Review and Measurements of Purifi 1ET400A Amplifier

[boXem]

I did not say it was easy, nor did the article. I do not understand the comment at all, sorry.

Neither you nor the article said it's easy. I intended to express that the article being an easy reading, one could conclude that feedback is easy, which is not the case. Sorry for the misunderstanding.

 

[Julf]

From pure engineering standpoint, too much feedback leads to a lot of problems for the engineer.
Bruno's article is really nice to read, but one should not conclude of it that feedback is easy. It's one big part of the control theory and it requests some background in maths.

Absolutely - but "too much" feedback is still not bad in any way, as long as one knows how to deal with the constraints.

 

[HiFiSoundFarts]

You are confused. I asked if a blind test had been done. That is all. Now you're adding your own spin.

This is the reason why a link to the information is needed. Your recollections of things recorded in this thread appear faulty, so one must ask if your recollections on other issues are close to being accurate... and you've yet to provide proof of anything.

Perhaps you need time to clarify your thoughts, sort through your data, and present this data in a form other than your personal impressions?

You really need to do some research about what evidence does mean.

Again, about substantial proof.

Commercial interviews may hardly be considered as scientific proof. Whatever how skilled the manufacturers are supposed to be (both Benchmark or Chord are, BTW). When the number of people liking a product could be considered as a proof of performance? What about Audio-GD, Schiit or most AVRs? Do we have to talk about audiophile cable industry?...


ASR is a place full of data and a lot of knowledgeable people to learn from. More than any other audio forum I've been. Insulting the entire forum because you're unable to source your claim (your source, which remains unquoted post after post) is not a good way to start your journey here.

I did not insult the forum I am saying to you that a place that calls itself a science forum should welcome reasonable, logical discussion instead of immediately shutting down a discussion because it is not in line with the fanatically religious belief systems that are so deeply held on this forum. On this forum, you either believe in the forum majority doctrine or you are a heretic.

 

[HiFiSoundFarts]

You really need to do some research about what evidence does mean.

Again, about substantial proof.

Commercial interviews may hardly be considered as scientific proof. Whatever how skilled the manufacturers are supposed to be (both Benchmark or Chord are, BTW). When the number of people liking a product could be considered as a proof of performance? What about Audio-GD, Schiit or most AVRs? Do we have to talk about audiophile cable industry?...


ASR is a place full of data and a lot of knowledgeable people to learn from. More than any other audio forum I've been. Insulting the entire forum because you're unable to source your claim (your source, which remains unquoted post after post) is not a good way to start your journey here.

You have people that have systems for years and they get to know their system intimately. Then they upgrade their amplifier and they notice a substantial improvement. You do not think this is a much better proof of design than extremely limited exposure to sound clips of which are so similar as to be impossible to remember/retain any slight minutia long enough to contrast and compare?

Again, how do you know for sure that double blind test are only measuring a human beings limited ability to remember or retain auditory information?
Memory is notoriously fallible so with such short duration, double blind test, how can anyone possibly notice a difference in hardware with the same accuracy as a person that has listened and learned their system for years.

 

[Julf]

On this forum, you either believe in the forum majority doctrine or you are a heretic.

Indeed. That majority doctrine is "verified evidence".

 

[Julf]

You have people that have systems for years and they get to know their system intimately. Then they upgrade their amplifier and they notice a substantial improvement. You do not think this is a much better proof of design than extremely limited exposure to sound clips of which are so similar as to be impossible to remember/retain any slight minutia long enough to contrast and compare?

No. Please study ITU BS.1116: Methods for the subjective assessment of small impairments in audio systems

Again, how do you know for sure that double blind test are only measuring a human beings limited ability to remember or retain auditory information?
Memory is notoriously fallible so with such short duration, double blind test, how can anyone possibly notice a difference in hardware with the same accuracy as a person that has listened and learned their system for years.

Human memory is indeed fallible, that is why tests can't rely on memory, but have to be designed to allow instantaneous switching back and forth. Remembering how a system used to sound doesn't really work.

 

[HiFiSoundFarts]

Indeed. That majority doctrine is "verified evidence".

You would not offer a reasonable argument against my questions that are logical and reasonable that refute this forum majority doctrine which shows that you consider your forum majority doctrine to be accepted on faith and not science. Hence the comment about why this forum should be called Audio Faith Review.

Instaneous switching still does not address the limited amount of time of exposure to the sound which prevents learning the full character of the hardware to an extent to be able to compare minute details in the sound. How do you know if this type of test is just measuring the brain's limits of processing ability and/or ability to learn? In other words, maybe the sound differences are perceptible, yet the brain has limits to how much that can be fully processed and retained within a given time frame? The brain automatically filters out a majority of the sensory information that is present so as to not overwhelm our ability to consciously direct our focus of thought. So these test could still just be measuring the brains ability to filter out auditory perceptual information.

 

[Julf]

You have not and will not offer a reasonable argument against my questions that are logical and reasonable that refute this forum majority doctrine which shows that you consider your forum majority doctrine to be accepted on faith and not science. Hence the comment about why this forum should be called Audio Faith Review.

Can you please remind me what your actual questions are?

 

[Biblob]

Has there been a price release or indication for this kit?

 

[JanRSmit]

I

The point concern me is feedback correction could affect the original signal ?

It does, it is the principale of negatieve feedback.

 

[ahofer]

”Instaneous switching still does not address the limited amount of time of exposure to the sound which prevents learning the full character of the hardware to an extent to be able to compare minute details in the sound. “

This is also wrong. There have been many, many blind tests where the subjects were allowed to take as long as they like. Look at the thread I started called “catalogue of blind tests”. None of them have demonstrated the controlled audibility of amplifiers, cables, etc.

I suggest you spend some time with the evidence. Start with the Head-Fi compendium of blind tests. It is staggering how little evidence there is for these types of golden ear claims. Staggering. That is why people are reacting to you with disbelief.

https://www.head-fi.org/threads/testing-audiophile-claims-and-myths.486598/

 

[GrimSurfer]

I suggest you spend some time with the evidence. Start with the Head-Fi compendium of blind tests. It is staggering how little evidence there is for these types of golden ear claims. Staggering. That is why people are reacting to you with disbelief.

https://www.head-fi.org/threads/testing-audiophile-claims-and-myths.486598/

I second @ahofer's suggestion. All in favor?

 

[g29]

Last time I spoke to Purify full production was going to in October

Is it October yet ???

 

[elberoth]

I'm getting the amp on Monday.

 

[ti33er]

Hey Elbroth, do you have an nc400 to compare it with, out of interest?

 

[elberoth]

Hey Elbroth, do you have an nc400 to compare it with, out of interest?

No, but I have the latest Nord based on NC500, with same input buffers (rev D). The only difference is the Opamps - SI in the NC500 based one and Sparkos Labs in the Purifi based one.

 

[ti33er]

Oh okay thanks ...that will be very hard to compare them really - need the Bruno colourless Buffer!!!

 

[georgehifi]

@amirm
Hi, my first post, by any chance do you have a 10khz phase shift (degrees) measurement at the output, without the use of any A.P. aux hf filtering involved?

Rusty Shackleford said:
What does the amp’s square wave look like?
amirmI am not sure what bandwidth JA uses at stereophile. but there is an AES-17 filter in addition:
Also do you have a shot of this 10k square wave without the A.P. hf filter attached?


Cheers George

 

[March Audio]

@amirm
Hi, my first post, by any chance do you have a 10khz phase shift (degrees) measurement at the output, without the use of any A.P. aux hf filtering involved?

Rusty Shackleford said:
What does the amp’s square wave look like?
amirmI am not sure what bandwidth JA uses at stereophile. but there is an AES-17 filter in addition:
Also do you have a shot of this 10k square wave without the A.P. hf filter attached?


Cheers George

For what purpose George? As I asked you in the other forum, what are you hoping to learn?

What is your concern about the AES filter?

BTW the frequency response will give you a clue about the phase shift at 10kHz.

This is the 10kHz square wave with AES filter. Without it you would see the 500 kHz switching frequency riding on top. However below is the correct representation of the waveform in real use because the switching frequency is filtered out and not reproduced by the speaker.

You were shown this information in the other forum. Are you expecting a different response here?

 

[georgehifi]

Excuse me, don't know why your answering, I asked @amirm , who's doing the measuring on this, not you.

What you posted up doesn't represent what I asked him for at all, just confuses it.

And I like to see what's coming out of the output of an amp, with and without the AP filter masking it.