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Buckeye Purifi Eigentakt 1ET9040BA monoblock power amplifier Stereophile Measurements

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Just to be boring...

https://www.hypex.nl/products/smps-family/smps1200a100

The SMPS1200 is designed with a selectable input voltage range, allowing it to accommodate various power input specifications.

As someone else has mentioned this is likely done via a link in the input bridge to configure the unit for direct rectification or voltage doubling. The unit(s) do not include power factor correction. I may be wrong but the 110V selection, to presumably double, may give higher ripple on the primary side bulk. Of course Purifi, and other ClassD implementations have impressive PSSR.

2 x 31 (Min), 2 x 40 (Typ), 2 x 46 (Max) Vdc - [B]Proportional ta [SIC] AC Mains[/B]

Indicates that the supply is not, secondary to primary side, regulated. Ignoring how people may feel about regulated power supplies this is likely to be that the topology is an LLC convertor operated open loop because compensation of such loops is a 'dark art'. Such convertors, without feedback, are common in Pro Audio amplifiers...

https://www.ti.com/lit/an/slua582a/slua582a.pdf?ts=1736573689053

This application note describes an approach to design feedback loop compensation for an LLC resonant
half-bridge power converter. The approach described here is based on the measured Bode plots of the
modulator generated by a network analyzer. As we know, as long as the modulator Bode plots are
obtained, the frequency domain poles and zeros in the feedback loop compensation can be analytically
determined, then fine-tuned with a bench test. This measurement is necessary as part of feedback loop
design because a practical small-signal model is not available for LLC resonant converters.


Other horrorshows are also involved. In particular the design of your LLC transformer but overall it's not unsurprising that people will choose to implement an LLC convertor operated open loop just inside the inductive region [1] for supposed efficiency reasons then iterate it until it does not blow up and then not bother trying to regulate things especially when TI appear to achieve a whole 10KHz bandwidth.

The whole thing, in audio purist terms is a nightmare.

Additionally, the SMPS1200 boasts an advanced overcurrent protection mechanism that, during a temporary overload, restricts the output current.

You measure the dv/dt across the resonant capacitor? The 'other thread' on the FTC trying to tramp down on bullshit claims may apply here.

[1] Obvs I know nothing but knowing nothing and despite its other quirks, legs dry out, I would go for a soft switching phase modulated bridge.
 
Yet you stated that your very recent tests showed power as being 700 watts at 4 ohms with 1% distortion

The very recent test was to also confirm the shutdown issue observed by Stereophile was not normal (just like the IMD). Was not an official power spec test.

That's why I used non-specific value ranges (over 700, under 1%)
 
Perhaps @restorer-john can correct me, because he's had a much wider range of devices on the bench than I have or @SIY , but I seem to recall throughout history that most domestic power amplifiers have non-regulated supplies feeding the output, current-delivery stage. This is why recovery from impulse is a useful test for showing PSU lag etc.

Absolutely you are correct. Sure, some regulated supply amplifiers, both conventional and switched mode supply based, but the vast majority unregulated (for the output stage).

A slew of switched mode supplies were implemented in the 80s by many of the big manufacturers to reduce size and weight, particularly when slim-line designs were popular.

Funny, I repaired one in my collection where the output stage was driven by a switched mode supply and the driver stage run from a conventional transformer/regulated supply. The SMPS had exploded (caps etc) and made a real mess. Luckily is was inside a sealed aluminium self contained box inside the amp.
 
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Final testing? So you haven't run a full power sweep yet? You didn't test and characterise the amp before the power and other numbers went on the website and it went on sale?
No, we did, back when we had the AP. But doing new round of testing since the Stereophile article because......well, self-explanatory.
 
So you did run power tests. Did they meet the spec you published? Can you post them?
Feel free to dig back through the official thread in the Dealer section. You had already seen the graphs in question and decided to look elsewhere.
 
For that matter, would suspect that Purifi uses a bench supply that would show the best amplifier performance rather than be potentially limited by a specific vendor's supply.
They use a PSU of adequate capacity for spec'ing their own modules :)

This is clear from the datasheet plots. And also the reason why datasheet specs cannot be automatically used as OEM amp specs.
Fully agree - the PSU used in the unit must be what is used to derive all published specs of the unit as a whole - up to and including limits in the lowest octave IMNSHO...
 
This is exactly one of the questions that should be asked. I pointed out years ago that a NAD M23/M33, for example, has a significantly larger PSU for the smaller 1ET400A.
 
This is exactly one of the questions that should be asked. I pointed out years ago that a NAD M23/M33, for example, has a significantly larger PSU for the smaller 1ET400A.
I don't know about the models you mention,but one of the first NADs using Purifi nearly gave up the ghost trying to drive loud (with 5 people in a big-ish room) the small 3-way ATCs (50 must be) some 3-4 years ago.
I would test before buy in such case.
 
What happened? Did it recover or was it permanently damaged?
The room started smelling electronics and it was really hot to touch.
It didn't die,no.
It went for service after that though,the smell was enough to scare the owner.
 
I don't know about the models you mention,but one of the first NADs using Purifi nearly gave up the ghost trying to drive loud (with 5 people in a big-ish room) the small 3-way ATCs (50 must be) some 3-4 years ago.
I would test before buy in such case.
A 150-200wpc integrated could not drive 85dB/1M 9" 3-ways to venue-esq levels? Shocked... KH150's have 245W ea and will certainly not fill a large room w/o stressing hard, and even have a higher max rated SPL than those ATC's... I'm sure that amp was being abused for the sake of trying to get somewhere that system was not designed to go...

But I will agree with you - I'm not a NAD fanboi after a horrible experience with the T175 and T175HD (lost over $3K on that), and another NAD integrated that died. But they do seem to use over-designed PSU's - I guess that's something to be praised.
 
A 150-200wpc integrated could not drive 85dB/1M 9" 3-ways to venue-esq levels? Shocked... KH150's have 245W ea and will certainly not fill a large room w/o stressing hard, and even have a higher max rated SPL than those ATC's... I'm sure that amp was being abused for the sake of trying to get somewhere that system was not designed to go...

But I will agree with you - I'm not a NAD fanboi after a horrible experience with the T175 and T175HD (lost over $3K on that), and another NAD integrated that died. But they do seem to use over-designed PSU's - I guess that's something to be praised.
I think that the added problem apart from level,distance,etc at such listening are people.
The more in a room,the worst.Of course is about levels for that too,but...
 
A 150-200wpc integrated could not drive 85dB/1M 9" 3-ways to venue-esq levels? Shocked... KH150's have 245W ea and will certainly not fill a large room w/o stressing hard, and even have a higher max rated SPL than those ATC's... I'm sure that amp was being abused for the sake of trying to get somewhere that system was not designed to go...

But I will agree with you - I'm not a NAD fanboi after a horrible experience with the T175 and T175HD (lost over $3K on that), and another NAD integrated that died. But they do seem to use over-designed PSU's - I guess that's something to be praised.
NAD has always taken a slightly different approach. While they haven't always gotten everything perfect, my experience with them has been positive in terms of delivering a lot of power for the price. That said, I don’t have any experience with their newer class-D models.
 
NAD has always taken a slightly different approach. While they haven't always gotten everything perfect, my experience with them has been positive in terms of delivering a lot of power for the price. That said, I don’t have any experience with their newer class-D models.
Yes,their old budget one must be a benchmark along with the small Yamaha's for entry level audio back in the day.
And they are stil around I think,one can't miss their ugly case :p
 
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