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Topping PA5 Review (Amplifier)

Holmz

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What Amir mentions in the video I linked to is the "phase soup" that takes place in a normal listening room, due to all the reflections in the listening room.

That would indicate that one (like Amir) cannot effectively measure phase in a room then.
But if one measured it in free space then they could… there would be no soup, stock or broth.

It also means that the reflected SPL is higher for a more omnidirectional speaker, and less for a more narrow beamed speaker.

And if we did not hear the direct sound first and separate from reflections, then it means that we could probably turn the speakers towards walls/corners and they would sound the same? Which seem preposterous.

I doubt that a slow change of phase versus freq in an amplifier would be audible, but I dunno.
 
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amirm

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And if we did not hear the direct sound first and separate from reflections, then it means that we could probably turn the speakers towards walls/corners and they would sound the same?
Direct sound arrives first and due to precedence effect, has strong power in establishing the tonality of the speaker. So no, you can't turn the speaker around and expect it to sound the same. You would be hearing the rear radiating on-axis sound which is mostly low to mid frequencies.
 

daniboun

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Hi amigos,

just to share. Here a picture of the Air Core inductors of next Allo TPA3255
The design will be different in its final version, without a doubt even


 

jlesterp

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Direct sound arrives first and due to precedence effect, has strong power in establishing the tonality of the speaker. So no, you can't turn the speaker around and expect it to sound the same. You would be hearing the rear radiating on-axis sound which is mostly low to mid frequencies.
How about reversing the tweeter's polarity relative to the woofer. It definitely has an audible effect (worst case phase shift on high frequencies).
 

Moosi

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Is there any way to add a simple, small display with a vol. scaling to this amp ? I'm really used to tuning in exact volume numbers at different times of the day.
 

TimF

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Many questions about whether the effect is sufficient in PA5. How much effect can be needed when playing music with a lot of dynamics? Here this video maybe can give some guidance:


No wonder there is usually talk of a headroom when it comes to power and amplifiers.Although it is clear if you play music that is very compressed, no peaks or valleys but more of a smooth porridge, it does not place such high demands on the amplifier. Which, incidentally, is mentioned in that video.:)

Regrading how much ampl. power I need for the dynamics let me admit that I often sit with the remote in my hand to turn down the volume in the loud passages. I sometimes like great dynamics but most of the time I like lessor dynamics to be honest. I know some sections of music are meant to shake the barn but I don't most of the time want my living room so shaken so I briefly turn down the volume. Am I the only one. I find it surprising that so many of you out there in internet land like your music at 80, or 85, or 90 or decibels. I'm a wienie I guess.
 
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Moosi

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I'm a wienie I guess.
No. You're suffering from some form of sibilance that makes it tough on your ears to listen for longer periods on loud vol. Try better gear or upsampling to high DSD levels.
 

DanielT

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Regrading how much ampl. power I need for the dynamics let me admit that I often sit with the remote in my had to turn down the volume in the loud passages. I sometimes like great dynamics but most of the time I like lessor dynamics to be honest. I know some sections of music are meant to shake the barn but I don't most of the time want my living room so shaken. I briefly turn down the volume Am I the only one. I find it surprising that so many of you out there in internet land like your music at 80, or 85, or 90 or decibels. I'm a wienie I guess.
Everyone can listen in any way they want, of course. If you get tired of listening to dynamic music, at a fairly high volume well I do not know if I should mention it. You may have a really good system, but distortion (clipping) can be quite irritating to the ears.

As an example, the receiver you see in the pictures I bought this weekend at a flea market for a few dollars. It works but damn what a pain in the ears I get when I listen to it. I will immediately return it to some charity flea market. Whoever then buys it does a good deed. For others, that is, not for his own ears, on the contrary in that case.

Tips test really bad Hifi so you realize what decent Hifi can do.:)

Edit:
Regarding Philipsen. It is possible that it would sound better if it was serviced, capacitors were replaced and so on. Nothing I intend to do with it. I sprayed pots with electronics spray and motinated them but more than that I do not do with it.
(no imagination, if I could not dot that Philips in a blind test I would eat my hat)
 

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pma

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What if the amp in question has a significant phase shift in the high frequencies, can it affect some speakers with complex crossovers that will lead to frequency response difference?
Significant phase shift means quite big deviation in amplifier amplitude response. So it will be audible change in “amplifier sound”. As amplifier phase response will be most probably smooth near speaker crossover frequency, the speaker will not be “affected”.
 
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amirm

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How about reversing the tweeter's polarity relative to the woofer. It definitely has an audible effect (worst case phase shift on high frequencies).
That screws up the crossover frequency response.
 

KSTR

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Reversing tweeter polarity effect depends on crossover type. In a crossover with close to 90 degrees phase offset between drivers (symmetric odd order acoustic XOs, often seen in W-T-W arrangements), the frequency response remains effectively unchanged but the phase response is changed. Typically not very audible as the XO freq is high (both channels flipped, of course). In a woofer-to-midrange XO it's audible sometimes.

But this is all excess phase stuff (allpass function), not minimum phase as for amplifiers.
 

jlesterp

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Significant phase shift means quite big deviation in amplifier amplitude response. So it will be audible change in “amplifier sound”. As amplifier phase response will be most probably smooth near speaker crossover frequency, the speaker will not be “affected”.
Do some amplifiers have worse phase response relative to their amplitude response or are the amps mostly have the same deviation from FR and phase response? (disregarding all pass filtering) How much deviation is there in phase response that would cause spatial or audible difference in the speakers?

So if FR is unchanged, then there would be no audible difference in phase response in the HF? I just want to learn here.
 

pma

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Do some amplifiers have worse phase response relative to their amplitude response or are the amps mostly have the same deviation from FR and phase response? (disregarding all pass filtering) How much deviation is there in phase response that would cause spatial or audible difference in the speakers?

So if FR is unchanged, then there would be no audible difference in phase response in the HF? I just want to learn here.

Please take into account that it depends on load complex impedance and amplifier circuit topology. Please let me answer you by measurements of amplitude frequency response and phase frequency response of a conventional class AB amplifier vs. TPA3255 AIYIMA A07 - and think about it. If more discussion is needed, a separate thread would be an option, I can paste my measurements there. Is this audible in a DBT test? Yes, not easily, but with better than 5% uncertainty. Is this because of phase response? Just related to, as a derived parameter. Can we read this from 4/8 ohm resistive response? With difficulties.

classAB_amplitude_phase_response_dummyload.png


classD_amplitude_phase_response_dummyload.png


P.S.: new plots with soundcard FR elimination
 
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voodooless

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I can paste my measurements there. Is this audible in a DBT test? Yes, not easily, but with better than 5% uncertainty. Is this because of phase response?
Probably not. It should be trivial to take some audio files and make two variants:
  • A: only reproduce the amplitude response you measured.
  • B: only reproduce the phase response you measured.
Then ABX those two against the original. I'm pretty sure A will be possible, B will not.
 

pma

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Probably not. It should be trivial to take some audio files and make two variants:
  • A: only reproduce the amplitude response you measured.
  • B: only reproduce the phase response you measured.
Then ABX those two against the original. I'm pretty sure A will be possible, B will not.
Definitely yes. The test was already posted, half a year or more ago. Please try to find it, with the ASR search engine. The result was positive, with audible difference proven.
P.S.: amplitude and phase response cannot be separated, it would be a nonsense. They are related through Hilbert transform, as I already explained ( yesterday).
 

voodooless

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The test was already posted, half a year or more ago. Please try to find it, with the ASR search engine. The result was positive, with audible difference proven.
Yes, you tested A + B together, not these factors separately as far as I know. The question is: which one of the two is audible in this case: phase or amplitude. Or did I totally miss that test?
 

xrk971

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If you don’t think phase is audible flip polarity of one speaker for 180deg. That’s an extreme case I know but despite a room having reflections, the direct sound from the speaker is very important. Even on non bass heavy content music the “phasiness” is instantly detectable (it is in the 1kHz to 6kHz range). I can tell when speakers are accidentally flipped with ears instantly.
 
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