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Review and Measurements of Purifi 1ET400A Amplifier

jdhiro

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I'm hoping for something like this as well. I already have the NC2K and it sounds fantastic, but there's something to be said for being able to hit reference levels with zero theoretical audible distortion and noise. I guess designing a perfect amplifier with unlimited headroom isn't that easy. :)

I am curious, did you ever compare your NC2K side by side with lesser Hypex, and if so, did you notice a headroom difference?
 

nerdoldnerdith

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I am curious, did you ever compare your NC2K side by side with lesser Hypex, and if so, did you notice a headroom difference?
I am driving Revel Salon2's. Before I was driving them with Purifi 1ET400A's, which were clipping at 3dB below reference. Now I am driving them with the NC2K's, and the headroom difference is very noticeable when you are listening loud enough. However, that level is indeed quite loud (100+dB). I am not using the full capability of the amp, which I think would probably fry the speakers.

Ideally I would like an amp that does 1500W into 4 ohms and hits 106dB SINAD at full power. The NC2K is only perfectly transparent up up 70W, and the 1ET400A is perfectly transparent up to about 250W. Most of the low distortion is wasted with my speakers.
 

David_M

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Finally! Exactly what I was waiting for!

Purifi 1ET7040SA
Output Power: 950W(2Ω), 500W(4Ω), 250(8WΩ)
Output Current: ~40A
THD+N: <0.00035% @ 200W, 4Ω, 1kHz
Dynamic Range: ~129 dB(A)
Output Noise: ~14µV(A)
Gain: 13dB
Output Impedance: <13µΩ @ 1kHz
Efficiency: 94% @ 500W, 4Ω, 1kHz
Idle losses (outpt stage): 2.8 W

The output power ratings in 8/4/2 ohms are at 1% THD+N level (based on the power graphs --> -40dB THD+N), which is defined as the audible clipping point, hence NOT MUSICAL at this power level. Not sure what their rated power in these impedances is, since a given THD+N level is never specified like many other audio amplifier manufacturers have been doing for decades do. Is the specified THDN 0.001% or 0.01% or 0.1% or some other value? Purify needs to pick one and then state the output powers at this spec,
 
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Matias

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The output power ratings in 8/4/2 ohms are at 1% THD+N level (based on the power graphs --> -40dB THD+N), which is defined as the audible clipping point, hence NOT MUSICAL at this power level. Not sure what their rated power in these impedances is, since a given THD+N level is never specified like many other audio amplifier manufacturers have been doing for decades do. Is the specified THDN 0.001% or 0.01% or 0.1% or some other value? Purify needs to pick one and then state the output powers at this spec,
THD+N at 1% is the (low) standard everyone uses. Or check their curves and pick the point you like best, but some amplifiers don't have a clear knee to pick a point from.
 

nerdoldnerdith

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The companies with nothing to hide give THD+N at rated power and post measurements to boot. That is why some companies rate their amplifiers so conservatively.
 

David_M

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THD+N at 1% is the (low) standard everyone uses. Or check their curves and pick the point you like best, but some amplifiers don't have a clear knee to pick a point from.

Yeah, but they can't have customers determine their own power based on these curves. It's highly unconventional and not FTC compliant anyways, which specs THD+N for 20Hz-20KHz for a given impedance.
 

David_M

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Are you guys starting a conspirationist story based on the supposed lack of detailed information contained in a not yet published document from which somebody leaked a few data?
Asking for a friend...

Not really ... same specmanship is done by Purifi on its current lines of products, unfortunately.
 

David_M

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This is such a bad take, they give so much more information than a typical manufacturer.

Michael
That's definitely true ... but that info must be useful to a potential customer so that they may be able to compare amp choices in a fair manner. Current info confuses the customer as one could say my amp runs at 0.0001% at 100W but another says, their same amp runs at 450W at 1% into 4 ohms.

Purifi should pick a power level that satisfies the distortion levels they want as per FTC specs.
 

boXem | audio

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That's definitely true ... but that info must be useful to a potential customer so that they may be able to compare amp choices in a fair manner. Current info confuses the customer as one could say my amp runs at 0.0001% at 100W but another says, their same amp runs at 450W at 1% into 4 ohms.

Purifi should pick a power level that satisfies the distortion levels they want as per FTC specs.
What customer are you talking about? DIYer? Manufacturer?
 

VintageFlanker

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output power ratings in 8/4/2 ohms are at 1% THD+N level (based on the power graphs --> -40dB THD+N), which is defined as the audible clipping point, hence NOT MUSICAL at this power level.
:rolleyes:
Just about any amp manufacturer (or audio press) consider "Max Power" that way: up to 1%THD+N. Some are even state this as "continuous"... And many (many) times this value is overestimated. Not with manufacturers such as Hypex or Purifi: these specs often match with tier party measurements. And no, they won't rate their max power at 0.0001%, they have to give an apple to apple comparaison with the rest of the industry.

Besides, this is certainly suitable for musical content. Unless your music is a fixed monotone at 0dBFS. You won't notice extremely rare peaks at 1% (assuming you're listening at max volume)
 
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mk1classic

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As long as they provide the THD vs Watt curves for different loads, frequencies etc we are OK. It doesn't matter what they indicate as MAX we do usually not play music continues at these levels.

I'm happy as long as we stay away from this kind of Watt indications...:rolleyes::D
 

tmtomh

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Folks, we've been over this a hundred times. Hypex and Purifi both give topline power ratings that are misleading - but they also provide detailed specs and measurements/datasheets that tell the full story.

So yes. I'd love to see Hypex and Purifi replace the "400" that's all over their module names and the "headline" wpc rating with "250" to more accurately reflect their real-world, full-frequency performance. (And of course to replace "500" with something like "300" and "250" with something like "150," and so on.)

But other than that, they're not hiding anything, they're not lying, and they're certainly not doing anything that purveyors of other amp topologies don't also do.
 

David_M

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As long as they provide the THD vs Watt curves for different loads, frequencies etc we are OK. It doesn't matter what they indicate as MAX we do usually not play music continues at these levels.

I'm happy as long as we stay away from this kind of Watt indications...:rolleyes::D

Power curves are fine ... but utterly useless and confusing to the average John and Jane Doe, who can't read or understand them. They go to their local audio shop (or big box stores) and see's comparatively priced amp A rated at 100W (all channels driven, 20Hz-20KHz)) and amp B (Purify based) rated at 450W rated at @ 1KHz only! Which one will they choose, especially by John Doe who says MORE POWER = BETTER POWER (tho he might be right)?
 

David_M

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I can think of one situation why Purifi specs the way they do, via the power curves. They leave it to the end-user/manufacturer to determine the power and distortion specs of their end product. I could spec 100W/Ch @ 0.0001% THD+N ... another vendor could spec 250W/Ch @ 0.01% THD+N ... and yet another could spec 350W/Ch @ 0.1% THD+N ... and they would be ALL CORRECT if they are using the same module. In hindsight, this is a clever and flexible way Purifi gives them this kind of flexibility.
 

JohnYang1997

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I can think of one situation why Purifi specs the way they do, via the power curves. They leave it to the end-user/manufacturer to determine the power and distortion specs of their end product. I could spec 100W/Ch @ 0.0001% THD+N ... another vendor could spec 250W/Ch @ 0.01% THD+N ... and yet another could spec 350W/Ch @ 0.1% THD+N ... and they would be ALL CORRECT if they are using the same module. In hindsight, this is a clever and flexible way Purifi gives them this kind of flexibility.
This has always been the case. Except you seem to be so stucked at FTC regulation.

To quote from a TI's document:
'There are a few standards that describe the power rating of an audio amplifier. The Federal Trade
Commission (FTC) establishes fair advertisement practices for home audio power ratings. This is
described in the FTC document 63FR37233, 16 CFR, Chapter 1, Part 432. Another standard is the
Electronic Industries Association (EIA) SE-101-A. For the car audio industry, some manufacturers accept the Consumer Electronics Association CEA-2006-A standard. It defines how the amplifier should be tested
for power and signal distortion.'

So there are different standards and regulations to be used. FTC is mainly targeting at "advertisement" instead of actually specifying the amplifier. So that no false information is used. The well known erroneous Watts RMS unit is from this regulation.

I have yet find documentation on SE-101-A. From my source it's mentioned as being old and non-active.

CEA-2006-A is relatively newest and most widely accepted standard for standardized testing. The well known 1% power rating, A-weighted SNR etc are from this standard.
There are more information on this site if you don't want to buy official document. http://rftech.custhelp.com/app/answers/detail/a_id/199/~/cta-2006-(cea-2006)-amplifier-power-standards

To be fair, the final solution is just to publish as detailed measurements and tests as possible. There's only so much information that you can squeeze in one sentence. Don't say average joe or layman can't understand it. Then why do we expect them to understand anything at all. All data is published it's up to the customer to learn how to read the specification and decide what's suitable for them.
 

tmtomh

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This has always been the case.

I agree - and I would emphasize this important point, and add that the main difference is simply that with Hypex and Purifi, the OEM's datasheet is very well publicized, even moreso than the specs that might be published by most of the vendors who use the modules in finished products. With traditional AB amps marketed mostly by big name brands, we never pay any attention to how the OEM who makes the transistors, modules, or "packs" etc might spec them.

So we're seeing the "sausage being made" in terms of specs more than we traditionally have. This is a good thing, but it does lead some folks <cough>restorer-john</cough> to get fixated on FTC vs module datasheet.
 
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