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Buckeye Purifi Eigentakt 1ET9040BA monoblock power amplifier Stereophile Measurements

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When is it necessary to use these amps over the 6525?

I have B&W CM10S2s with 90db sensitivity and 3.1ohm minimum impedance (6 nominal). Would I notice any difference?
 
When is it necessary to use these amps over the 6525?

I have B&W CM10S2s with 90db sensitivity and 3.1ohm minimum impedance (6 nominal). Would I notice any difference?
No. Unless you are trying to fill a cathedral, or blow out your ear drums :)
 
Not to get off topic, but having owned the Trinnov, Storm Audio, HTP-1, and Anthem AVM 70 and 90, I would highly suggest the AVM 90 and call it a day.

That's what I did (went from HTP-1 to Trinnov to Storm Audio to Anthem)
I'm really curious as to why you settled on an Anthem pre-pro. I used to own a D2v and loved it. Sold it unfortunately to help pay rent. I've always read Trinnov reviews and they said, to a point, that its RC was the best ever. So, are you saying the AVM90 Genesis (?) RC system was better than Trinnov's in your setup? I would like to get the Anthem one day when I'm more financially liquid.
 
I'm really curious as to why you settled on an Anthem pre-pro. I used to own a D2v and loved it. Sold it unfortunately to help pay rent. I've always read Trinnov reviews and they said, to a point, that its RC was the best ever. So, are you saying the AVM90 Genesis (?) RC system was better than Trinnov's in your setup? I would like to get the Anthem one day when I'm more financially liquid.
Not saying it is better, but it works (for my room) just as well. And is a lot more user friendly over Trinnov.
 
clipping and class

There is no fundamental difference between class AB and D wrt to clipping. the clipping recovery is mainly determined by the feedback loop: The feedback wants to compensate for the lacking signal amplitude during clip which gives the ‘overhang’ and possible ringing when going out of clipping. The challenge is to tell the feedback loop to ignore the past and start from a fresh when going out of clipping.

and here class AB tend to have simple 1st order loops with high unity gain frequency where as class D needs lower unity gain frequency due to the sampling nature induced by the switching frequency. This means that class D needs a higher order feedback loop to achieve enough loop gain in the audio band. A high order loop is of course more challenging to design, stabilise and control wrt to clipping recovery. The methodology and modelling tools needs has been developed since the end of the previous century with substantial contributions from my own work (eg the discrete time modelling framework) and later Bruno’s brilliant work on extending the model to self oscillating loops and any duty cycle (my model was restricted to the idle condition only). This allows optimisation of loops with staggering loop gain that are stable to nearly 100% modulation index and recovers out of clipping.

Another complication of class D over AB is that the pulses need a minimum duration. this means we cannot continuously vary the duty cycle all the way to 100%. we can only have the minimum pulse or skip it. Adding to this we have that all self oscillating loops tend to lower the switching frequency as we get to full modulation. All of this is handled by our modelling framework and optimised in Matlab even before soldering.

Note that use of higher order loops can be applied to class AB and it is a lot easier task since it can be modelled in the continuos time domain. Performance of such amp can be insane and best the best class D. The only reason this is not seen widely is that class AB designers are typically not familiar with high order control theory. Bruno and I come from a past in Sigma-Delta modulated ADC and DACs where the high order loops is a necessity.

The only but huge advantage of class D is it’s high power efficiency and compactness. Everything else is a disadvantage including the difficulty of designing it.

Rise of the noise floor during clip:
1% THD at clip means we have an error at -40dB. I don’t think that the noise normally at -130dB rising a bit and mainly above 20kHz is of any concern.
Great explanation Lars ... now, is it possible to lower the amplifier gain as one approaches clipping to prevent it from happening in the first place? Or simply lower the gain at the clipping point. One may call this a form of soft clipping?
 
I'd just like to tip my hat to ASR member and Stereophile reviewer @Kal Rubinson for his honestly and integrity in writing this review.
It can't be easy to say such positive things about this Buckeye (and his Benchmark) in a review community clan that mostly insists that you have
to spend $20,000+ to get SOTA solid state sound.
Cheers Kal.
 
you have
to spend $20,000+ to get SOTA solid state sound

... and then we have to hear that the hobby is dying. I'm not saying is the only factor, but if you read the press, the only way to have the best results is with a huge investment.

In 21th century that's not truth.
 
... and then we have to hear that the hobby is dying. I'm not saying is the only factor, but if you read the press, the only way to have the best results is with a huge investment.

In 21th century that's not truth.
Really it never has been.
 
I'd just like to tip my hat to ASR member and Stereophile reviewer @Kal Rubinson for his honestly and integrity in writing this review.
It can't be easy to say such positive things about this Buckeye (and his Benchmark) in a review community clan that mostly insists that you have
to spend $20,000+ to get SOTA solid state sound.
Cheers Kal.
Yeah, it's maybe even crazier at Computer Audiophile, or whatever it's called now. Found that place helpful when I first dipped my toe into using a Mac mini as a server to feed a Wadia CD player with a USB/SPDIF converter. Then entered the world of memory players and up conversion using HQPlayer...they were cutting edge in that regard.

But now, that forum seems to focus on stuff like multi box dCS $200K Dacs and $32K+ servers...lost of circuits in very fancy carved aluminum case work. Closest I've come to listening to that kind of gear was at an audio show that happened to take place a mile from my home. MSB room with maybe $150k of stacked DAC and amps and some well-regarded speakers...did sound very musical, authentic reproduction of voices and instruments, as good as I have ever heard. Not a controlled test...would a Okto 8 Dec driving a a Purifi amp into the same speakers, same room have sounded as good...will never know. But guessing it might come pretty close for $145K less.
 
would and Okto 8 Dec driving a a Purifi amp into the same speakers sounded as good
In the same room - and with the same DSP (if applied). Yes.

It's speakers and rooms all the way down.
 
Yeah, it's maybe even crazier at Computer Audiophile, or whatever it's called now. Found that place helpful when I first dipped my toe into using a Mac mini as a server to feed a Wadia CD player with a USB/SPDIF converter. Then entered the world of memory players and up conversion using HQPlayer...they were cutting edge in that regard.
Yes it is a shame the direction Chris took CA / AS.
A bunch of us here used to be very active members till we were told our science had no place in his subjective cable, widget, and other snake-oil threads.
Now he has a million dollar high end rig. :facepalm:
Bye Chris
 
CA re-direction may have something to do with the "audio as jewelry" corporate sponsors?

Not sure I have see a measurement or a tech stat in a recent CA review. Plenty of focus on more boxes/converters/heavy casework/custom shipping cases..."assaults on the state of the art" or perhaps assaults on the wallets of folks who believe they "deserve the best".

Once asked if CA could do a review of a Topping DAC versus a dSC or a Purifi versus a Constellation $30K stereo amp with a well-respected reviewer min same system/room...crickets.
 
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Yes it is a shame the direction Chris took CA / AS.
A bunch of us here used to be very active members till we were told our science had no place in his subjective cable, widget, and other snake-oil threads.
Now he has a million dollar high end rig. :facepalm:
Bye Chris
I was very proud to be booted off CA after I called out some of the woo and false claims. :)
 
Yes it is a shame the direction Chris took CA / AS.
A bunch of us here used to be very active members till we were told our science had no place in his subjective cable, widget, and other snake-oil threads.
Now he has a million dollar high end rig. :facepalm:
Bye Chris
Yep. That process seemed very clearly to be about clearing away factual, science-based discussion to make way for upmarket growth of the site and its advertising revenue. It happened more out in the open than it ever would at a more conventional magazine-style publication - which made it kind of fascinating to watch.

I actually am mostly live-and-let live about it - it’s Chris’s site and he can do as he wishes. The one aspect that really did bother me, though - and the reason I won’t participate there anymore - is that the “Objective-Fi” subforum ghetto he created to restrict science-based discussion quickly became something much worse than that. It became filled with topics and comments by anti-science members who used indiscriminate, unscientific questions and bad-faith arguments to make a mockery of the entire enterprise of science-based discussion and understanding of audio. And I view that as an actively and gratuitously negative phenomenon. Basically Chris herded the objectivists into a virtual pen, told them it was necessary for the good of the community, and then let all the most rabidly anti-science members of the site flood into that pen to throw things at them. It’s just an online hobby discussion forum, but the pattern of Chris’s behavior and how he justified it has pretty strong parallels to various historical actions and rhetoric in real-workd situations where the consequences were very real.
 
Yep. That process seemed very clearly to be about clearing away factual, science-based discussion to make way for upmarket growth of the site and its advertising revenue. It happened more out in the open than it ever would at a more conventional magazine-style publication - which made it kind of fascinating to watch.

I actually am mostly live-and-let live about it - it’s Chris’s site and he can do as he wishes. The one aspect that really did bother me, though - and the reason I won’t participate there anymore - is that the “Objective-Fi” subforum ghetto he created to restrict science-based discussion quickly became something much worse than that. It became filled with topics and comments by anti-science members who used indiscriminate, unscientific questions and bad-faith arguments to make a mockery of the entire enterprise of science-based discussion and understanding of audio. And I view that as an actively and gratuitously negative phenomenon. Basically Chris herded the objectivists into a virtual pen, told them it was necessary for the good of the community, and then let all the most rabidly anti-science members of the site flood into that pen to throw things at them. It’s just an online hobby discussion forum, but the pattern of Chris’s behavior and how he justified it has pretty strong parallels to various historical actions and rhetoric in real-workd situations where the consequences were very real.
I wasn’t familiar with that place. I spent 10 minutes reading, and I won’t spend another one.
This particular thread is a tough read:
 
I wasn’t familiar with that place. I spent 10 minutes reading, and I won’t spend another one.
This particular thread is a tough read:
…. With well known participants like F. Some time ago I have decided not to try to debate on similar basis with golden ear owners. It goes to nowhere and the only effect is lost time. As getting old, I realize I do not have time enough to spend it in pointless debates and quarrels. Best ignored.
 
Basically Chris herded the objectivists into a virtual pen, told them it was necessary for the good of the community, and then let all the most rabidly anti-science members of the site flood into that pen to throw things at them. It’s just an online hobby discussion forum, but the pattern of Chris’s behavior and how he justified it has pretty strong parallels to various historical actions and rhetoric in real-workd situations where the consequences were very real.
Very clearly observed and well said.
What's funny is how obvious he makes it all look.
I remember his thread some years back asking for recommendations for his new speaker system.
All of a sudden he chose Wilson, and forever since there's been HUGE full width Wilson ad at the top of his pages.
It's all about the money over there. :facepalm:
Moving on ---------------------------
 
I believe the following observations may be useful to some people who are wondering why anyone's Purifi amps do not match Purifi's datasheets, at least for the 1ET9040BA module.

1. Nowhere in the 1ET9040BA datasheet is the power supply module used for the datasheet specs listed.. For all we know, they could have used an industrial beefed up lab bench power supply for their tests! But no Hypex PS listed anywhere in the datasheet. This is a serious and glaring oversight imho. It could explain why no vendor is able to get the datasheet spec'd 1% THD 1400W of power in 2 ohms using the recommended Hypex PS.

March Audio says the Hypex PS are able to produce ~1100W in 2 ohms, hence they use a different non-Hypex power supply in the mono amps. Not sure if its from MicroAudio or other PS vendor.

2. The 1ET9040BA specs are only achievable in mono configuration, i.e. one power supply per module. If you a Hypex (or even MicroAudio) PS is shared among two 9040BA modules, a stereo configuration, you will never see the rated datasheet power specs. Simple math guarantees that will never be the case.

3. I see VTV Amplifiers rates one of their 9040BA monoblocs @928W continuous into 2 ohms per their AP measurements. But not sure why they managed to measure their dual mono amps with 2 power Hypex supplies at 1.35kW rms into 2 ohms @1% THD. The math is not mathing right, imho.

@Buckeye Amps , can you please help put this conflict to rest? How much power is available from the 1ET9040BA using the recommended Hypex A180 power supply at 2 ohms with 1% THD. Thanks!

EDIT .. the datasheet says the 9040BA achieves 1400W into 2 ohms at 0.1% distortion. This doesn't sound right and maybe its a typo. They rate all their other old and new generation amps at 1% THD for 8, 4 and 2 ohms, when applicable. The 0.1% implies its capable of even higher than 1400W of power at 1% THD.
 
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@Buckeye Amps , can you please help put this conflict to rest? How much power is available from the 1ET9040BA using the recommended Hypex A180 power supply at 2 ohms with 1% THD. Thanks!
Can't you just read that off their website?

 
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