DIY Purifi Amp builds

[March Audio]

Why make other people's life so difficult...
Subjective impression is allowed in this forum, as long as it is not pretend to be objective and accurate.
Amir does subjective review in his speaker test and it doesn't always align with the (incomplete) objective measurement.

No one is making anyone's life difficult. Jim proposed his experiment, and its more than just a comment on a subjective impression, and he was advised of the potential problems and given suggested solutions.

Subtle difference there. Amir is a trained listener who is acutely aware of the foibles of uncontrolled comparisons. Even then I take his speaker subjective comments with a very large pinch of salt. Listening sighted after seeing the measurements is not the way to do it.

 

[SIY]

Subtle difference there. Amir is a trained listener who is acutely aware of the foibles of uncontrolled comparisons. Even then I take his speaker subjective comments with a very large pinch of salt. Listening sighted after seeing the measurements is not the way to do it.

Ditto- when I publish speaker reviews, I am very careful to caveat my comments with the disclaimer that I did NOT do a proper controlled listening test.

Since beginning my reviewer gig, I haven't found accurate-measuring electronics where I thought I heard a difference, but if I ever do, be assured that will be verified (or falsified) by a real listening test.

And I've been hearing the claim that there's aspects to amp sound going beyond frequency response, clipping, and gross levels of distortion, but after 40 years of such claims and no-one ever managing to present evidence of this beyond repeated assertion, sneering, and figurative foot-stamping, I think it's pretty safe to say that if it measures better than established auditory thresholds, it will be transparent and thus not sound any different than any other good-measuring amp. This won't keep people from wasting time chasing this stuff with fundamentally flawed experiments, but still, it needs to be said.

 

[Dimitri]

A chef , a dietician , and a food critic went out to dinner ...
One of them ordered for all, one of them only had a drink but didn't eat, and one of them refused to pay their share of the bill ...

 

[JimM]

Let's see the name of this forum is DIY Purifi Build is it not ok. Thanks to JimB, Massimo, londonLad, and others here is my build.
Jan 7,2020 ordered parts post#183 - Jan 14 received chassis - Jan 18 finished chassis with hardware mounted and started checkout post #320 - Jan 26 Working 12 volt remote control with front panel switch and LED feed back, using off the shelf parts post #382 - Jan 27 block diagram for off the shelf parts post #389 - Feb 4 simplified wiring using bread board opto isolators for 12v remote control, front panel switch, and LED feed back, published schematic post #428. So within around 5 weeks built / assembled a finished amplifier. SIY where is your build maybe you would like to publish it on this forum, since it is about science. And that goes for all the other experts let's see your builds. Once again thanks to all the real contributes to this particular forum. March you could have answered a lot of questions we had but you did not and that's ok. Let's hear from the real contributors and builders and what the results of your efforts have been. I would think most of us that have built the Purifi amp have a amplifier and speakers before the build, the only real evaluation you can do is against a known standard and if you are like most people that will be the amplifier you currently have.
JimM

 

[SIY]

SIY where is your build

Sitting on top of my equipment rack. And it sounds identical to two other excellent amps I had in here before it, which is to say audibly transparent.

 

[JimB]

Let's see the name of this forum is DIY Purifi Build ...
JimM

I'm pleased that I could contribute to furthering people doing successful builds of these new Purifi based amps. But, personally, after all the preparations, I am waiting for my cases before finalizing my three builds...

As for listening tests, I'll just acknowledge that it is really hard to do well enough to draw 'objective' conclusions. That doesn't stop us from doing them. So, when someone seems willing and able to do one, it is a bit special, and I think we'd like to encourage going that extra mile to get results that others could use (sufficiently controlled).

 

[March Audio]

Once again thanks to all the real contributes to this particular forum. March you could have answered a lot of questions we had but you did not and that's ok. Let's hear from the real contributors and builders and what the results of your efforts have been.
JimM

I think you should perform a search on my contribution in the thread. Sorry that wasnt enough for you, but Im not sure its my responsibility to continually monitor the thread and spring into action answering all the questions you posed when they cropped up. Or to teach you electronic engineering.

 

[March Audio]

Let's see the name of this forum is DIY Purifi Build
JimM

Jim, you were the one who raised the subject of listening tests in this thread.

 

[JimM]

I surrender, once again thanks for all the contributors to the build it is a good amp. By
JimM

 

[kaka89]

I surrender, once again thanks for all the contributors to the build it is a good amp. By
JimM

Sorry to see you go.

I don't know why sharing of personal experience and subjective opinion is not permitted in this forum, this is silly.
What is the purpose of objective measurement if it doesn't translate to something personal. What is the meaning of this

 

[SIY]

I don't know why sharing of personal experience and subjective opinion is not permitted in this forum, this is silly.

Where did you get that silly idea? Was he banned? Posts removed? Door kicked down?

Nope.

But if you're on a science forum and you propose a fatally flawed experiment, then balk at criticism, it's on you, not the forum. Science means doing valid experiments, and that means (at the very least) basic controls.

 

[kaka89]

But if you're on a science forum and you propose a fatally flawed experiment, then balk at criticism, it's on you, not the forum. Science means doing valid experiments, and that means (at the very least) basic controls.

But nobody ever claim this to be a science experiments.
I know this is a science forum, but people also always express their personal preference in here as well. (eg wide vs narrow speaker dispersion)

What JimM wanted to post is no different from Amir's subjective speaker comments. Everyone read it should be with caution. JimM wasn't even trying to claim that one amp is better than the other...

 

[SIY]

I know this is a science forum...

Full stop right there.

 

[Thomas savage]

The more controls the more value , less controls or no controls and you have potentially misleading information. You may well be misleading yourself as well as others with your conclusions .

No one here should have a issue with someones subjective evaluation, unless it's being present as more than it is.

We are formed together by a respect for audio research and sound reason , let's keep that in mind.

Cheers

 

[BobPM]

Full stop right there.

This is the flip-side of the BS going on a the former Computer Audiophile forum. First, this is comments to a forum not some peer reviewed paper-- lighten up! All of us are adults capable of assigning appropriate weight to a comment on how a person perceives the sound of his equipment. And please speak for yourself, because I appreciate those opinions when they are properly qualified when made.

Before you attack my qualifications, I am a former geophysicist and spent years processing ultra low frequency sound waves to remove noise and tease out data on the composition of the earth's crust from the reflected sound waves. Not audio, but I have some sense of what is being done and how the scientific process works.

Please don't ruin this forum be imposing some purist nonsense and perceiving that what this forum is and what you are doing is more than it is.

 

[SIY]

This is the flip-side of the BS going on a the former Computer Audiophile forum. First, this is comments to a forum not some peer reviewed paper-- lighten up! All of us are adults capable of assigning appropriate weight to a comment on how a person perceives the sound of his equipment. And please speak for yourself, because I appreciate those opinions when they are properly qualified when made.

Before you attack my qualifications, I am a former geophysicist and spent years processing ultra low frequency sound waves to remove noise and tease out data on the composition of the earth's crust from the reflected sound waves. Not audio, but I have some sense of what is being done and how the scientific process works.

Please don't ruin this forum be imposing some purist nonsense and perceiving that what this forum is and what you are doing is more than it is.

Nothing purist, this is just basic controls to back up what could otherwise be extraordinary claims. Yes, it's more work, but that's how you achieve validity. There's lots of make-believe in the audio hobby world (most of which is strongly encouraged by the hucksters selling to them), and there's no reason that it shouldn't be called out for what it is.

Double-blind level matched comparisons between amplifiers are achievable by hobbyists, and it strikes me as odd that someone dropping thousands of dollars into it would balk at spend a couple hours setting up a good experiment before coming to some conclusions.

 

[mocenigo]

The more controls the more value , less controls or no controls and you have potentially misleading information. You may well be misleading yourself as well as others with your conclusions .

No one here should have a issue with someones subjective evaluation, unless it's being present as more than it is.

We are formed together by a respect for audio research and sound reason , let's keep that in mind.

The only problem here is the language used to convey what is an opinion. If a lot of care is put into matching, the experiment may not be FATALLY flawed, but have a higher level of indeterminacy as other, more precise settings. Sometimes discussions here are reduced to black-and-white, to a binary choice. Either the experiment is ok, or it is fatally flawed. This is not how science works, and that's why there are levels of precisions ("sigmas" in some fields) and ranges of errors. One cannot just claim that a 0.1Db mismatch makes a test complete invalid: I want to see how much this may introduce indeterminacy. Science is something more sophisticated than that, and that's why (apart from my tone) I stay by my past comment that also the "science" here is sometimes flawed (not to speak of the cult status attributed to the founder of the forum, which is most definitely against his own wish).

 

[Thomas savage]

The only problem here is the language used to convey what is an opinion. If a lot of care is put into matching, the experiment may not be FATALLY flawed, but have a higher level of indeterminacy as other, more precise settings. Sometimes discussions here are reduced to black-and-white, to a binary choice. Either the experiment is ok, or it is fatally flawed. This is not how science works, and that's why there are levels of precisions ("sigmas" in some fields) and ranges of errors. One cannot just claim that a 0.1Db mismatch makes a test complete invalid: I want to see how much this may introduce indeterminacy. Science is something more sophisticated than that, and that's why (apart from my tone) I stay by my past comment that also the "science" here is sometimes flawed (not to speak of the cult status attributed to the founder of the forum, which is most definitely against his own wish).

We don't really do any ' science ' here .

 

[Matias]

https://vacuumtubevalues.com/product/27564/

Figured I'd bite first since it was posted by someone else on here ... already got it in the mail!!! Being located in the USA makes it nice as there isn't any worry about customs fees or shipping delays. Perhaps one reason they can make it for such a great price is they don't have to add in overseas shipping? (I put together a NC502mp and the case from China took over a month to arrive due to the current situation)

The 'stock' buffers in this version are two separate NC500 OEM adaptors. It works/sounds as good as my other regular Hypex NC502MP amp with my Raal headphones/drives my Magnepans louder than I'd ever want. Honestly, I doubt you'd be able to tell the difference between the two amps ... Essentially the Purifi on paper is cleaner ... but the 502MP has more power ... so depending on what you're driving; one might be better than the other for your needs. The $879 price is great considering you don't have to put it together yourself!

Could you please post some pictures from the inside?

 

[mocenigo]

View attachment 57817

Definitely it has a lot of value, I cannot imagine this to be had at a better price. But:
- The placement of the boards is puzzling to say the least and
- As explained by Alan of @March Audio HERE and HERE the Hypex OEM board "has no bandwidth limitation. There are no feedback caps and it's wide open. This can cause unpredictable performance and make it susceptible to issues such as general environmental RF and that coming out of dacs." In other words, it is an evaluation board and unless modified it is not really suitable for a general purpose product. And for the price, I am not sure now they could have modified the input boards.

But for that ridiculous price you do get a lot of stuff: two Purifi boards, a Hypex power supply, and a case. One can still modify it and bring it to a better standard, with proper input buffers (for instance with @tomchr 's input boards).