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Time Domain measurements?

haraldo

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Was there any discussion of phase shift in amplifiers, isn't this a major and neglegcted issue?
Is it the mainstream idea that whatever happens in an amplifier above 20KHz is of no interest?

According to a whitepaper I read by Cyril Hammer at Soulution Audio, he states following:
- an amplifier with a bandwidth of 20 KHz (-3dB) has a phaseshift of 45 ° at 20 KHz, very audible.....
- an amplifier with a bandwidth of 200 KHz (-3dB) has a phaseshift of 6 ° at 20 KHz, audible
- an amplifier with a bandwidth of 2MHz (-3dB) has a phaseshift of 1 ° at 20 KHz, not audible

There must be a reason why Soulution settles for an bandwidth in their amplifier boards of 30 MHz (according to Mr. hammer) and that they aim for 2 MHz bandwidth for their best poweramps, to my ears in general, the ultra high bandwith amps like Soulution 511 is just plain better... I never heard the CH Precision, Audionet, Goldmund amps that I believe all of them are extremely high bandwidth... more products that follow these lines :rolleyes:

I don't remember seeing any serious scientific talks on these things in forums ....
Maybe I haven't looked well enough around :)
 
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RayDunzl

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Was there any discussion of phase shift in amplifiers, isn't this a major and neglegcted issue?

My amp, 5W into speakers

Claimed .1Hz to 240kHz, +0 -3dB

Top - frequency response
Bottom - phase

7.73 degrees at 20Hz, 1.38 degrees at 20kHz

Analysis: not major nor, now, neglected.

As for audibility, no opinion.

1595706016178.png
 
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tuga

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Was there any discussion of phase shift in amplifiers, isn't this a major and neglegcted issue?
Is it the mainstream idea that whatever happens in an amplifier above 20KHz is of no interest?

According to a whitepaper I read by Cyril Hammer at Soulution Audio, he states following:
- an amplifier with a bandwidth of 20 KHz (-3dB) has a phaseshift of 45 ° at 20 KHz, very audible.....
- an amplifier with a bandwidth of 200 KHz (-3dB) has a phaseshift of 6 ° at 20 KHz, audible
- an amplifier with a bandwidth of 2MHz (-3dB) has a phaseshift of 1 ° at 20 KHz, not audible

There must be a reason why Soulution settles for an bandwidth in their amplifier boards of 30 MHz (according to Mr. hammer) and that they aim for 2 MHz bandwidth for their best poweramps, to my ears in general, the ultra high bandwith amps like Soulution 511 is just plain better... I never heard the CH Precision, Audionet, Goldmund amps that I believe all of them are extremely high bandwidth... more products that follow these lines :rolleyes:

I don't remember seeing any serious scientific talks on these things in forums ....
Maybe I haven't looked well enough around :)

Spectral also advocates ultra-wide bandwidth amplifiers.
 

Lbstyling

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I have spent quite some time over lockdown using RePhase software on my digital active speakers.

I cannot hear any obvious effect of phase change when it is slow changing across decades, and all drivers doing it (as with passive speakers and amplifier phase drift), but correcting for phase/time allignment does yield considerable improvements when the drivers do not otherwise track each other well (my mid driver rises to 45deg out by 400hz) Even when they are EQ'd flat independently and re-EQed globally, Its clearly inferior.

I assume this is actually an off axis spl difference though, as if the drivers are not in phase on axis, I assume when under dynamic conditions (breakup for instance), they may sum differently off axis.

There's no way I'm doing the research to get to the bottom of that though! Happy to just use RePhase!
 

DonH56

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Was there any discussion of phase shift in amplifiers, isn't this a major and neglegcted issue?
Is it the mainstream idea that whatever happens in an amplifier above 20KHz is of no interest?

According to a whitepaper I read by Cyril Hammer at Soulution Audio, he states following:
- an amplifier with a bandwidth of 20 KHz (-3dB) has a phaseshift of 45 ° at 20 KHz, very audible.....
- an amplifier with a bandwidth of 200 KHz (-3dB) has a phaseshift of 6 ° at 20 KHz, audible
- an amplifier with a bandwidth of 2MHz (-3dB) has a phaseshift of 1 ° at 20 KHz, not audible

There must be a reason why Soulution settles for an bandwidth in their amplifier boards of 30 MHz (according to Mr. hammer) and that they aim for 2 MHz bandwidth for their best poweramps, to my ears in general, the ultra high bandwith amps like Soulution 511 is just plain better... I never heard the CH Precision, Audionet, Goldmund amps that I believe all of them are extremely high bandwidth... more products that follow these lines :rolleyes:

I don't remember seeing any serious scientific talks on these things in forums ....
Maybe I haven't looked well enough around :)

It has been discussed. I doubt you'll find any amplifier today that specs -3 dB at 20 kHz; they all have much greater bandwidth than that. I am curious how audibility of the phase shift was determined. Most folk cannot hear 20 kHz with or without phase shift. The phase shift depends upon the topology, number of poles and zeros in the transfer function, and so forth. You could generate much less phase shift using the right filter topology. Having several (or many) MHz of bandwidth adds noise and can cause stability problems. Normal design practice is to provide enough for the job and no more; excess (let alone excessive) bandwidth introduces more problems. I do not see the need for 30 MHz bandwidth in an audio amplifier unless it also serves as an RF amplifier for a HF ham station or whatever. You need enough bandwidth to provide closed-loop stability and enough slew rate to prevent distortion, but that takes maybe a decade, or 200 kHz, not MHz of bandwidth.

It is not a neglected issue; it is one that was solved long ago and thus does not warrant significant discussion now.

IMO - Don
 

Joachim Gerhard

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I general in Germany we have a long tradition to build power amplifiers with a wide bandwidths. Early AudioLabor, Burmester and Omtec are examples. In England it is the other way around. Folks like Quad have claimed that there is no useful information over 20 kHz and there is even dirt out there that we do not want in our audio. The commercial realty is that both camps can not claim any supremacy what sold best and I am not aware of any study that provides enough evidence that one aproach is better then the other. Ncore and Purifi, highly praised here, have bandwidth limiting by nature to suppress the switching artifacts. TIM and Phase Modulation can be avoided by bandwidth limiting curiously.
you can study the work of Bob Cordell on this.
i have not decided too. I have a newer QUAD poweramp that has -3dB at 50kHz and sounds fine and also a super high speed power amp prototype that goes to 10MHz I like too. I have limited the input though to -3dB at 500kHz .
One guy i asked is Nelson Pass. In his inimitable way he said : some of my amps have high bandwidth, some don’t.
I just want to add that technical it is no problem to build super high speed amps. In that sense I consider Spectral rather sluggish.
 

Joachim Gerhard

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Here is a example of a high speed amp. It was build at Berlin university by some folks I know but they had to do some modifications to make it work in real.
 

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Joachim Gerhard

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They did not use the advertised PCB though , so can not say anything about Jans version.
 
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restorer-john

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I general in Germany we have a long tradition to build power amplifiers with a wide bandwidths. Early AudioLabor, Burmester and Omtec are examples. In England it is the other way around. Folks like Quad have claimed that there is no useful information over 20 kHz and there is even dirt out there that we do not want in our audio.

I'd say it was the Japanese who pushed the bandwidth of audio amplification in the 1970s. They developed the fast silicon and the DC-Daylight designs.

EU regulations have nobbled bandwidth- a huge proportion of 80s and 90s wide bandwidth Japanese products were fitted with filters on inputs and outputs to adhere to regulations in Europe but omitted everywhere else in the world due to performance reasons.
 

fosti

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..... Ncore and Purifi, highly praised here, have bandwidth limiting by nature to suppress the switching artifacts. .....
You think you know what you are talking about with 5o years of experience???? I'm not sure you are!
 

haraldo

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I have not decided what I like the best and I am unsure myself .....

I heard class D designs like Spectron Musician III and Mola Mola Kaluga presenting pure magic; I am wondering why Putzeys only do class d, he said in an interview that "ncore is really good despite being class D":rolleyes:

On the other hand, an "über the top" amp like Soulution 511 makes me completely forget that we are talking reproduced music, switching from any other amp to this one seem to bring me closer to the music; Whether this is the result of the ultra extreme bandwidth or it's a combination of that with many other extreme measures .... heck if I know :rolleyes:
Then if you want to soulution 511 to be fully balanced you need to mono-couple them and have two of them: we are certainly not talking pocket change with these kinds of products :eek:
 

fosti

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CD's are already bandlimited......another bandlimiting by class-d amplifiers do not add any more "artifacts" like J claims (which are no, you have to understand that!)!
 

haraldo

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CD's are already bandlimited......another bandlimiting by class-d amplifiers do not add any more "artifacts" (which are no, you have to understand that!) like J claims!

There is turntables and vinyl...
If I understand well.... This is not necessarily about artifacts above 20Khz, but phase shifts
 

fosti

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20kHz+ on Vinyl or bandmachines that add valuable tonal hearing ......of course!!! .......not!

EDIT: If you have watched the video of Monty: Bandmachines like a Studer can go as 13 bits deep in resolution with dither, that's DDD and no you come along with Vinyl......no, no, no....
 

haraldo

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what is the not .... or the no, you are referring to here?
 
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