.6 dB and now 0 dB again.
An externally hosted image should be here but it was not working when we last tested it.
[Big IMG, link] http://maty.galeon.com/WP-imagenes/kef-q100/Rephase-PPEQ-KEF-q100.png
Same speakers emulating the Hypex NC400 phase.
An externally hosted image should be here but it was not working when we last tested it.
[Big IMG, link] http://maty.galeon.com/WP-imagenes/...-KEF-q100-with-Hypex-NC400-phase-response.png
PS: from yesterday I do not have the 40 Hz boost. Too much bass yesterday, to confirm with more recordings. 0 dB -> 0.4 dB -> 0.6 dB and now 0 dB again.