Review and Measurements of Purifi 1ET400A Amplifier

[amirm]

Also there is a typo in the conclusion where you write "hyex" rather than hypex.

Thanks. Fixed.

 

[Soniclife]

Basically if you blast the speaker with high enough level ultasonic signals (well over 70dBSPL) that are still within its response range (24kHz+28kHz), some IMD can just be detected in the absence of any other in band music signals.

So well designed class D that has its switching frequency well past where tweeters work are not affected at all by this, as expected.

 

[Matias]

Don't forget questions for Bruno.

 

[Murrayp]

I've wondered where timing comes in this wide bandwidth discussion. As a Tact RCS owner some years ago I could adjust Left/Right timing with 10us resolution using my remote control. I felt I could hear a change with only 10-20us timing difference, but certainly with 30us change . I see Wilson Audio stating that timing errors of 15us are audible (advt Aug 2019 Stereophile). My hearing was never good and rolls of now below 10kHz. How is it that we can detect such short timing differences when our basic bandwidth is much more limited? If it is a real or recognised effect, Is there perhaps any way that such detection ability might be affected for better or worse by wide bandwidth noise/amplification? Is there a second processing going on in the brain that handles timing separately (the tiger is coming from precisely over there, so I escape this opposite direction) to the frequency? I understand sight processing for subconscious reactions like catching, is handled differently to normal vision and one can sometimes still catch without being able to see, with certain brain damage. Same for the ear perhaps? And might that explain out of normal hearing bandwidth sensitivities not explained by frequency sensitivity. In other words might this explain why someone might prefer an amplifier with wider bandwidth than otherwise explainable, or be bothered by another with substantial hf content?
I've tried to be careful not to make any statements of audio fact here - just what I think I hear - please be gentle with me (this time ) M

 

[Soniclife]

I've wondered where timing comes in this wide bandwidth discussion. As a Tact RCS owner some years ago I could adjust Left/Right timing with 10us resolution using my remote control. I felt I could hear a change with only 10-20us timing difference, but certainly with 30us change . I see Wilson Audio stating that timing errors of 15us are audible (advt Aug 2019 Stereophile). My hearing was never good and rolls of now below 10kHz. How is it that we can detect such short timing differences when our basic bandwidth is much more limited? If it is a real or recognised effect, Is there perhaps any way that such detection ability might be affected for better or worse by wide bandwidth noise/amplification? Is there a second processing going on in the brain that handles timing separately (the tiger is coming from precisely over there, so I escape this opposite direction) to the frequency? I understand sight processing for subconscious reactions like catching, is handled differently to normal vision and one can sometimes still catch without being able to see, with certain brain damage. Same for the ear perhaps? And might that explain out of normal hearing bandwidth sensitivities not explained by frequency sensitivity. In other words might this explain why someone might prefer an amplifier with wider bandwidth than otherwise explainable, or be bothered by another with substantial hf content?
I've tried to be careful not to make any statements of audio fact here - just what I think I hear - please be gentle with me (this time ) M

See the following thread for more about this than you want to know.
https://www.audiosciencereview.com/...qa-creator-bob-stuart-answers-questions.7623/
Best to not corrupt this thread with more of that.

 

[Frank Dernie]

Sending you a private message. Subjective opinions are not allowed here - and no, I did not do a blind test. So if you want to regard my observations as worthless, that is fine.

Why do you write this? This is the second post of yours I have read today claiming this. Certainly unsubstantiated non level matched impressions are known to be pointless here but “not allowed?” - bollox.
I suppose you must be too new a member to have absorbed the ethos of the place so far but you have brought ridicule on the site by false statement once that I have seen which is completely unfair IME.

 

[renevoorburg]

Dear @Bruno Putzeys ,

It appears to me that modern amplifiers like the Eigentakt, NCore and AHB2 have reached such levels of perfection that, certainly for home use, it doesn't seem to be wise to invest in further improvements, beyond their current state. Would you agree on that? And if so, in what area do you expect most future improvements? Is it in active speakers?

Thank you,
René Voorburg

 

[kn0ppers]

Not trying to answer this question for Bruno, but if I get my hands on some Eigentakt amps, I will most certainly employ a DSP in the signal chain and also invest in some room treatment. It's the reason I like headphones so much: I don't need to worry about the room. I think it was also mentioned in the Interview, but check out Kii Audio. Bruno also is the CTO of the company. They make active speakers with integrated DSP, NCore technology amps and digital inputs (Kii Three). So this might be a hint. I also think the Kii Three is a really cool product.

Without a DSP and/or (preferably and) some acoustic room treatment, I wouldn't say amplifiers this good are a waste (because they are obviously great devices), but they deserve better in my opinion. Call me crazy, but I sit there worrying about my poor amplifier performing at his best, but still not being able to deliver the best performance due to lacking support. Must be frustrating for the poor thing, it could definitely use some help!

On Topic:

I assume the PCB to PCB connectors used on the 1ET400A are identical with the NC500? The NC500 datasheet mentions Chyao Shiunn JS-1107-18x2.

Spoiler: There was something here, but it's irrelevant now

I only found one where I am pretty much sure it is the correct pairing, but it's only listed on Digikey, MOQ 1000 and only on order. It's the Sullins PPPC182LJBN-RC (this is the gold plated variant, there is also a tin plated one I think). Pitch 0,1" (2,54mm), 2 rows, 36 contacts (2x18), female, right-angle, through-hole, PCB-to-PCB connector. I would have imagined availability of this part being much better, after all these connectors are very standard and are also used heavily in PCs etc. . This part surely has to be available somewhere?!

I will edit this post if I find what I am searching for.

Edit: eBay to the rescue.

 

[amirm]

I am starting to mark questions in red as someone wisely started.

 

[boXem]

I am starting to mark questions in red as someone wisely started.

Looks like you missed mine (#140)

 

[miero]

@Bruno Putzeys
Congratulations on your Eigentakt amplifier!
My questions:
1) I guess that Kii will start using new modules instead of NCore in their speakers eventually. If that happens, do you expect there will be a verifiable improvement on the perceived sound quality?
2) On Eigentakt amplifier, what do you consider a "weak point" imposed by the current technology state. For example what would you like to improve after 10 years if technology improves far enough.
3) Can you share on what project are you working now?
Thanks.

 

[amirm]

Looks like you missed mine (#140)

Fixed it.

 

[rajapruk]

Questions to Bruno:

Can you make a SMPS with matching low power consumption?
I have had both Hypex SMPS1200 and SMPS600 with nc400, and I do not like the heat they produce on idle.
If the rationale for going class-d is low power consumption, then I do not get the full picture if the powersupply has high power consumption.

Is 1ET400A vs nc400 a hearable improvement soundwise? If so, in some certain way, like better high frequencies?
Would it be a hearable improvement you think for only driving 15” woofers in closed boxes actively in the range 25-650Hz in my system?

Is gain variable like on nc400 with r141?

I thought the low output impedance was the reason why my nc400 gives so nice ”kick” in my woofers compared to class-AB amps I have had before. But now I read that you don’t give low output impedance any credit to sound quality. What is it then giving me the kick I wonder?! Some kind of compression that is lower?

Which is your favourite music record, the one you never get tired of hearing?

And finally a longshot, do you have any comments about choosing dac with AKM or ESS top-shelf chips? Which of these would you prefer if you had to do a dac with any of them? Or maybe we can state it like which one is least bad in your opinion?

 

[Nikke]

I've wondered where timing comes in this wide bandwidth discussion. As a Tact RCS owner some years ago I could adjust Left/Right timing with 10us resolution using my remote control. I felt I could hear a change with only 10-20us timing difference, but certainly with 30us change . I see Wilson Audio stating that timing errors of 15us are audible (advt Aug 2019 Stereophile). My hearing was never good and rolls of now below 10kHz. How is it that we can detect such short timing differences when our basic bandwidth is much more limited? ) M

I also wonder where the timing resolution comes in. Perhaps it is a technical article worth its own thread, perhaps there is design considerations in the Eigentakt adressing this?

While I keep reading that we are limited to 20kHz, the timing is something I have yet to read anything about. My take is that this is overlooked and possibly because the concept is not understood. Two tones 10uS apart would require an amp that can rock a 100kHz.

See the following thread for more about this than you want to know.
https://www.audiosciencereview.com/...qa-creator-bob-stuart-answers-questions.7623/
Best to not corrupt this thread with more of that.

Corrupt this thread with what, MQA? Is timing resolution discussed in that 40 page long thread?

 

[dkfan9]

Amps/sources and DACs going out to 100Khz and beyond...really??!

The industry is still trying to sell us what we don’t need, or may even harm our playback quality.

Sending my tweeters 20-80KHz signals is as dumb as sending my subwoofers 2-10Hz signals.

Yes, when I was 18 seeing subwoofers flapping in the wind and groaning under distress was fun, but really after ruining the suspensions and bottoming out the voice coils.... well I want that as much as I want more IM distortion in my tweeters.
More lucidly explained in text (and video) than any other:
https://people.xiph.org/~xiphmont/demo/neil-young.html

And 2-10hz is still more beneficial than 20+kHz. Where and when it's there in high quantities (and intended?), it's perceptually significant. A number of folks at AVS have reference level sub 10hz reproduction as a significant system aim.

Unless our systems are also meant to entertain pets. I wonder if high resolution audio could help my brother's recently adopted seperation anxiety ridden dog get through the day a little better. Zoos could better recreate natural environments... hmm I see a business plan forming.

 

[somebodyelse]

Corrupt this thread with what, MQA? Is timing resolution discussed in that 40 page long thread?

Yes, timing resolution is discussed in some detail in that thread.

 

[pos]

Question for @Bruno Putzeys

Nice to have you here!
Kudos for that exciting amp, and thank you for still addressing the DIY market

I second @rajapruk remark regarding a low idle SMPS.
Being able to install the amp in a small enclosure and leave it on 24/7 without worrying about power consumption and/or long term failure would be really nice. After all efficiency at max power is not really representative of the typical use of these amps, which is most probably idle plus a few watts from time to time...

Another question: does the amp emit any on/off thumb or noise? The nc400 is not particularly noisy but it does emit a definite noise on power off.
I see no trims on the amplifier module: how is DC offset handled and what is its typical value?

Will it be possible to install speakon connectors directly on the connector PCB, in place of the binding posts?
Is it possible to set a different gain for each module of the stereo combo?

Last question regarding the future directions you might want to explore with purifi: are you going to tackle the task of bringing transconductance/current drive amplification to the DIY and OEM market? I know your new woofer uses special trick to avoid voltage drive distortion, but having a good offering for a current drive amplifier would still be very nice for reducing distortion in "legacy" cone drivers (and maybe even for your woofer, to a lesser degree) in active filtering scenarios

EDIT: Oh, almost forgot: When? How much? (for the DIY market)

 

[amirm]

Is it possible to set a different gain for each module of the stereo combo?

There are independent jumpers for each channel.

 

[pos]

That is nice, thanks for the confirmation @amirm

 

[tktran303]

Isn’t it funny?

When we had class A or class A/B amps we needed big heat sinks to keep them cool enough to hold and not burn our skin, or worse, not burn out the power transistors. Yet some of us liked to pre-warm our amplifiers, or keep them permanently on for “better sound”, not bothering with the idle power of a few dozen watts.

But as audiophiles we eschewed case fans (even though, beyond a few feet, the fan noise was below the noise floor of the room). So our amplifiers needed to have massive heatsinking added, and along with their heavy toroidal transformers would weigh 20lb or more.
“Reassuringly hefty”, as reviewers would tell us.
Some dealers would even expound that the quality of the amplifier could be determined “just by picking it up”.
And thus over time, an amplifier’s weight became a proxy for its build quality.

For market differentiation, manufacturers decided to give their products a nice shiny chassis.
Why sell an amp in a boring black case made of steel when could package the bits that work in CNC cut block of unobtainium?
Perhaps give it some lights, a nice dial, interesting a/symmetry, a series of numbers or even an obscure name fitting of a Statement or Reference product?
I mean, all the engineering was already done, right? It’s the audio equivalent of giving a facelift, a boob job and a set of new heels to the wholesome girl next door.

Behold! Our 2-man-lift amplifier! It commands the price equal that of an automobile! It’s the super model- it looks smashing, but you won’t be able to take on home. Dang, it must be good...

Along comes class D. It rewrites the rules. It’s compact and efficient. In any reasonable form factor or weight it can provide 3-10dB more amplication (2-10 times more power), which means powering anything from single earphones to outdoor concerts, it can run cooler and thus more reliably. And in the era of rapid development of computing and their associated SMPSs, we can use that knowledge to develop SMPSs for our amplifiers, instead of the old fashioned large heavy toroidal transformers of the 70 and 80s.

In the last decade we’ve had further miniaturisation that brought us tablet computers and smartphones (and their SMPSs.) But unlike all these aforementioned devices, the audio amplifier is one that we don’t need to touch (or even sit close to). Like the disc player, cable box, router/modem or Network Attached Storage- we rarely touch them in common use. Yet as audiophiles we want them our amplifiers to run cool, perhaps be even cooling to the touch! But no, we don’t want heatsinks. And we want to do brave things with our cool running class D- like keep them enclosed in a cabinet, and keep the door closed.

People used to joke that Class A could double as a heater on a cold day.

But now our class D amplifiers are running at “concerning” temperatures of 55C. It seems that overnight we’ve conveniently forgot that the ICs, caps, resistors, diodes, wiring and all other bare components that make up electronics are rated at up to 85C (or higher).

We also want an idle power of a <1 watt, citing environmental or energy security reasons. And yet we are happy to drive our internal combustion engined cars to the local shop and back, or keep the car and A/C running on a cold/hot day when we pop out for a few minutes.

The psyche of the audiophile is very interesting. We seem to want to push the limits...