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Buckeye Purifi Eigentakt 1ET9040BA monoblock power amplifier Stereophile Measurements

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@Buckeye Amps : I do not want to give you advices, but if I was to make a decision on outgoing Q&C control on every piece, I would definitely test for:

1) frequency response at mid power level,
2) THD, THD+N at 1kHz at -1dB below rated power,
3) CCIF 19+20kHz IMD at -1dB level below rated peak output voltage amplitude.
This is no cherry picking, but it would prevent you from sending the unit that has an evident issue. Of course stepped sine tests would be good to make as well.

You advertise this:

  • 1200 watts @ 2 ohm
  • 750 watts @ 4 ohm
  • 375 watts @ 8 ohm
  • (per channel, 1kHz, 0.1% THD, Hypex SMPS)
  • S/N: 140dB
  • FR: 0 - 80KHz
  • THD: 0.0001% (400W, 4Ω, 20Hz-20kHz)


Is that all correct?
 
Discussed this with Kal and Jim Austin this morning, Dylan. We are in agreement that you should ship a pair of amplifiers to me for measurement. If both are behaving correctly, Kal will then audition them and Stereophile will publish a followup.

I'll email you with my shipping address.

John Atkinson
Technical Editor, Stereophile
Thank you John. While doing this it would be great to hear what you, Jim, or Kal think about the following:

First, there’s a long discussion thread here regarding the efficacy of the new FTC requirements for reporting amplifier power specifications. There is a contingent here that believes the requirement is poorly thought out and disadvantages class D amps specifically. Another group feels the requirement is reasonable and will help differentiate amplifiers for consumers. This seems like an issue that Stereophile’s writers would have opinions on - it would be interesting to hear from you and your colleagues.

Second, another related thread here involves reported class D power specifications. If I understand the discussion correctly, many class D amplifiers can produce large amounts of power on demand but are only able to deliver a fraction of that power on a continuous basis. The bone of contention seems to revolve around the relevancy of this in real world listening environments. Again, hearing what you think in the pages of Stereophile would be welcome.

And Merry Christmas!
 
Thank you John. While doing this it would be great to hear what you, Jim, or Kal think about the following:

First, there’s a long discussion thread here regarding the efficacy of the new FTC requirements for reporting amplifier power specifications. There is a contingent here that believes the requirement is poorly thought out and disadvantages class D amps specifically. Another group feels the requirement is reasonable and will help differentiate amplifiers for consumers. This seems like an issue that Stereophile’s writers would have opinions on - it would be interesting to hear from you and your colleagues.

Second, another related thread here involves reported class D power specifications. If I understand the discussion correctly, many class D amplifiers can produce large amounts of power on demand but are only able to deliver a fraction of that power on a continuous basis. The bone of contention seems to revolve around the relevancy of this in real world listening environments. Again, hearing what you think in the pages of Stereophile would be welcome.

And Merry Christmas!

Personally, I don't care about FTC requirements. But if a company posts a specification, it should be valid and be able to be verified throughout random monthly production measurement checks. If that's not the case, and several reviews show inadequate quality control it impacts my desire to recommend or purchase from the organization.

Every company makes an occasional mistake or has an unforeseen manufacturing issue. It's how they handle it and work through it to avoid the same issue repeating over multiple products that impacts my shopping decision.
 
Is mandatory for Purifi to publish the bad batch S/N.
Failing to do that will only put more gas at the speculating fire and the jokes around audio forums.

In fact it's not me who should insist on this,but their direct clients like Buckeye who trust them that their products is sound so they don't have to rigorously test every single one of them but only the usual safety and sanity tests.
Of course the exact same products are sold for DIY and knowing that a bad batch is out there is not exactly reassuring if one plans a nice built.

The direct victim I see here is only the reviewer who gave a good review (proving from my point of view that the craziness about this specs down the void of inaudibility is at least exaggerated) but will not get away from the bitterness of the bad willing known suspects around the audio community about its reviewing skills any way.
 
If I understand the discussion correctly, many class D amplifiers can produce large amounts of power on demand but are only able to deliver a fraction of that power on a continuous basis.
I don't think that is in any way related to amplifier operating class. Most amplifiers are limited in terms of continuous power by their power supplies.
 
The direct victim I see here is only the reviewer who gave a good review
He gave a good review and should not be blamed for anything. He tested what he received and he is not obliged to study datasheets and speculate what's and why's. In fact the wide set of measurements in Stereophile, like that 50W/8ohm CCIF IMD, has discovered something that would probably remained hidden with a "soft" 5W CCIF test as performed occasionally at ASR. The module issue should had been found by both the manufacturer and the assembler. Then, they would prevent that "publicity".
 
The direct victim I see here is only the reviewer who gave a good review (proving from my point of view that the craziness about this specs down the void of inaudibility is at least exaggerated) but will not get away from the bitterness of the bad willing known suspects around the audio community about its reviewing skills any way.
Not sure what the bitterness would be. It again proves that subjective, sighted reviews are of rather limited value compared to proper measurements.
 
He tested what he received and he is not obliged to study datasheets and speculate what's and why's.
From what I remember in SP audio review and measurements are done in parallel and don’t speak together until both are finished.
 
I don't think that is in any way related to amplifier operating class. Most amplifiers are limited in terms of continuous power by their power supplies.
Yes but those small cheap class D boxes are limited by poor thermal design.
However, this is off-topic in this thread.
 
8 ohms - "amplifier went into protection at 290W" - (77% of Buckeye power claim of 375W)
4 ohms (fig.5), it did so at 450W - (60% of Buckeye power claim of 750W)
2 ohms (fig.6), it turned off at 660W - (55% of Buckeye power claim of 1200W)

This doesn't seem like a small miss to me. If these results were achieved in an ASR review wouldn't it likely be considered a major failure with a panther head rolling on the floor?
It now seems pretty clear that the Purifi module in the amplifier that Stereophile tested was defective. So... really nothing to talk about for this particular amp/test until that's straightened out, is there?
 
From what I remember in SP audio review and measurements are done in parallel and don’t speak together until both are finished.
That is fine. No arguing on this.
 
It now seems pretty clear that the Purifi module in the amplifier that Stereophile tested was defective. So... really nothing to talk about for this particular amp/test until that's straightened out, is there?
But probably not the single one particular module. As per their facebook statement:

PURIFI Audio

Saturday, December 21, 2024 at 11:09 AM

Statement related to 9040 modules
In June 2024, we delivered a small number of pilot production units that had passed outgoing screening but were later found to contain an issue affecting high-frequency performance. We have since corrected and expanded our QC procedure to ensure such issues do not occur in all successive batches.
All production units now meet specifications. However, it appears that a faulty unit was not recalled in time and was apparently used in a product sent for review. We are very sorry for the mistake and are working closely with our OEM partners to ensure a replacement is provided as quickly as possible.

PURIFI Audio
 
The direct victim I see here is only the reviewer who gave a good review (proving from my point of view that the craziness about this specs down the void of inaudibility is at least exaggerated) but will not get away from the bitterness of the bad willing known suspects around the audio community about its reviewing skills any way.
This assumes that the fault is audible. There's so much discussion recently on audibility of performance metrics. There are some things which should be SOTA, but which when flawed, we humans simply can't hear the flaw with music.
 
FWIW: we have our own data from months ago showing no issue with the amp going into protection during power sweeps and also meeting the power spec goals.

As I have said in our official thread, we will be doing more testing in the new year to further back up what we have already observed on our end.

I am in no way saying JA did anything wrong, is faulty, etc. It is something that at this moment can't be explained and is at odds with previous data. So being the trained scientist I am, will not begin to speculate or draw conclusions until more data is collected and added to the mix.
Well said
 
A correct assumption as it turned out.
Sorry. Not. The issue had nothing to do with the case material. As I understand the explanation it was a result of a component manufacturing fault.

The best you might get in respect of the output inductor being wrong is that it was manufactured with the wrong material, gap or number of turns. That sort of mistake happens because production of such low volume items has humans in the loop. If it was the inductor then they probably build them and then test them at zero bias at a fixed frequency on a Simpson VOM. If so I guess that pre-production testing will have been tightened.

A self oscillating amplifier relies on operating on the point of instability. Part of that in terms of operating bandwidth will be the value of the output inductor.

Eigentakt drives that to it limits by including additional gain stages within the loop with those stages being dropped in and out according to operating conditions including output level. Even if you don't get it exactly right it can still be very forgiving to the extent that, in an early stage release, your product will 'look good' rather than immediately going futz before it gets out of the door.

Again rather than babbling about the case material being the issue you would be better to guess, and likely still be wrong, that level may have been the indicator given that the amplifier adjusts its loop gain to maintain oscillation at a particular, working/workable frequency without totally losing the plot.

Loss of loop gain, something got switched out prematurely, might go some way to explaining the higher distortion for the test that was being done. Cause and effect.... The amplifier exceeded its claimed distortion figures before it hit its claimed output power. Presumably if that was ignored and it was just driven harder then. assuming it did not hit thermal limiting, it would have met the power spec.

OK. An example of an early stage product as released for review did not hit the spec but they have been called for it, identified the issue and taken action to catch future mistakes before they get out of the door. Well done everyone. Thanks for the input. Good Catch. No we will not be using a different shade of blue on the cases unless you require that specific option.

In respect FTC requirements, which appears to be an aside to this discussion, assuming a manufacturer states the conditions under which they will claim specific performance for their product then they should be measured against such claims, as as happened here, rather than any poorly considered constraints placed upon them by a regulator trying to level the playing field. To me that just introduces a different opportunity for snake oil to the equation when it would be better to, rationally, challenge the snake oil that is already being used.
 
They are done in series with the audition before any measurements.
Thanks for clarifying. Results at about the same and doing this separately makes a lot of sense.
 
@Buckeye Amps : I do not want to give you advices, but if I was to make a decision on outgoing Q&C control on every piece, I would definitely test for:

1) frequency response at mid power level,
2) THD, THD+N at 1kHz at -1dB below rated power,
3) CCIF 19+20kHz IMD at -1dB level below rated peak output voltage amplitude.
This is no cherry picking, but it would prevent you from sending the unit that has an evident issue. Of course stepped sine tests would be good to make as well.

You advertise this:




Is that all correct?
Every piece? So if I am following most of these threads correctly, we audiophiles: don't want it made in China, want SOTA performance, zero defects, now AP tests of every unit AND keep it under $1,200?? On another thread, a member actually stated that speakers should have distortion tests at 105-115db. Ridiculous.
 
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