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Review and Measurements of Purifi 1ET400A Amplifier

kuba-phase

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SINAD is one ranking. Just noise and distortion at 1Khz. Which serves to separate the chaff from the wheat. However, above a certain SINAD level (SINAD >= 96Db), two amps would sound indistinguishable from each other if used in their ideal load conditions, i.e. if the load is such that they both can sound at a reasonable level and without load-dependent frequency variations. In other words, they are both transparent, and two transparent amps cannot have a different sound (with the above conditions of use caveat). However, amplifiers differ in many other aspects, and some have a flat frequency response with difficult loads (such as speakers with low impedance, esp. in the bass region, and far from being purely resistive), whereas others show significant variations, which also color the sound.

Some of the measurements taken by Amir show some of these aspects of amplifiers (and other electronic components) as well as some other aspects, but also lack measurements with speakers (i.e. real world loads) and the only listening test are done with some really crappy loudspeakers (sorry, Amir, but this is true!). Do not let this detract from the service he is doing. In fact he is providing much more information than just the SINAD, and even though he himself indulges a bit in the notoriety his raking gives him and this site, I think it is a disservice to his work to focus too much in this value.

Above a certain SINAD level, which many amplifiers nowadays reach also at very reasonable prices, other factors should lead your choice of amplifier. And Fred told you perhaps the most important ones – which also depend on the speakers you are planing to drive.
It is a real pleasure to learn from someone who knows the subject (I think ;) and wants to share his knowledge. Thank You. OK, now I know more about the subject, I wish it was easier. But going further, maybe I should modify my question. Which amplifier should I buy? I understand that there are many factors and it is impossible in practice to predict how a particular device will behave with specific speakers. You wrote I should focus as well on other parameters, but I'm wory that I simple not able. I believe (and I think it is good word) that perfect amplifier is device amplifying signal without any distortion. Knowing that, and since we know that SINAD is important, and frequency response vs load and max power vs load are even much more important, maybe there are some kind of "safe choices"? Maybe my opinion is wrong, but I thought that Hypex nCore and Purifi are the best ones on the market, the best in every aspekt.
 

Julf

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I thought that Hypex nCore and Purifi are the best ones on the market, the best in every aspekt.

They pretty much are. What is hard to say is if you would hear any improvement compared to your current amp.
 

mocenigo

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"? Maybe my opinion is wrong, but I thought that Hypex nCore and Purifi are the best ones on the market, the best in every aspekt.

Well, as others also have commented, they pretty much are. But not only because of their SINAD. They have an incredibly flat and load independent frequency response, and plenty of power too (headroom is always good). High damping factor. Almost no IMD. No noise. They are very efficient. Other amps like the AHB2 have higher SINAD, but most NCore or Purifi solutions are less expensive. Unless you have Apogee Scintillas, they can drive any speaker you throw at them.

So, yeah, they pretty much are, except for corner use cases.

Roberto
 

kuba-phase

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They pretty much are. What is hard to say is if you would hear any improvement compared to your current amp.
Well, as others also have commented, they pretty much are. But not only because of their SINAD. They have an incredibly flat and load independent frequency response, and plenty of power too (headroom is always good). High damping factor. Almost no IMD. No noise. They are very efficient. Other amps like the AHB2 have higher SINAD, but most NCore or Purifi solutions are less expensive. Unless you have Apogee Scintillas, they can drive any speaker you throw at them.

So, yeah, they pretty much are, except for corner use cases.

Roberto
Thank you. So the conclusion is simple. Going to nCore/Purifi department will be a trip called "I have the best amp", but not necessarily my ears will notice it. Got it. I would like to take this opportunity to ask You one more thing. Previously, I had an IcePower 1200AS2 power amplifier. In terms of sound quality, it seems to me it sound the same as the VMV A2, but with one big difference. The 1200AS2 hummed through my speakers (tweeters actually). The noise wasn't that loud of course, but there is no doubt that it was much louder than in the VMV A2. It was regular noise, not mains 50Hz hum etc. Just regular noise, like in any other "regular" amp. Even when I connected 1200AS2 only to the mains and loudspeakers (DAC disconnected) it hummed quite loudly compared to VMV A2. In the VMV A2 I have dead silence, and on the same speakers. Can it be concluded from the 1200AS2 specification that this hum is so audible? Reading the parameters, I got the impression that despite the high efficiency of my speakers, it should still be unnoticeable. 1200AS2 as well has noise from itself, from device (trafo buzz) but I'm aware of that and not asking about it.
 

normanu

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I had a 1200AS2 which was dead silent, I don't think it is the amp.
But I was not so impressed by the "sound", I came from a Electrocompaniet AW3x120M and the Icepower was considerably more dull.
 

kuba-phase

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I had a 1200AS2 which was dead silent, I don't think it is the amp.
But I was not so impressed by the "sound", I came from a Electrocompaniet AW3x120M and the Icepower was considerably more dull.
My 1200AS2 was dead silent as well on my previous speakers. But the speakers efficiency was very low. Visaton LaBelle - 81 dB (1 W/1 m). What are Your speakers?
 

Kelims

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Thank you. So the conclusion is simple. Going to nCore/Purifi department will be a trip called "I have the best amp", but not necessarily my ears will notice it. Got it. I would like to take this opportunity to ask You one more thing. Previously, I had an IcePower 1200AS2 power amplifier. In terms of sound quality, it seems to me it sound the same as the VMV A2, but with one big difference. The 1200AS2 hummed through my speakers (tweeters actually). The noise wasn't that loud of course, but there is no doubt that it was much louder than in the VMV A2. It was regular noise, not mains 50Hz hum etc. Just regular noise, like in any other "regular" amp. Even when I connected 1200AS2 only to the mains and loudspeakers (DAC disconnected) it hummed quite loudly compared to VMV A2. In the VMV A2 I have dead silence, and on the same speakers. Can it be concluded from the 1200AS2 specification that this hum is so audible? Reading the parameters, I got the impression that despite the high efficiency of my speakers, it should still be unnoticeable. 1200AS2 as well has noise from itself, from device (trafo buzz) but I'm aware of that and not asking about it.
I bought 2 x Hypex fa 252 and now I use it to passive speakers ( necessary Bi Amping) with this I have a quality amplifier DAC and room correction. I know I am not able to use all the features of the Hypex but the price performance ratio is the best on the market.
 

mocenigo

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Thank you. So the conclusion is simple. Going to nCore/Purifi department will be a trip called "I have the best amp", but not necessarily my ears will notice it. Got it. I would like to take this opportunity to ask You one more thing. Previously, I had an IcePower 1200AS2 power amplifier. In terms of sound quality, it seems to me it sound the same as the VMV A2, but with one big difference. The 1200AS2 hummed through my speakers (tweeters actually). The noise wasn't that loud of course, but there is no doubt that it was much louder than in the VMV A2. It was regular noise, not mains 50Hz hum etc. Just regular noise, like in any other "regular" amp. Even when I connected 1200AS2 only to the mains and loudspeakers (DAC disconnected) it hummed quite loudly compared to VMV A2. In the VMV A2 I have dead silence, and on the same speakers. Can it be concluded from the 1200AS2 specification that this hum is so audible? Reading the parameters, I got the impression that despite the high efficiency of my speakers, it should still be unnoticeable. 1200AS2 as well has noise from itself, from device (trafo buzz) but I'm aware of that and not asking about it.

So you mean that the 1200AS2 was hissing. I know people using that module with Avantgarde Duo and Klipschhorn loudspeakers - very high sensitivity loudspeakers, yet it is dead silent (except for the slightly humming transformer). Maybe your amp was defective or assembled improperly.
 

Labjr

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So you mean that the 1200AS2 was hissing. I know people using that module with Avantgarde Duo and Klipschhorn loudspeakers - very high sensitivity loudspeakers, yet it is dead silent (except for the slightly humming transformer). Maybe your amp was defective or assembled improperly.
I wonder how those high sensitivity speakers sound with Class D?
 

Julf

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I wonder how Class D amps sound with those high sensitivity speakers?

Amp class is pretty much irrelevant from that perspective (only exception is a badly designed A/B amp - if there is crossover distortion, it is more prominent with a high sensitivity speaker).
 

mk1classic

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I have a collection of Anaview AMS0100 amps and a Purifi EVAL1 amplifier on my speaker setup.
I heard no hiss from my speakers when running passiv crossovers, but now when I run the speaker with a cheap "PA" DSP based active crossover then I can hear a weak hiss from the midrange horn and the super tweeter. So for me it comes from the preamp. I have tweaked the gain structure to limit the hiss now.
 

mocenigo

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I wonder how those high sensitivity speakers sound with Class D?

Apparently very well. My speakers are a 3 way build with active subwoofer part (one per channel) and a passive xover for the top two ways. The sensitivity of the bass to treble part is around 97.5 Db/W/m and I use a Purifi based amp to drive them. Everything sounds glorious.
 

phoenixdogfan

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The only caveat about the Eigentact lies in the pitfalls of doing this DIY. I did it that way, and couldn't get it to work b/c it had some defect in the HYPEX SMPS which caused it to fail under load. I sent the SMPS back to Hypex 3 times and they "fixed" it, sent it back, and it failed every time with the very first power up. Also wound up sending the Eval 1 back to Purifi, they verified it was working perfectly, so it was not the problem. Bought entirely new wiring from Ghent which also did not solve the problem. Eventually Rick Sykora volunteered to look at the entire amp, was able to troubleshoot it, and determine the problem was with the aux power in the SMPS. He got it fixed, and it's been working perfectly ever since.

The moral of the story is to buy this from an assembler such as VTV which sells it cheaper than you can DIY it because of the OEM discounts it receives. Ultimately I paid $400 on freight and repair fees on top of the $1200 for the kit parts which drove my price to around $1600 for my DIY. VTV sells it for around $1000 and they have a two year warranty on the unit--so a no brainer.

Having gotten everything straightened out, I bypass the pre-gain stage and drive it with an Octo DAC 8 Pro with the two channels devoted to the Purifi custom set to 10 VRMS by Octo. As far as I'm concerned, the set up is as good as I'm ever likely to need to drive any passive speaker I'll ever want to pair with it.
 
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rdenney

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...But going further, maybe I should modify my question. Which amplifier should I buy?

These days, amp selection is a lot easier that it used to be. Here are the usual requirements:

1. Sufficiently low distortion such that the distortion is effectively inaudible while listening to music.

2. Sufficiently flat frequency response that the only need I'll have for EQ is to correct speakers and room issues, and the only reason I'll want tone controls is to season particular recordings to my taste.

3. Both 1 and 2 into the speakers I'm likely to own.

4. Sufficient power to satisfy all my listening use cases while still fulfilling 1-3.

5. Looks good.

6. Fits in the space I have for it.

7. Reliable and repairable.

8. Efficient (which means different things to different people).

9. Integrates with my system (such as: sufficient gain to provide a sensitivity reachable by whatever I feed into it, allows a balanced inputs if my system provides it, allows unbalanced inputs otherwise, etc.)

10. Demonstrates something about me that I want to demonstrate (this could be wealth, discernment, brand, location of manufacturer...whatever), and gives me the backstory and ownership experience I want.

11. I can afford it.

There are not very good amps that don't fulfill the first three requirements. The fourth requirement for me means: Too much power may not be necessary but too little power is the most likely weakness to cause an audible effect. So, for me, sufficient power is the first and most important specification parameter to choose.

Requirement 9 is knowable and measurable and there is a right answer or not. With an active preamp that puts out the usual 10+ volts, even low-gain amps will be fine. Passive preamps with input sources at 2 volts (unbalanced) will often need more gain in the amp than some provide.

Requirement 7 requires research, and Requirement 6 is what it is.

Requirements 5 and 10 are intangible, but should not be confused with measurable requirements. It's okay to want a fancy brand just because it's fancy, just know what you are and aren't buying.

Then comes Requirement 11.

With the exceptions of Requirements 5 and 10, the good Class D amps that use nCore and Purifi modules fulfill all these requirements for most folks. An amp like the Benchmark does that plus adds some cachet that pushes into Requirement 10, but is a bit less accessible with respect to Requirement 11. 10 and 11 are often inverse because 10 is so driven by the prestige of having spent a lot.

With nCore, it's just a matter of deciding how much power you need--all options are available from one source or another.

With Purifi, power isn't as much as the biggest nCore amps, but it's enough for most use cases. But the Purifi more abundantly fulfills the first two requirements.

With the Benchmark, power is a bit lower still, but still enough for most folks and most use cases. And the Benchmark is the state of the art in low distortion.

If you generally want peaks under 100 dB SPL within 8 or 10 feet of reasonably efficient speakers, power may not be much of an issue. For bigger spaces or higher listening levels, or with inefficient speakers, more thought will be needed.

So, it's possible these days to get stereo amps among the best of those measured for prices ranging from a few hundred dollars to a few thousand dollars. Pick the one you can afford, and focus on more important stuff.

But if Requirements 4 and 10 are important to you, there are also quite good choices that have all those stories. You may need to bring your checkbook, but even some good vintage amps are not expensive but still fulfill most requirements (except Requirement 6 and 8--older amps are not particularly efficient compared to what is available now, but then neither are higher-end amps than the Benchmark).

Rick "amps are generally a solved problem" Denney
 

Matias

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With Purifi, power isn't as much as the biggest nCore amps, but it's enough for most use cases. But the Purifi more abundantly fulfills the first two requirements.
The new high power module from Purifi has been on pre-sale in limited quantities for manufacturers. Soon we will have an official launch and available everywhere, but of course it will be more expensive than the 1ET400A, let's see how much more.
 

kuba-phase

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I bought 2 x Hypex fa 252 and now I use it to passive speakers ( necessary Bi Amping) with this I have a quality amplifier DAC and room correction. I know I am not able to use all the features of the Hypex but the price performance ratio is the best on the market.
Interesting. What are Your speakers? I assume your speakers are 2 or 3 way, so why didn't You go full active (for 3 way 2xFA253) ?
 
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This is a review and detailed measurements of the Purifi 1ET400A Class-D amplifier module. Company was kind enough to send me a complete, assembled kit consisting of two modules, power supply and case, ready to go. They have not disclosed the cost of the unit. Modules will be available to DIY channel in Q4 of 2019.

As cases go, the prototype unit came in an attractive one:


A touch of color on the lid goes a long way to break the monotony of DIY aluminum cases. Someone should take this case, put two giant VU meters in the front and make me happy! :)

Here is a quick teardown:


A single Hypex SMPS1200 is used to power both channels. That feeds two 1ET400A amplifier modules.

A single "Amp Connector Board" feeds both channels using balanced input through an optional gain stage of 13 dB. Here is more detail from documentation on the features of this EVM board:

View attachment 28849

I was pleased to see high-quality Rubycon capacitors used in the amplifier modules:
View attachment 28850

The power supply seems like the stock Hypex SMPS1200:
View attachment 28851

It is remarkable that a high-performance amplifier could be built in such a small enclosure with so few subcomponents.

In use, the evaluation unit would barely get warmer above room temperature. Heat dissipation is simply not an issue here. You could easily put these amps in an enclosed cabinet and not worry.

Note that the main offering here is the 1ET400A. The Amp Connector board is offered as convenience. In that regard, I tested the amplifier with and without the extra gain that the connector board provides. Alas, I wish there was something in between. You get full power with as little as 1.5 volt with the extra gain but need 11+ volts without it. I like to see manufacturers build a gain stage that produces full power at 4 volt which we routinely get out of source products (e.g. DACs).

Amplifier Audio Measurements
As provided, the extra gain stage was active producing this dashboard view at 4 ohm producing 5 watts:
View attachment 28852

Focusing on FFT spectrum of a 1 kHz tone, we see stunningly low distortion product. 2nd Harmonic is barely visible which may actually be the contributions from my source signal. The third harmonic hovers around -130 dB which again, is almost at the limit of what we can measure. Given the ear's 116 dB or so dynamic range, you are assured zero audibility of these distortion products.

THD+N and hence SINAD (signal over noise and distortion) is substantially lower though at 104 dB. Since THD+N is sum of distortion products and noise (+N), the latter is the culprit here. We can see this reflected in SNR measurements:

View attachment 28853

As you see on the left, our noise contributions is essentially what we see for SINAD. Fortunately at full power (right), performance shoots way up to fantastic level of 123 dB.

We can do better though by disabling the pre-gain stage:
View attachment 28854

We gain 4 dB in SINAD resulting this summary ranking:
View attachment 28857

The Benchmark in its low gain mode maintains the championship status still but the 1ET400A gives it serious competition here.

SNR naturally improves with lower gain:

View attachment 28858

Drilling into the distortion (with pre-gain active) we see the vanishing harmonic distortion more plainly:
View attachment 28859

Power is everything in amplifiers so let's see how we do with 4 ohm load:
View attachment 28862

The tables are turned and the 1ET400A produces 257 watts of exceptionally clean power. More could be had if I had run this test with finer resolution and/or allowed the distortion to climb more.

We see the effect of lower gain with reduction of noise at lower power levels although even with the extra grain stage, we are talking very quiet here.

Switching to 8 ohm, the results are similar:

View attachment 28863

Notice the big difference between a commercial amplifier (QSC DAC2422). They have more brute-force power but nowhere as clean as the 1ET400A amplifier module.

Intermodulation distortion versus power gives us another shot at analyzing distortion, this time what is in audio band:
View attachment 28864

The Benchmark AHB2 maintains its less noisy baseline but as we reach full power, the 1ET400A catches up to it and keeps going with more power.

Distortion+noise versus power and frequency yields this (with pre-gain stage on):

View attachment 28865

I was surprised to see the rise in distortion with frequency. I had hoped that the super high gain-bandwidth of the 1ET400A would do away with this. Not an audible concern though as the distortion products here are all in ultrasonic range.

I ran this test multiple times, tuning the input voltage. This eventually upset the amp and caused it to shut down when producing 274 watts into 4 ohm before our sweep completed (in green). Documentation clearly states that extra cooling is needed for continuous power.

The Benchmark AHB2 does a lot better since it has much cleaner ultrasonic spectrum:

index.php



Frequency response is exceptionally flat for a class-d amplifier:

View attachment 28866

The output filters in class-d amps can cause variations as we get close to 20 kHz but we see none of that here. Response smoothly rolls off. At 50 kHz, we are down 1 dB.

Crosstalk using my non-optimal setup is still exceptional:
View attachment 28867

I had to pull up the graph to show its crosstalk at 1 kHz. The 1ET400A is that good!

EDIT: here is the broadband spectrum of a 1 kHz tone:
View attachment 28895

We have our switching frequency around 500 Khz and its harmonic at 1 Megahertz. Otherwise pretty clean.

Conclusions
It was just a few years ago that people scuffed at class-D amps not being very clean or good for audiophile use. How the situation has changed. First with Hypex modules and now with the Purifi 1ET400A. Audiophile myths are shattered with use of large amount of feedback and high bandwidth to produce an amplifier which brings transparency to anything you throw at it.

Importantly, the 1ET400A does all of this while producing a ton of power and staying cool and efficient to boot.

There is a subjective aspect to measurements that doesn't come across in the graphs. When I run these tests with switching amplifiers, I often watch the analyzer struggle to get reliable reading, or there are jumps and glitches in measurements. None of that was here. The amplifier basically acted like a traditional class AB amplifier. Indeed, I measured it with and without my AES-17 40 kHz filter and the analyzer was happy both ways. This is when I know there is quality engineering that has gone into design of this amplifier.

Overall, it is my pleasure to strongly recommend the Purifi 1ET400A to DIY and OEM manufacturers.

-------------
As always, questions, comments, recommendations, etc. are welcome.

The pink panthers can be pretty lazy at times. I asked them to help clean up the lab and they rolled their eyes and went back to sleep! So I need to hire a housekeeper to keep the walk way clean to my test station. Please donate generously as the hourly rate can be high for such work:

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upgrading your membership here though Paypal (https://audiosciencereview.com/foru...eview-and-measurements.2164/page-3#post-59054).
just curious what's on the back side of 1et400a amp board, could you please post a detailed photo of the 400a back side?
 

mk1classic

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