Buckeye Amps: 2nd Generation Purifi EIGENTAKT 1ET9040BA Amplifier

[ggs]

A quick look at the OPA 1656 data sheet shows a much better than JA measured CCIF IMD at 3 VRMS out. So this idiot still wonders why the JA measurement looks the way it does. Did you measure the IMD Dylan? If so, what did you measure?

 

[Buckeye Amps]

A quick look at the OPA 1656 data sheet shows a much better than JA measured CCIF IMD at 3 VRMS out. So this idiot still wonders why the JA measurement looks the way it does. Did you measure the IMD Dylan? If so, what did you measure?

Yes but not the 19kHz + 20kHz that Stereophile measured.

 

[ggs]

Thank you for sharing that. If you ever discover why the measurements differ, please let us know.

 

[Matias]

Review now live.

Buckeye Purifi Eigentakt 1ET9040BA monoblock power amplifier

Back in 2016, I documented the rise of class-D amps using the early TriPath technology. Used in the Bel Canto eVo 200.2, TriPath cracked open the door to the High End but was never admitted due to a dim and opaque treble. The second wave was based on B&O's ICEpower technology, again via a Bel...

www.stereophile.com

 

[Fahzz]

"superb". You're gonna be busy! Good for you.

 

[yys310]

Is it broken?
What's wrong with the IMD?
Also
"The input impedance is specified as 51k ohms. However, I measured 8.4k ohms from 20Hz to 20kHz. This was not affected by the gain setting."

 

[pogo]

What's wrong with the IMD?

The test frequencies should be increased and decreased in order to narrow down the 'problem area'.
Or was this just an isolated case that slipped through the final (implementation) check?

 

[Matias]

"superb". You're gonna be busy! Good for you.

Yes, Buckeye is well known in our ASR bubble, but a positive review on Stereophile brings crazy exposure to pretty much everyone else.

 

[welwynnick]

Yes, Buckeye is well known in our ASR bubble, but a positive review on Stereophile brings crazy exposure to pretty much everyone else.

For something that I hoped would be the best amplifier ever, I didn't think it was a very positive review.

 

[Julf]

For something that I hoped would be the best amplifier ever, I didn't think it was a very positive review.

Buckeye hasn't advertised enough in stereophile?

 

[welwynnick]

Buckeye hasn't advertised enough in stereophile?

I think Kal is reasonably partial to this part of the market, and the measurements fell a long way short of what I was hoping to see. Good at 1kHz, but not elsewhere.

 

[Matias]

While measurements are below what is expected, overall it was positive so the point (huge exposure) remains.

 

[welwynnick]

While measurements are below what is expected, overall it was positive so the point (huge exposure) remains.

That's true, but a lot of Stereophile reviews are positive. They're very good (or bad, depending on your point of view) at disguising their opinions, and it's rare for them to come down firmly in favour or against a particular product. This applies to many audio reviewers of course (Amir excepted). With Stereophile you often have to dig quite deep and read between the lines to find what you want to know. They often damn with faint praise, and it takes a while to recognise it. Having read Stereophile for decades, this didn't strike me as one of those "go out and buy it now!" reviews

 

[EdW]

You probably need to have a bit of technical understanding to read the review and come away thinking WTF. People might not read or understand the measurements section where it shows massive IMD and shutting down at half power. Didn't Buckeye test it before sending to Stereophile?

There are a few slightly worrying aspects to the 9040 amps performances
1. Reports of damage (to other 9040 based designs - not Buckeye I would hasten to add) when shorted - shouldn’t happen - has the protection mechanism been set by Purifi to trip early to safeguard this?
2. In the case of this Buckeye amp we would have expected this amp to deliver nominal performance into 8 and 4 ohms but be restricted by the rather limited output of the Hypex SMPS when delivering into 2 Ohms. The alternate power supply option available soon should fix this.
3. IMD not aligning with data sheet - long way out
4. Rise in distortion at the top end of the audio band - to some extent expected with a class D design and shouldn’t matter since any distortion would most likely fall out of band. But this appears to be a little more than expected. Related to the IMD problem?

I assume both amps were tested by John Atkinson when the performance discrepancy was noted but either way this needs to be investigated to establish root cause.

 

[EdW]

That's true, but a lot of Stereophile reviews are positive. They're very good (or bad, depending on your point of view) at disguising their opinions, and it's rare for them to come down firmly in favour or against a particular product. This applies to many audio reviewers of course (Amir excepted). With Stereophile you often have to dig quite deep and read between the lines to find what you want to know. They often damn with faint praise, and it takes a while to recognise it. Having read Stereophile for decades, this didn't strike me as one of those "go out and buy it now!" reviews

But if any audio equipment passes the hyper critical ASR community scrutiny then it’s damn good!

 

[welwynnick]

Maybe Stereophile test amplifiers in a slightly different way; it doesn't just have to be about frequency, impedance and distortion.

I believe JA pre-conditions the amp to warm it up beforehand. This might result in protection intervention at a lower power level than with other testers.

The duration of the test may be different as well. A power test over a long period of time may give a lower result than a short term test.

Neither of those issues would cause me any concern, but it would be good to have an explanation. Aside from the input impedance, it's hard to believe that anything Buckeye do with the Purifi module would cause the issues arising.

 

[pma]

Maybe Stereophile test amplifiers in a slightly different way; it doesn't just have to be about frequency, impedance and distortion.

I believe JA pre-conditions the amp to warm it up beforehand. This might result in protection intervention at a lower power level than with other testers.

The duration of the test may be different as well. A power test over a long period of time may give a lower result than a short term test.

Neither of those issues would cause me any concern, but it would be good to have an explanation. Aside from the input impedance, it's hard to believe that anything Buckeye do with the Purifi module would cause the issues arising.

Stereophile measurements are correct. I described the almost certain reason here:

Buckeye Purifi Eigentakt 1ET9040BA monoblock power amplifier Stereophile Measurements

This is an interesting review - https://www.stereophile.com/content/buckeye-purifi-eigentakt-1et9040ba-monoblock-power-amplifier-measurements and we can see that the amp did not meet the datasheet specs. First, I would like to comment on CCIF IMD 19+20kHz result: @John Atkinson measured this...

www.audiosciencereview.com

 

[quattro98]

Stereophile measurements are correct. I described the almost certain reason here:

Buckeye Purifi Eigentakt 1ET9040BA monoblock power amplifier Stereophile Measurements

This is an interesting review - https://www.stereophile.com/content/buckeye-purifi-eigentakt-1et9040ba-monoblock-power-amplifier-measurements and we can see that the amp did not meet the datasheet specs. First, I would like to comment on CCIF IMD 19+20kHz result: @John Atkinson measured this...

www.audiosciencereview.com

According to the Buckeye website, the enclosure is made of aluminum. The manufacturer is reported as Protocase. Having an additional set of independent measurements would be nice to compare.

 

[Sokel]

I very much doubt it is any fundamental issues with the Purifi 9040 modules. Their data sheets have always been accurate and show none of the issues seen here. I raised concerns previously about Buckeyes input buffer from the limited data he posted. Distortion and noise.
IMD and THD are fundamentally related.

I am really,REALLY curious about what PSU Purifi uses for their tests.
Does anyone know?

 

[Buckeye Amps]

I am really,REALLY curious about what PSU Purifi uses for their tests.
Does anyone know?

Per Purifi when I inquired once, an "industrial" power supply that allows for very stringent/fixed voltage output with very little voltage drop even at max power output.