Buckeye Purifi Eigentakt 1ET9040BA monoblock power amplifier Stereophile Measurements

[Buckeye Amps]

You are not encouraging me to buy Buckeye.

You already ruled Buckeye out a long time ago so no worries here.

 

[David_M]

For any engineer the answer is clear: I look at the actual waveform and find the point where the waveform starts to clip, starting to crop off the tops of the sine (or show any other drastic deformation like slew-limiting, or protection kicking in even for short bursts). I read the voltage from the oscilloscope and calculate the power. And state that with no more than 2 significant digits.

Because that is what we want to know, the hard-clipping level as that's where things really fall apart in practical application. Distortion just below this point is irrelevant, especially if it is intentional distortion like from a tube amp or a soft-clipper.

In those typical THD+N vs Power plots, I'd use the point where the distortion starts to explode, for your example that would be 0.40kW@8R, 0.80kW@4R and 1.5kW@2R or whatever we could read from the plot if it had proper subdivisions.

Again, you realize this is very subjective from one engineer to another. My eyes might be sharper or duller than yours, so we end up with different power ratings of the same amp. Again, let the machines do the work at the set THDN level and all is good.

 

[KSTR]

Can I post a few scope plots and you tell me the distortion levels? That would be a fun game

I don't want to know the distortion levels, I want to know when hard-clipping or other final barriers on perfomance start.

 

[Jimbob54]

No, you just don't appear to understand the point that Amir has made multiple times.

Yes, why not? We dont test speakers with full power sine waves front 20Hz to 20kHz.

Amir has already engaged with the poster . Let's not rehash please .

And a polite note to all. This isn't another thread to debate regulations endlessly again .

 

[David_M]

Thats typically a very large distortion level when it becomes obvious on a scope.

Again, very subjective as I stated earlier. What you see as the start of clipping with your sharp eyes, I may see different with my duller ones. Power measurements 'by scope" is not a good or practical idea, let alone repeatable amongst several reviewers.

 

[Jimbob54]

Yes. Do you want to play the guess the distortion game?

You said that twice now . Let's not go there .

 

[tmtomh]

The necessary imperfections are to be left on electro-acoustic transducers (speakers). The electrical chain is to be as perfect as possible. The attempts to soften the requirements on amplifiers here are based on emotions.

Dude, you are one of the top two most emotional posters on this topic.

 

[rdenney]

As I’ve mentioned multiple times, there’s no requirement for the manufacturer to redesign anything -it’s simply a rating.
I believe this argument may be a red herring.

I think the analogy works well in the argument that an amplifier doesn’t need to deliver full-rated power at high frequencies since there’s typically no significant content in that range, and speakers may not handle it well.

Both arguments suggest that if we justify the performance of one piece of equipment based on the content it typically handles, we should consider applying the same reasoning consistently across other types of equipment.

It’s not simply “a rating”! How naïve. It’s the ONE primary descriptor of an amplifier’s fitness for purpose. So, an amp that makes music loud consistently with a 300W amp now gets rated at 50W just because it can’t sustain that for five minutes at 20KHz. In no way can you argue that doing so levels the playing field or clarifies the market, and you know it.

Rick “tired of people thinking of users last by pretending to put them first” Denney

 

[tmtomh]

Its not as easy as you make it to be ...

Look at the 9040 power curve below ... where is the knee at 8 ohms (thick black line)? There's a large flat plateau between 40W and 200W. What power level are you going to pick then? This amp is super clean, into 8ohms, up to ~ 390W with under -120dB THD+N.

I ask the same questions for the 4 ohms (thick red line). Flat plateaus with under -120dB THD+N up to 700W... will you pick the 400W rating at -125dB THD+N as your knee point?

View attachment 420057

Spec'ing amplifier power using the 'knee' method is fraud with problems and very subjective inaccuracies. Those amps with sharp knees will still be able to distort to 0.1% at the least. If the resolution is low and can't visually point to the 0.1% or 1%, the AP system can (or should) easily interpolate for you to get the desired power level for the distortion you are seeking for.

I'd put the 8 ohm knee at around 330 watts:

Just because the decision is not entirely cut-and-dried - you could put it at 200 where the THD starts to noticeably increase again, or as you say you could put it at 400 where the curve becomes basically veritcal - does not mean the decision is arbitrary. It's very clear where the THD suddenly and rapidly increases.

 

[pollock0424]

You are not encouraging me to buy Buckeye.

It is a free market and I strive for transparency. Dylan will definitely get my consideration..if I'm in the market to buy something that he has to offer.

PS: I tend to be an unlucky person (2 hit and runs and 3 rear-ends in past 5 years). I'm an exception and not a rule.

 

[Multicore]

Spec'ing amplifier power using the 'knee' method is fraud

Call the cops!

 

[tmtomh]

Spec'ing amplifier power using the 'knee' method is fraud

Just noticed this bit - this is total nonsense and a great example of how nuts this thread has become.

 

[Old_School_Brad]

It’s not simply “a rating”! How naïve. It’s the ONE primary descriptor of an amplifier’s fitness for purpose. So, an amp that makes music loud consistently with a 300W amp now gets rated at 50W just because it can’t sustain that for five minutes at 20KHz. In no way can you argue that doing so levels the playing field of clarifies the market, and you know it.

Rick “tired of people thinking of users last by pretending to put them first” Denney

Power rating standards promote transparency by curbing exaggerated claims, such as emphasizing high outputs during short 20 ms bursts or any other metric used to suggest "making the music louder." -Does it actually make my music louder?

It is really just a rating.
Companies can publish any ratings they like alongside the FTC rating, including their preferred "music power" ratings if they choose. Remember PMPO?
The key point here is that if all manufacturers use this one measurement (the FTC rating), it allows for straightforward comparisons among them, similar to how SINAD works. Does it give you all the information you need for your specific use case? Not necessarily, but it does serve as a performance indicator, much like the SINAD value.

If you need or want to, you can always dive into the spec sheet for more details, which may reveal metrics that are better suited for your specific needs.

IMO.

 

[pma]

The "knee method" exactly defines the point above which the output sine voltage peak amplitude, Vp, does not rise anymore. It is the clipping limit. The further increase of input voltage only leads to output signal shape broadening, thus increasing Vrms and measured power, but not increasing output amplitude. It is a good practice to measure spectrum and time plot simultaneously. Please also note that power is a derived, calculated physics value, calculated from rms voltage and load impedance. It thus makes sense to observe voltage on the X-axis, though it is not so usual.

 

[Oniiz86]

Buckeye has been a great seller/manufacturer. They took care of my SMPS issue during the late December. They wanted to work on it ASAP (on the 23rd) but I figured it is not a good idea for them to work during the holidays. I'm excited to receive my Purifi 1ET7040SA mono block back.

Also, we all have some clarification to do w.r.t rating amplifiers (especially class D). This forum is so dead set on SINAD, multi tone, and various other numbers very much past the human hearing limitations...I think that the same rule should apply to all amplifiers (and all classes). If a class D can't drive 1000watts/8ohms@15khz then it must be displayed in the specifications. You can always write a footnote about..how 1000watts/8ohms at 15khz is not really needed. I think that the same footnote should apply to the SINAD numbers that we chase here. I'm expecting full transparency from the industry and reviewers. Let the buyer make the decision. Also, note that some SMPS in class D will have Bus Pumping issues too. A well built class AB will have none of these issues except that it will weigh 50 kilos and cost $10k. One can buy a vintage amp and refurbish it, I tend to refurbish Yamaha M80s and they don't sweat it when driving my Thiel CS3.6s. I went with class D even when I knew that the power limitations/pumping could happen because...I know that these are extremes (btw, with my speakers my Buckeye Amps had bus pumping and Dylan sent me extra filtercaps and it fixed that issue).

@pollock0424 I'm assuming you purchased Buckeye's 1ET7040SA Monoblock amp with Micro Audio's SMPS1K-PFCR2 power supply, I believe that was the only option during the closeout sale, I thought it wouldn't have suffered from bus pumping without the extra capacitors pcb fitted?

 

[Buckeye Amps]

@pollock0424 I'm assuming you purchased Buckeye's 1ET7040SA Monoblock amp with Micro Audio's SMPS1K-PFCR2 power supply, I believe that was the only option during the closeout sale, I thought it wouldn't have suffered from bus pumping without the extra capacitors pcb fitted?

The extra capacitor board is included to prevent bus pumping using that specific SMPS model when playing back content under around 50Hz.

 

[pollock0424]

@pollock0424 I'm assuming you purchased Buckeye's 1ET7040SA Monoblock amp with Micro Audio's SMPS1K-PFCR2 power supply, I believe that was the only option during the closeout sale, I thought it wouldn't have suffered from bus pumping without the extra capacitors pcb fitted?

I purchased it a bit over a year ago. Back then we didn't know that this SMPS could have pumping issues. I purchased mine at full price.

 

[Oniiz86]

The extra capacitor board is included to prevent bus pumping using that specific SMPS model when playing back content under around 50Hz.

@Buckeye Amps Sorry I forgot about that, I recall now it was included, does the 1ET9040BA with Micro Audio's SMPS1K-SN power supply require the extra capacitor board to prevent bus pumping or is that not required because of the 1ET9040BA's BTL design?

 

[Buckeye Amps]

@Buckeye Amps Sorry I forgot about that, I recall now it was included, does the 1ET9040BA with Micro Audio's SMPS1K-SN power supply require the extra capacitor board to prevent bus pumping or is that not required because of the 1ET9040BA's BTL design?

Not required due to the design of the SMPS1k-SN.

 

[David_M]

Bus pumping is an issue of amplifier design, with single ended designs suffering from it and not diff ended designs by the Purifi modules. There should be no voltage sent back to the PSU on diff designs.