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Buckeye Purifi Eigentakt 1ET9040BA monoblock power amplifier Stereophile Measurements

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I want to take this opportunity to make it publicly known (if there was any doubt) that I am in no way going to let Purifi take the blame/criticism all alone that some might throw at them.

Ultimately they made the modules and released them to the market. Only they know the full number of modules released and the serial numbers and thus the simplest, easiest way to make this right is for them to be forthcoming. I can see no legitimate reason to not release the serial numbers so that end users can find peace of mind. It would be nice to believe that only one module escaped their recall but it would be better for everyone if they simply disclosed the serial numbers. I see no reason for the hesitancy. While nice to know that Purifi contacted their customers about the recall, the fact that one module escaped means that others could have as well.

Offering to verify numbers privately is of help but I have never seen a recall where the numbers aren't made available for the buying public. Again, trust but verify.

Buckeye is not to blame for the issue itself though if they were told which modules were defective and used one by mistake certainly that is their fault but an honest mistake.
 
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Ultimately they made the modules and released them to the market. Only they know the full number of modules released and the serial numbers and thus the simplest, easiest way to make this right is for them to be forthcoming. I can see no legitimate reason to not release the serial numbers so that end users can find peace of mind. It would be nice to believe that only one module escaped their recall but it would be better for everyone if they simply disclosed the serial numbers. I see no reason for the hesitancy. While nice to know that Purifi contacted their customers about the recall, the fact that one module escaped means that others could have as well.

Offering to verify numbers privately is of help but I have never seen a recall where the numbers aren't made available for the buying public. Again, trust but verify.

Buckeye is not to blame for the issue itself though if they were told which modules were defective and used one by mistake certainly that is their fault but an honest mistake.
My guess, based on knowing the likely amount of modules involved (from extrapolating how many I was allocated in the initial batch), is the production run affected was very small. If (hypothetical) 50 were affected and they had 49 returned in hand back in the Fall and now know where the 50th module ended up, what is the point?

As to how mine slipped through: nothing nefarious on my part. Either I did not get the email (spam filter, failed to send) or it could have been as "simple" as one serial number was improperly transposed when Purifi checked their logs, who knows. Either way, I am not going to delve into any type of speculative or conspiracy ruminations.

Regarding the direct sale of modules: the production run of those affected were not sold directly to customers at that time so that is also a non-factor in this. Only OEM's were affected, so it makes sense to have them handle the issue (which, again, was months ago).

Also, if I was Purifi, another reason I wouldn't just blast the numbers into the public but instead work with their OEM's is safety. What if someone decided to open up their amp without first contacting the OEM/company and something happened? A person might argue (in court) that by releasing the serial numbers, Purifi was suggesting for customers to open their amps to check their module(s) without any guidance or consultation from the OEM. This could make Purifi responsible if something happens (electrocution, damage, etc).
 
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Offering to verify numbers privately is of help but I have never seen a recall where the numbers aren't made available for the buying public
Warning another car analogy.

The way some recalls are done on vehicles in the US they will state certain vehicle models are under a recall and you have to put the VIN number in to see if you're affected.
It calls for positive action from the owner. The public knows i.e. a Subaru Outback is under recall for x issue but the only way to know if your Outback is under recall is to input your VIN number.

Sort of like looking at your amplifier and giving the serial number to Purifi or the manufacturer you purchased from to see if your module is affected.

There's also silent recalls which I had on a 2009 Honda Accord. Wasn't even aware there was one until they replaced my brakes for free when I took it in for an oil change.
 
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Sorry, just saw this as was down with the flu...

Correct, your statement about previous root cause testing is accurate. Was working with Buckeye at the time and we comprehensively tested other potential solutions (tightening, soldering, etc.) before the designer found the ferrous content of the binding post tab. A summary of that investigation was posted here. The "faulty" tab is part of the binding post and was determined to have ferrous content. So fortunately, ended up a simple fix.

Newer Buckeye amplifiers (like the Stereophile test unit) use an improved binding post and it has fewer parts. None of the new binding post parts have ferrous content.

With binding posts, another improvement is to have a slit connecting the two holes where the binding posts go. So, not two Os but a kind of “lifting weight” figure. So the two opposite signals cancel and there is no eddy current around the conductors that could cause some distortion, and reduces the advantage of Speakon connectors to the robustness of their locking. This was told me by Kim Nordtorp Madsen (IIRC).

Roberto
 
Clipping comparison (THD10%), in higher resolution, of class AB amplifier and Purifi 1ET400A, into 8ohm. One can see 20dB noise penalty of the Purifi module (SNR 38dB vs. 58dB), much higher noise floor when clipping. This is the clear evidence, hard data. Please take into account that the PSU of the Purifi module is NOT overloaded and yields quite clean output when thePurifi module is clipping. Much cleaner than the linear PSU in the class AB amplifier under clipping conditions. However, the class AB amp is cleaner with higher S/N when pushed hard to clipping. At 20Hz, the situation is similar.

1ET400A_8R_1kHz-THD10%.png


A250W_8R_1kHz-THD10%.png



and a direct comparison - BIG difference.

1ET400A-A250W_8R_1kHz-THD10%.png
 
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Offering to verify numbers privately is of help but I have never seen a recall where the numbers aren't made available for the buying public. Again, trust but verify.
All that means is you haven't had a registered product where that occurred. How would you know there haven't been dozens, hundreds, thousands, etc. of private recalls?
 
regarding serial numbers and the recall of faulty units:

As we stated earlier: it was a pilot run from June that subsequently was recalled which means we notified the recipients (OEM early adopters). One of these modules somehow managed to escape the recall and ended up being reviewed. It is very unlikely that there are any more modules escaping the recall and even less likely that they ended in the hands of end users. We are of course double checking our logs to verify and will act accordingly but it takes a bit more time due to the holidays.

If anyone owning a 9040 still wants reassurance they are very welcome to query us with their specific serial numbers and we will check after the holidays.

Again, a recall means that we contact the owners directly and this recall was some time ago. Volume production has been running since then and the end of line test tightened.

The only reason we did a public statement was due to the review of a likely faulty module which could cast doubt about the modules general performance or the end product integration. Again, a recall means that we contact our customers directly.

Happy New Year to everyone!

Thanks Lars!

Since it was a small pilot lot, gather Purifi had good tracking on who received units. Frankly, know other companies that would have only bothered to recall if the issue posed a safety or a reliability issue. This appears to be a relatively minor performance issue. Since we are just hearing of it due to the Stereophile review, gather not many of Purifi's OEMs found it either.

Happy New Year and enjoy your holiday!
 
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Clipping comparison (THD10%), in higher resolution, of class AB amplifier and Purifi 1ET400A, into 8ohm. One can see 20dB noise penalty of the Purifi module (SNR 38dB vs. 58dB), much higher noise floor when clipping. This is the clear evidence, hard data. Please take into account that the PSU of the Purifi module is NOT overloaded and yields quite clean output when thePurifi module is clipping. Much cleaner than the linear PSU in the class AB amplifier under clipping conditions. However, the class AB amp is cleaner with higher S/N when pushed hard to clipping. At 20Hz, the situation is similar.

View attachment 417006

View attachment 417007


and a direct comparison - BIG difference.

View attachment 417016
thanks for the plots. Apart from the 10% harmonics, (-20dBc), the dominant ‘noise’ components of the -38dB ‘noise’ are 100Hz ripple modualtion side bands. these are related to the power supply mains ripple and not a function of the amp. this goes also for the AB amp spectrum. These plots tell more about the power supplies than the operating class of the amps.
 
Not quite. My reading and understanding is that these wee pre production samples. Thisxhas been mentioned several times. I expect these were not intended or expected to be sold to customers. For info I asked March Audio about it. Their statement here.
If you bought an smp from a manufacturer contact them for guidance. If you bought a module direct from Purifi contact Purifi. Lars has said they are glad to help.
Not going to get involved in March's business, but will comment that our (2) Pre-Production modules were NOT used in any customer builds. I know thin_blue on those forums would love to say otherwise, but that is not the case at all. Going to nip that in the butt real quick.
 
For info I asked March Audio about it. Their statement here.
"The board wasnt optimally calibrated and a simple tweak of a pot on the board and problem was solved."

What pot did he adjust? Can't imagine he can compensate for the protection diode being misplaced with any kind of adjustment this way.
 
Coming from the position of not believing a word March Audio says about any field issues with his products, I would say nothing useful comes out of asking him about such matters unless independently verified.
 
Clipping comparison (THD10%), in higher resolution, of class AB amplifier and Purifi 1ET400A, into 8ohm. One can see 20dB noise penalty of the Purifi module (SNR 38dB vs. 58dB), much higher noise floor when clipping. This is the clear evidence, hard data. Please take into account that the PSU of the Purifi module is NOT overloaded and yields quite clean output when thePurifi module is clipping. Much cleaner than the linear PSU in the class AB amplifier under clipping conditions. However, the class AB amp is cleaner with higher S/N when pushed hard to clipping. At 20Hz, the situation is similar.

View attachment 417006

View attachment 417007


and a direct comparison - BIG difference.

View attachment 417016

So, when you drive a Class D amp and a Class AB amp to extreme distortion levels, the Class D is worse. But then, they cannot be both 10%, right?
Also, isn’t this a bit artificial?
 
Or perhaps 2 different issues?
I am going by his claim that he individually tests each amp so would have caught the real (diode) issue. Unless each amplifier comes with such tests and is certified to be that serial number, I don't accept any such claim from him as being factual.
 
A person might argue (in court) that by releasing the serial numbers, Purifi was suggesting for customers to open their amps to check their module(s) without any guidance or consultation from the OEM. This could make Purifi responsible if something happens (electrocution, damage, etc).

OEM places serial numbers of internal equipment on the outside of the box. Tracing Problem Solved?
 
"The board wasnt optimally calibrated and a simple tweak of a pot on the board and problem was solved."

What pot did he adjust? Can't imagine he can compensate for the protection diode being misplaced with any kind of adjustment this way.

OK. I'll go Chicken Little. On the assumption that "the protection diode" is intrinsic to the circuits that switch gain stages in and out in order to maintain a stable loop under all operating conditions, not a 'protection diode'. What on earth is a diode doing, along with its temperature coefficient of whatever, that requires the adjustment of a 'pot' such that that is not going to go out of spec in -100dB vs -120dB distortion terms when something warms up (under FTC rules?) I'll assume that Purifi is better than that and the pot is not there... or the diode.
 
OEM places serial numbers of internal equipment on the outside of the box. Tracing Problem Solved?
Uhm no.
Try running a company where you manufacture a product and over time you'll understand why you don't want to do this.

What manufacturers do ... they track the SN numbers for components used in manufacturing by lots.
NOTE: YMMV depending on the product and the component. So if something goes wrong... based on the SN of the reported problems... they can narrow it down and alert their customers and/or distributors. There's a bit of work behind this... and its a lot of data depending on your product. Think about it.
And data acquisition can be a royal pain in the arse and can involve supply chain issues, relying on the supplier to provide some of this data electronically.

What you suggest isn't really feasible. Just pretend you're a company and work thru the problem.

I have to give Dylan credit. He's got a thicker skin than most.
I don't know how many could have resisted the temptation to get in to a flame war defending their product.
 
I'll assume that Purifi is better than that and the pot is not there... or the diode.

Lars himself stated there was a misplaced (reversed?) diode.
Diodes are often implemented in protection/limiting roles.
There is a pot on the board. You can see it.

pot.JPG
 
Not quite. My reading and understanding is that these wee pre production samples. This has been mentioned several times. I expect these were not intended or expected to be sold to customers. For info I asked March Audio about it. Their statement here.
If you bought an smp from a manufacturer contact them for guidance. If you bought a module direct from Purifi contact Purifi. Lars has said they are glad to help. I really would not encourage people to open up their amps to find serial numbers. It could be dangerous.
It sounded from the wording on Alan’s site that they found the problem and “rectified” it.
(That seems like it sort of deserves a bonus point.)

Also:
{via MARCH AUDIO] This is a good demonstration as to why we individually test every amplifier after build. It ensures problems such as these don't get to customers. So any customer that has purchased our P801 amplifiers can rest assured that it doesn't have the Buckeye high IMD problem and works to specification.
 
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