Review and Measurements of Purifi 1ET400A Amplifier

[Audiocrusader]

Why is it that the folks that are over 70 always claim that they can hear higher frequencies than healthy 18 yr olds? I'd be shocked if half of them could hear 10khz let alone over 100khz! At which point should we decide to just throw in the towel and admit we can't hear shit anyways? And perhaps take up a hobby where your remaining functional senses could be still put to good use.

 

[Joachim Herbert]

Why is it that the folks that are over 70 always claim that they can hear higher frequencies than healthy 18 yr olds?

In my early 20s I was the proud owner of an Accuphase T-101 Tuner that was quite capable but produced an annoying high pitched sound. The dealer disputed the existence of that very noise, as did the german distributer that checked the unit.

Years later I found it was the stereo pilot tone these old men were not able to detect and which was not filtered appropriately.

 

[Audiocrusader]

In my early 20s I was the proud owner of an Accuphase T-101 Tuner that was quite capable but produced an annoying high pitched sound. The dealer disputed the existence of that very noise, as did the german distributer that checked the unit.

Years later I found it was the stereo pilot tone these old men were not able to detect and which was not filtered appropriately.

Let's just damn well admit it. High end audio is a young mans game. If you're over 50, just damn well listen to your smartphone DAC through a $200 class D amp and call it a day. Or whatever old relic you can find that will satisfy your nostalgia.

 

[March Audio]

Thanks amirm, requests 1: 2: and 3" from here, if you have them saved as screen shots.
https://www.audiosciencereview.com/...-of-purifi-1et400a-amplifier.7984/post-237856

Without A.P.'s passive low-pass filter.
As the output (without AP filtering) to me has a direct relationship to the amount of residual switching frequency noise seen on the 10k square wave, and also a direct relationship to the amount of shift down into the audio band if you've graphed that, and gives an idea where the amps output filter is set also.
These are hidden when the A.P.'s passive low-pass filter is used, I like to see it warts and all.


Don't know why it caused such bristling from some. Stereophile show both with and without A.P.'s AUX-0025 passive low-pass filter.



View attachment 34901

And the graph of phase shift figures, from this module.
View attachment 34902


Cheers George

George, you have dragged your fundamental lack of understanding from one forum into another. All this has been discussed at length with you previously but you choose to disregard it.

You have said above you think someone is lying about the filter response. This isn't the case. It is just that you don't want to beleive the information.

It should be noted that multiple posters on the other forum, and this one, have noted you have an anti class d agenda.

The 500khz switching signal you will see on the 10kHz waveform does not tell you anything about the in band phase shift.

 

[Audiocrusader]

George, you have dragged your fundamental lack of understanding from one forum into another. All this has been discussed at length with you but you choose to disregard it.

You have said above you think someone is lying about the filter response. This isn't the case. It is just that you don't want to beleive it.

It should be noted that posters on the other forum and this one have noted you have an anti class d agenda.

Let me guess, over 70? Explains everything. Let's give the guy a break. The forums is all he has. He can't hear anymore.

 

[ahofer]

(G Walks into room where people are talking energetically amongst themselves, stares at everyone meaningfully, grabs a megaphone)

“Amir, run these extra tests that I deem critical”

Rest of room, knowing amp has long since been sent back:
“Why, we don’t think they are particularly useful”

(G: Into megaphone) “Because! Now everyone shut up, I’m taking over this room and speaking only to Amir. Do not address me.

Everyone else: “hey, bugger off. So what are you on about?”

G: “DO NOT ADDRESS ME!”

Everyone else: “ who the F are you? Oh wait, we know you from your haughty and dogmatic behavior elsewhere. ”

G: “you are all so defensive and hostile-Ignore!”

Charmer.

 

[ahofer]

Let's just damn well admit it. High end audio is a young mans game. If you're over 50, just damn well listen to your smartphone DAC through a $200 class D amp and call it a day. Or whatever old relic you can find that will satisfy your nostalgia.

Hey, I resemble that remark.

And I’m only responding because it’s 3am and I can’t sleep.

 

[Audiocrusader]

Hey, I resemble that remark.

And I’m only responding because it’s 3am and I can’t sleep.

I don't get it. It seems to be firmly established that pretty much any piece of audio gear with a SINAD over 100 is beyond the threshold of audibility. And that's with the ears of a healthy young specimen. "If this is the case why do we always have a circle jerk when we see a SINAD higher than this point?? Shouldn't we only care about the cheapest possible gear we can find between 95-100 SINAD, and ignore all the rest? Unless of course the average age of this forum has better hearing than a healthy 18 yr old with perfect hearing. Wouldn't this be equivalent to putting 100+ octane fuel in a tired old 1998 Dodge Neon with 300000 miles on it?

 

[georgehifi]

The 1 Khz spectrum in the review is without the filter:

This is what I'm getting at amirm, you posted up this 10khz square wave shot of the Purifi.

But this is using the AP LP filter and does not represent what is actually coming out of the speaker terminals, this is what I would prefer to see, shots of with and without the AP LP filter in play, so one can get an idea of what really coming out of the speaker terminals Stereophile do it below, can it be done here??? Cheers George

 

[maty]

Making the measurement, when possible, ends the discussion.

 

[Joachim Herbert]

Wouldn't this be equivalent to putting 100+ octane fuel in a 1998 Dodge Neon?

No, it is more like driving a Porsche in the US of A.

 

[Audiocrusader]

No, it is more like driving a Porsche in the US of A.

Now that's a euphemism if I've ever heard one. Personally I'd much rather drive a Porsche at any age than stare at a piece of audio gear I've over paid for and can't hear anyways. And likely has the effect of scaring chicks away rather than attracting them like the Porsche would.

 

[Audiocrusader]

Making the measurement, when possible, ends the discussion.

Another man with ears as golden as can get. And absolutely no experience with any class D amps in his personal system. Yet acts as though he's the absolute authority on class d across any forum on the internet that whispers the word "class D" Thank god for the internet!

 

[March Audio]

This is what I'm getting at amirm, you posted up this 10khz square wave shot of the Purifi.
View attachment 34908
But this is using the AP LP filter and does not represent what is actually coming out of the speaker terminals, this is what I would prefer to see, shots of with and without the AP LP filter in play, so one can get an idea of what really coming out of the speaker terminals Stereophile do it below, can it be done here??? Cheers George

View attachment 34909

George you still haven't grasped that the 500kHz switching frequency *IS* filtered out by the speaker.

The signal *IS* as the filtered plot shows.

The switching signal is *NOT* coming out of the speaker.

Amir has already stated he doesn't have those measurements, however I can tell you they will look very similar to the Stereophile above.

 

[Audiocrusader]

George you still haven't grasped that the 500kHz switching frequency is filtered out by the speaker.

It is NOT coming out of the speaker.

So you're saying that if the speaker could play the 500khz signal, his 70+ year old ears would be able to hear it? I'd pay $500 to watch a video interview of him proving he could hear a 10khz test tone. Let alone 500khz. The facts of the matter is if any noise the amp produces above the audible range, doesn't fold back 2nd order effects into the audible range, they don't matter. The only reason we even need to measure above 50khz for audio reasons is to see if there's ultrasonic noise that is causing 2nd order noise in the audible band. But if there isn't any audible noise in the audible band it doesn't matter anyways!

 

[g29]

Now that's a euphemism if I've ever heard one. Personally I'd much rather drive a Porsche at any age than stare at a piece of audio gear I've over paid for and can't hear anyways. And likely has the effect of scaring chicks away rather than attracting them like the Porsche would.

California Confucius say, "The only chicks that go after men in Porsches are not after the men, but their wallet$.".

 

[Audiocrusader]

California Confucius say, "The only chicks that go after men in Porsches are not after the men, but their wallet$.".

I'd rather have a chick go after my wallet than no chick go after me at all. At least a smart man might be able to get a few quick shags in. As long as you wrap it up, no harm done. Something that your new Matrix DAC may fail to achieve by texting them the SINAD number.

 

[maty]

Another man with ears as golden as can get. And absolutely no experience with any class D amps in his personal system. Yet acts as though he's the absolute authority on class d across any forum on the internet that whispers the word "class D" Thank god for the internet!

Ignorance is very daring.

The measurement is made and the effectiveness of the filter at the output of the amplification module and discussion end. Class D deficiencies are others. Now we are facing new designs that have surely eliminated or minimized some of those usual or all of the class D deficiencies. Hence my interest in them and not in the old implementations!

 

[Audiocrusader]

Ignorance is very daring.

The measurement is made and the effectiveness of the filter at the output of the amplification module and discussion end. Class D deficiencies are others.

So what experience have you achieved through personal in home listening experience, or hands on measurements of class D amps, to give you the confidence to voice your opinion on the matter?

 

[maty]

Bad, as is evident. Not in my system, thanks God. Nor in these systems and others class AB I was able to differentiate between MP3 320 kbps (LAME) and FLAC 16/44, indicative of its limitations or bottlenecks.

I assumed that the same requirements in traditional amplification would also be considered with class D. Well, it turns out that it has not been so, hence my surprise and anger with the new Edge design in Icepower 1200AS2 (the other IP modules use 2004 technology).