Review and Measurements of Purifi 1ET400A Amplifier

[SIY]

Well they do not matter if you can't hear the differences.

Looking forward to your ears-only demonstration. Until then, these claims have all the evidentiary support of alien abductions with anal probing.

 

[rdenney]

If both speakers are wired out of phase, it shouldn’t matter. If the relative phase between the speakers is different (ie, one wired in phase, one wired out of phase) then it will matter big time.

Too dry? I am sometimes accused of humor that people don't catch.

More seriously, what I read is either 1.) an implementation error, 2.) a defective example, or 3.) the poster's imagination. As written, I'm going with 3 as the likeliest explanation (which I would go with even if I was the one doing the listening), but discounting that, the fickle finger of fate points to 1.

First, I would make sure that the amp is actually playing in stereo. (No, that was not dry humor.)

Rick "who owns neither a Purifi nor an Accuphase, and will now bow out" Denney

 

[roffe]

I got to hear a Purifi 1ET400A based amp today in a very good system.
It is almost really good but let down by having quite poor imaging -especially poor centre fill and image depth so it sounds very 2D .I was really surprised it sounded like that.The Accuphase amplifier in the same system had fantastic image depth /projection and height.We tried with and without active preamps and that did not make any difference.
Perhaps I need to recalibrate my expectations to fit in with modern amplifier technology ?I always used to believe that the whole point of stereo reproduction was imaging.

I replaced my beloved Accuphase with a NAD C298 and I'm never going back.

 

[jtgofish]

Too dry? I am sometimes accused of humor that people don't catch.

More seriously, what I read is either 1.) an implementation error, 2.) a defective example, or 3.) the poster's imagination. As written, I'm going with 3 as the likeliest explanation (which I would go with even if I was the one doing the listening), but discounting that, the fickle finger of fate points to 1.

First, I would make sure that the amp is actually playing in stereo. (No, that was not dry humor.)

Rick "who owns neither a Purifi nor an Accuphase, and will now bow out" Denney

Yes the not in stereo mode thing needs further investigation.It does sound a bit like that but I did not think to test it with a recording in which there are obvious different sounds on each channel.Voices do seem to sound like they are coming equally from each speaker on recordings tha normally have them front and centre.

 

[restorer-john]

I always used to believe that the whole point of stereo reproduction was imaging.

Absolutely correct. Imaging is the entire reason for stereo. But, what, specifically, was it about the Purifi vs the Accuphase where the imaging fell down?

 

[SIY]

Absolutely correct. Imaging is the entire reason for stereo. But, what, specifically, was it about the Purifi vs the Accuphase where the imaging fell down?

Seeing it.

 

[restorer-john]

Seeing it.

You are trolling. As in, the actual, real definition.

Dragging a fake attractant through the water, hoping some big fish, stupid enough to swallow the bait, will take it and run. You can do better.

 

[Phorize]

You are trolling. As in, the actual, real definition.

Dragging a fake attractant through the water, hoping some big fish, stupid enough to swallow the bait, will take it and run. You can do better.

All other factors being equal, and ruling out some hidden property that doesn’t show up in measurements, it seems likely that expectation bias is the culprit. That isn’t a criticism, there isn’t a human being alive that isn’t beholden to the limitations of their own personal computational infrastructure.

 

[restorer-john]

All other factors being equal, and ruling out some hidden property that doesn’t show up in measurements, it seems likely that expectation bias is the culprit. That isn’t a criticism, there isn’t a human being alive that isn’t beholden to the limitations of their own personal computational infrastructure.

Including the humans making the polar opposite claims, with little or no evidence of a compelling nature themselves. It works both ways- consider that.

 

[Phorize]

All other factors being equal, and ruling out some hidden property that doesn’t show up in measurements, it seems likely that expectation bias is the culprit. That isn’t a criticism, there isn’t a human being alive that isn’t beholden to the limitations of their own personal computational infrastructure.

Of course a properly controlled blind test is the best way to establish if a difference is really being heard at all. Until it is positively established that a difference is actual being heard there doesn’t seem to be a reason to look for other root causes.

 

[Phorize]

Including the humans making the polar opposite claims, with little or no evidence of a compelling nature themselves. It works both ways- consider that.

Absolutely agree.

 

[restorer-john]

Of course a properly controlled blind test is the best way to establish if a difference is really being heard at all. Until it is positively established that a difference is actual being heard there doesn’t seem to be a reason to look for other root causes.

I have probably 20 or more amplifiers here, in my listening room/lab. I can go get another 50 or more from my storeroom of various vintages and pedigrees. I can pop down to Dad's place and grab maybe 30 or 40 more. They all test differently. Some sound identical to one another, some don't.

My Technics comparator can be level matched, can switch multiple amplifiers, speakers and sources instantly, at any power level. It sorts the sheep from the goats...

 

[Phorize]

I have probably 20 or more amplifiers here, in my listening room/lab. I can go get another 50 or more from my storeroom of various vintages and pedigrees. I can pop down to Dad's place and grab maybe 30 or 40 more. They all test differently. Some sound identical to one another, some don't.

My Technics comparator can be level matched, can switch multiple amplifiers, speakers and sources instantly, at any power level. It sorts the sheep from the goats...

Not sure how to respond really. It obviously isn't debatable that some amplifiers can be audibly different to others, but surely we agree that if they are audibly different, then that difference will be visible in the measured performance of the amp?

 

[Matias]

Output impedance reflects directly into the frequency response.
http://archimago.blogspot.com/2021/08/summer-musings-no-not-all-amplifiers.html

 

[Rja4000]

Output impedance reflects directly into the frequency response.
http://archimago.blogspot.com/2021/08/summer-musings-no-not-all-amplifiers.html

I was about to post the same.
It's an interesting topic.
And matches my experience as well: there are actual differences in how amps sound (at least for low end amps)
That translates mostly in frequency response.
I still wonder how some kind of dynamic compression (or extension) could also be there and remain hidden from typical measurements.
That for sure could make an audible difference too.

 

[DonH56]

https://www.audiosciencereview.com/...amping-factor-and-speakers.23968/#post-807327

High output impedance can also increase distortion. Audibly? Not my department...

 

[phoenixdogfan]

As for amplifiers, not all amplifiers sound alike, but all amplifiers that are engineered to meet certain conditions certainly do. As Peter Aczel put it:

"Any amplifier, regardless of topology, can be treated as a “black box” for the purpose of listening comparisons. If amplifiers A and B both have flat frequency response, low noise floor, reasonably low distortion, high input impedance, low output impedance, and are not clipped, they will be indistinguishable in sound at matched levels no matter what’s inside them. Of course, some of the new “alphabet soup” topologies do not necessarily satisfy those conditions. "

 

[restorer-john]

As for amplifiers, not all amplifiers sound alike, but all amplifiers that are engineered to meet certain conditions certainly do. As Peter Aczel put it:

"Any amplifier, regardless of topology, can be treated as a “black box” for the purpose of listening comparisons. If amplifiers A and B both have flat frequency response, low noise floor, reasonably low distortion, high input impedance, low output impedance, and are not clipped, they will be indistinguishable in sound at matched levels no matter what’s inside them. Of course, some of the new “alphabet soup” topologies do not necessarily satisfy those conditions. "

The Aczel quote is tired. There's no substance to it as there are no qualifications, just vagaries.

Maybe if some actual meaureable limit lines were drawn in the sand it'd be worth holding up as a remotely useful statement.

It's just as self serving as the "you can't hear a difference if your system isn't resolving enough".

 

[jtgofish]

https://www.audiosciencereview.com/...amping-factor-and-speakers.23968/#post-807327

High output impedance can also increase distortion. Audibly? Not my department...

That is mostly in speakers that are not designed well.Speakers should have a flat impedance curve of around 8 ohms.Whereas many have a highly uneven impedance curve which dips down to 2 or 3 ohms [ typical difficult load].Then you need an amplifier with high damping factor/low output impedance/high negative feedback to drive them properly.Which is arguably two wrongs trying to make a right.

 

[rcstevensonaz]

As for amplifiers, not all amplifiers sound alike, but all amplifiers that are engineered to meet certain conditions certainly do. As Peter Aczel put it:

"Any amplifier, regardless of topology, can be treated as a “black box” for the purpose of listening comparisons. If amplifiers A and B both have flat frequency response, low noise floor, reasonably low distortion, high input impedance, low output impedance, and are not clipped, they will be indistinguishable in sound at matched levels no matter what’s inside them. Of course, some of the new “alphabet soup” topologies do not necessarily satisfy those conditions. "

I'd like to propose a modification to this statement:

As for amplifiers, not all amplifiers sound alike, but all amplifiers that are engineered to meet certain conditions, are correctly designed from input to output, and are manufactured without defects certainly do.​

Alluded to in earlier posts on this thread... Erroneous design implementation—perhaps including changes that were made after the initial design was released and tested—might introduce degraded audio. Further, defect errors in components or manufacturing on a particular device could effect the sound. And even subtle software bugs in drivers, embedded controllers, firmware, etc. could come into play in ways that are hard to diagnose as an end-user.

In such cases, that means someone with "good ears" will hear a difference ... and they won't be wrong. The challenge in these cases is that they are typically rare (vs. the normative experience of everyone else), which will lead to someone who has a defective device being told it is "just their ears" based on everyone else's experience with well-designed, non-defective amps / DACs / etc.