Purifi Class D

[Allan F]

FWIW, the following is an excerpt from AF Digitale's review of the Rouge Audio Studio N8 stereo amplifier based on the new Purifi 1ET7040SA module:

 

Compared to the 1ET400A, this Purifi 1ET7040SA marks a big step forward, in addition to greater power, the sound seems to have acquired a soul: now it is richer and more harmonious.

[mocenigo]

19 minutes ago, Allan F said:

FWIW, the following is an excerpt from AF Digitale's review of the Rouge Audio Studio N8 stereo amplifier based on the new Purifi 1ET7040SA module:

 

Compared to the 1ET400A, this Purifi 1ET7040SA marks a big step forward, in addition to greater power, the sound seems to have acquired a soul: now it is richer and more harmonious.

AF Digitale usually writes just loads of cr*p, and this is no exception. If you look at their descriptions of digital technology, for instance, you will see a total lack of understanding of science and engineering.

 

The Purifi designers claim that the two modules will sound indistinguishable except if you need more power at low impedance; and that you will only hear a difference in that case.

[Allan F]

2 hours ago, mocenigo said:

The Purifi designers claim that the two modules will sound indistinguishable except if you need more power at low impedance; and that you will only hear a difference in that case.

 

For the general reasons stated by @barrowsin his earlier reply to my question regarding sound quality and the two modules, improved sound quality with the 1ETt7040SA may be an unintended and fortuitous benefit in certain systems.

[mocenigo]

5 hours ago, Allan F said:

 

For the general reasons stated by @barrowsin his earlier reply to my question regarding sound quality and the two modules, improved sound quality with the 1ETt7040SA may be an unintended and fortuitous benefit in certain systems.

Yes, but only when the impedance is really tough and/or you need a lot of power in the low frequencies. Which should almost never be the case, but some audiophiles still buy speakers needlessly difficult to drive…

 

The 1ET7040SA exists to satisfy the needs of users that otherwise would have to purchase one of those d’Agostino/Griphon/etc monsters that can pull out 1Kw at 2ohms and lower. And provide a differentiator between the DIY and OEM options.

 

And there is NOTHING unintended and fortuitous in the sonic benefits it may have in some circumstances. the ridiculous statement comes from the same place that causes audiophiles to believe that “an artistic approach” or “high quality capacitors and resistances” may make a difference, I.e. faith in snake oil, whereas audio reproduction is science and engineering and nothing else.
It the two modules are used with speakers they are meant to be driving comfortably, there will be no sound difference. If one uses speakers that the 1et7040sa will drive in its ideal operating conditions and the 1et400a will not, there will be a difference.

 

The folks at AF Digital, with their incompetence, are either victims of self-delusion, or price tag, or have exactly that type of speakers.

[Zauurx]

Here :

https://www.audio “science” review/forum/index.php?threads/say-hello-to-boxem-audio-arthur-series-hypex-and-purifi-based-power-amplifiers.16674/post-1276043

 

(and here : french)

http://forum-hifi.fr/thread-19292-post-605949.html#pid605949

 

 

[barrows]

7 hours ago, mocenigo said:

“high quality capacitors and resistances” may make a difference, I.e. faith in snake oil,

Umm, dude  you are wrong if you think all capacitors and resistors are the same.  Noise and distortion of different capacitors and resistors are both measurable and audible.  While I agree that there are some audiophile "beliefs" which are not based in reality, quality and performance differences between passive parts such as these are not debatable.  Perhaps how large those differences are could be debatable...

Just a single example: all resistors add noise to the circuit path they are used in, some resistors add less noise than others.  This noise adds up, considering how many resistors are in many audio circuits, and given contemporary low noise circuit designs resistor noise is a significant part of the noise at the output of components.  Susumu makes some of the very best low noise thin film resistors available, and their company touts the low noise characteristics of their resistors-they do not do this for "audiophile" reasons, as that market is tiny, they do so for industrial use applications, such high precision measurement and med-tech uses.  There is nothing crazy about this, some resistors are better than others.

[Jud]

39 minutes ago, barrows said:

Umm, dude  you are wrong if you think all capacitors and resistors are the same.  Noise and distortion of different capacitors and resistors are both measurable and audible.  While I agree that there are some audiophile "beliefs" which are not based in reality, quality and performance differences between passive parts such as these are not debatable.  Perhaps how large those differences are could be debatable...

Just a single example: all resistors add noise to the circuit path they are used in, some resistors add less noise than others.  This noise adds up, considering how many resistors are in many audio circuits, and given contemporary low noise circuit designs resistor noise is a significant part of the noise at the output of components.  Susumu makes some of the very best low noise thin film resistors available, and their company touts the low noise characteristics of their resistors-they do not do this for "audiophile" reasons, as that market is tiny, they do so for industrial use applications, such high precision measurement and med-tech uses.  There is nothing crazy about this, some resistors are better than others.

 

Back when I built my own DAC, I had the opportunity to try out different capacitors (same published specs) in each of the two different channels. Then I used high quality mono recordings (Pet Sounds) to see if there was any difference between right and left. I thought there plainly was.

 

This was not a blind test, so certainly fallible on that score, but it did have the advantage over the usual A/B testing that I could hear both channels/capacitors simultaneously and did not have to rely on memory. (The scientific consensus based on many experiments is that auditory memory lasts about 4 seconds.)

[PYP]

1 hour ago, Jud said:

 

Back when I built my own DAC, I had the opportunity to try out different capacitors (same published specs) in each of the two different channels. Then I used high quality mono recordings (Pet Sounds) to see if there was any difference between right and left. I thought there plainly was.

 

This was not a blind test, so certainly fallible on that score, but it did have the advantage over the usual A/B testing that I could hear both channels/capacitors simultaneously and did not have to rely on memory. (The scientific consensus based on many experiments is that auditory memory lasts about 4 seconds.)

And one would need to something similar with the two Purifi modules, one of which isn't available to DIYers.  So, there is no way to know how the two modules compare (subjectively).  

 

When Hypex started this way of distributing both DIY and OEM versions of the Bruno-designed modules, the companies that used the higher powered version also tended to use original input circuits, better casework (including better isolation of power supplies and modules), output connectors, power supplies (including original designs), etc.  Therefore, there wasn't a way to do an apples-to-apples comparison.  Does it matter?  Better implementation = better sound.   

 

Perhaps it is more important to celebrate the release of a truly formidable module that is available to DIYers at a very reasonable price.  

[mocenigo]

2 hours ago, barrows said:

Umm, dude  you are wrong if you think all capacitors and resistors are the same.  Noise and distortion of different capacitors and resistors are both measurable and audible.  While I agree that there are some audiophile "beliefs" which are not based in reality, quality and performance differences between passive parts such as these are not debatable.  Perhaps how large those differences are could be debatable...

 

I actually agree with you but for me manufacturing decent capacitors should be standard, yet there are several cheap ones which are just crap. So there would be "quality" and "crap" – not "high quality". For instance, not only what you say is correct, but capacitors may suffer from magnetostriction, pick up vibrations, have a filtering effect that differs from the ideal model in a significant way (creating the "bright" or "dark" capacitors, which is also of course nonsense since the effect would be the opposite if they are in series or in parallel with the signal...).  When they start speaking of "high quality" of these components I get immediately allergic. For me it is absolutely normal to buy well build ones, such as clarity cap. The differences with the "higher quality' ones is mostly in the shape of the deviations from the ideal model and I sincerely doubt that there are ideal capacitors. Another differentiator is longevity and stability, esp in a hot environment.

 

Similarly, I buy good Mundorf inductors because their foil-like windings and if there is a core, the quite one core, guarantee a working closed to the ideal one than many other products - so the simulations of, say, a crossover, with actual driver measurements included, will be closed to the real thing than with a smaller inductor, with a higher resistance, with less controlled flux.

 

But if somebody is trying to tell me that having silver or gold foil in a capacitor or inductor will make it "better", well, maybe different, and it would be fun to try an ABX test to see whether they can distinguish them...

 

 

2 hours ago, barrows said:

Just a single example: all resistors add noise to the circuit path they are used in, some resistors add less noise than others.  This noise adds up, considering how many resistors are in many audio circuits, and given contemporary low noise circuit designs resistor noise is a significant part of the noise at the output of components.  Susumu makes some of the very best low noise thin film resistors available, and their company touts the low noise characteristics of their resistors-they do not do this for "audiophile" reasons, as that market is tiny, they do so for industrial use applications, such high precision measurement and med-tech uses.  There is nothing crazy about this, some resistors are better than others.

 

True, some resistors have also a non-negligible inductance. That's why I buy good MOX resistors, and not wirewound. 

 

Maybe we are so negatively spoiled by crappy and cheap components that what I consider decent engineering, a normal prerequisite, is now a luxury.

 

 

[Allan F]

10 hours ago, mocenigo said:

And there is NOTHING unintended and fortuitous in the sonic benefits it may have in some circumstances. the ridiculous statement comes from the same place that causes audiophiles to believe that “an artistic approach” or “high quality capacitors and resistances” may make a difference, I.e. faith in snake oil, whereas audio reproduction is science and engineering and nothing else.

 

I don't know if you don't know the meaning of unintended or fortuitous, but your statement doesn't make any sense in the context of this discussion.

[barrows]

15 minutes ago, mocenigo said:

Maybe we are so negatively spoiled by crappy and cheap components that what I consider decent engineering, a normal prerequisite, is now a luxury.

This could be the case.  A huge part of the training of engineers is that they are always trained to deliver a design which will "work" at the lowest possible cost.  While given design may "work", this approach might not be the best when sound quality is a design goal.  For example, the sound quality of a resistor used in a control circuit for a washing machine is of no consequence, and cost is likely the most important factor besides longevity/reliability.

In my work in audio, when hiring engineers for design help, it has often been hard to get those engineers to understand that cost may not be so important, and that it is OK to spec a resistor which might be 2x or even 4x the cost of a lessor part.

[PYP]

9 minutes ago, barrows said:

This could be the case.  A huge part of the training of engineers is that they are always trained to deliver a design which will "work" at the lowest possible cost.  While given design may "work", this approach might not be the best when sound quality is a design goal.  For example, the sound quality of a resistor used in a control circuit for a washing machine is of no consequence, and cost is likely the most important factor besides longevity/reliability.

In my work in audio, when hiring engineers for design help, it has often been hard to get those engineers to understand that cost may not be so important, and that it is OK to spec a resistor which might be 2x or even 4x the cost of a lessor part.

and are parts then tested against a standard?  It seems that to get the sound the designer wants electronic (and non-electronic) parts need to be tested and matched for consistency.   

[mocenigo]

34 minutes ago, Allan F said:

 

I don't know if you don't know the meaning of unintended or fortuitous, but your statement doesn't make any sense in the context of this discussion.

 

I see you have edited it. So let us see from the dictionary

 

unintended | ˌʌnɪnˈtɛndɪd | adjective Not planned or meant: the unintended consequences of people's actions.

fortuitous | fɔːˈtjuːɪtəs | adjective happening by chance rather than intention: the similarity between the paintings may not be simply fortuitous. • happening by a lucky chance; fortunate: the ball went into the goal by a fortuitous ricochet.

 

I can confirm that I intended to use these works exactly as they are defined in the dictionary.

Also, the statement makes sense.

 

And, yes, I see that you were mistaken by inferring that I claimed that resistors and capacitors make no difference. Ouch ouch ouch! :-)

 

 

[mocenigo]

23 minutes ago, barrows said:

This could be the case.  A huge part of the training of engineers is that they are always trained to deliver a design which will "work" at the lowest possible cost.  While given design may "work", this approach might not be the best when sound quality is a design goal.  For example, the sound quality of a resistor used in a control circuit for a washing machine is of no consequence, and cost is likely the most important factor besides longevity/reliability.

In my work in audio, when hiring engineers for design help, it has often been hard to get those engineers to understand that cost may not be so important, and that it is OK to spec a resistor which might be 2x or even 4x the cost of a lessor part.

 

Most of engineering today is "do as cheaply as possible and it is explodes, let it explode after the warranty has expired".

[Allan F]

41 minutes ago, mocenigo said:

I can confirm that I intended to use these works exactly as they are defined in the dictionary.

Also, the statement makes sense.

 

Congratulations. But your statement still doesn't make any sense. 🙂

Over and out.

[Jud]

Sorry for helping to continue this tangent about parts. We were discussing possible sound comparisons between Purifi modules. Miska explained this may well depend on the complex impedance of one's speakers. Something else I found interesting along analogous lines is that in the video interview with Bruno Putzeys that Duck Toller posted, Putzeys says a TI op amp with higher power and higher distortion specs actually works better than the one with a lower distortion spec he put in the Purifi input buffer. He gives a brief explanation as to why.

[barrows]

3 hours ago, Jud said:

Sorry for helping to continue this tangent about parts. We were discussing possible sound comparisons between Purifi modules. Miska explained this may well depend on the complex impedance of one's speakers. Something else I found interesting along analogous lines is that in the video interview with Bruno Putzeys that Duck Toller posted, Putzeys says a TI op amp with higher power and higher distortion specs actually works better than the one with a lower distortion spec he put in the Purifi input buffer. He gives a brief explanation as to why.

Thanks @Judfor pointing this out, I had not listened to this interview.  I happened to have a pair of OPA 1656 left over from a  previous project, and just swapped out the 1612s on my Purifi build with the 1656s (on the Purifi EVAL 1)...  Warming up in the system now...  the 1656 has 2x the current of the 1612, and I always suspected that the current delivery of the 1612 was a bit on the low side for this purpose.  Very cold amp right now, but sounds a bit better with the 1656s...  I'll let it run overnight to warm up and listen more tomorrow.

[mocenigo]

42 minutes ago, barrows said:

Thanks @Judfor pointing this out, I had not listened to this interview.  I happened to have a pair of OPA 1656 left over from a  previous project, and just swapped out the 1612s on my Purifi build with the 1656s (on the Purifi EVAL 1)...  Warming up in the system now...  the 1656 has 2x the current of the 1612, and I always suspected that the current delivery of the 1612 was a bit on the low side for this purpose.  Very cold amp right now, but sounds a bit better with the 1656s...  I'll let it run overnight to warm up and listen more tomorrow.

 

Ah, I use Neurochrome's Universal Buffer. No shortage of current with that one.

[mocenigo]

4 hours ago, Allan F said:

 

Congratulations. But your statement still doesn't make any sense. 🙂

Over and out.

 

It does. A lot of audiophiles drink the cool aid of snake oil vendors that speak of "hand made cables", "after many experiments with different types of conducting material and dielectric, all validated with listening sessions" and so on, as if things in audio happened "just" because untrained people try out many combinations. And they believe they can be as good because they try a lot of stuff.  Whereas, even if many here poke fun of audio "science" review, and a few guys there even deserve that, well, audio reproduction IS science and engineering, and nothing else. Building better and better slings for marbles as a hobby does not make one an experimental physicist at a synchrotron, but in the audiophile world this seems to be the common belief.

[Allan F]

1 hour ago, mocenigo said:

 

It does. A lot of audiophiles drink the cool aid of snake oil vendors that speak of "hand made cables", "after many experiments with different types of conducting material and dielectric, all validated with listening sessions" and so on, as if things in audio happened "just" because untrained people try out many combinations. And they believe they can be as good because they try a lot of stuff.  Whereas, even if many here poke fun of audio "science" review, and a few guys there even deserve that, well, audio reproduction IS science and engineering, and nothing else. Building better and better slings for marbles as a hobby does not make one an experimental physicist at a synchrotron, but in the audiophile world this seems to be the common belief.

 

The above has absolutely no application or relevance to what I wrote about an "unintended and fortuitous benefit", in which context your reply made no sense. Bye!

[davide256]

If the bass driver(s) can push the lower limits of the bass octave, more power improves the ease of bass production

[Kimo]

On 11/14/2022 at 6:34 PM, Allan F said:

 

The above has absolutely no application or relevance to what I wrote about an "unintended and fortuitous benefit", in which context your reply made no sense. Bye!

 

Must you continue to prove your worthlessness here over and over?  Maybe, on the 5000th post you will add some value?

[PYP]

1 hour ago, Kimo said:

 

Must you continue to prove your worthlessness here over and over?  Maybe, on the 5000th post you will add some value?

Time to Purifi the thread.  Can we move on?

[Kimo]

11 minutes ago, PYP said:

Time to Purifi the thread.  Can we move on?

Of course.  The rest of you are doing great.

[Jud]

On 11/11/2022 at 10:19 AM, DuckToller said:

recent YT with Bruno ...
Thanks for the link at FB Lars Risbo!

 

 

Grateful thanks for this.  During the interview, as noted previously in the thread, Bruno says the TI OPA 1656 op amp will sound better than the TI OPA 1612 op amp he includes with his eval board (and that ships with various Purifi-based amps, including my Apollon).  Barrows tried the OPA 1656 and told me he liked it, so I got hold of a couple (at least for the Apollon, you want the DIP8 modules - readily available on eBay in the US for less than $20 the pair; don't know about availability in other countries).  Surprise, I think Bruno was right; I feel that I like the sound better.  Subjective impression (so to be taken with a grain of salt) is richer, more reverberant, more musical, sweeter, without being overly warm or less accurate.