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Review and Measurements of Purifi 1ET400A Amplifier

maty

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Off topic

I was about to comment it but before I commented in another forum (Audiocircle/Power conditioning) about a new product designed by Aleksandar, aka ATL Hi-Fi.

You have gone ahead, but I wanted to highlight another paragraph.

End off topic


Rod Elliott says:

http://sound.whsites.net/articles/balanced-2.htm

[ The bridge is most sensitive to small fractional impedance changes in one of its arms when all arms have the same impedance [ 7 ]. It is least sensitive when upper and lower arms have widely differing impedances. For example, if the lower arms have infinite impedance, no voltage difference can be developed across the line, regardless of the mismatch severity in upper arm impedances. A similar scenario occurs if the upper arms have zero impedance. Therefore, we can minimise CMRR degradation due to normal component tolerances by making common-mode impedances very low at one end of the line and very high at the other [ 8 ]. The output impedances of virtually all real line drivers are determined by series resistors (and often coupling capacitors) that typically have ±5% tolerances. Therefore, typical line drivers can have output impedance imbalances in the vicinity of 10 ohms. The common-mode input impedances of conventional line receivers is in the 10 k to 50 k ohm range, making their CMRR exquisitely sensitive to normal component tolerances in line drivers. For example, the CMRR of the widely used SSM-2141 will degrade some 25 dB with only a 1 ohm imbalance in the line driver.

Line receivers using input transformers (or the InGenius® IC discussed later) are essentially unaffected by imbalances as high as several hundred ohms because their common-mode input impedances are around 50 M ohms - over 1000 times that of conventional 'active' receivers... ]
 
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pirad

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Maty,
Rod Elliott also wrote there:
"For many applications, the use of balanced interconnects is simply not needed at all. In general, a home hi-fi needs balanced interconnects like a fish needs a bicycle, but someone, somewhere, decided that balanced connections 'sound better', but not because of noise reduction."

Do you work in pro audio or you are going to buy for your fish a bicycle?
 

maty

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That is another discussion, balanced vs unbalanced.

Before buying the kit I will wait for others to verify if besides a spectacular sound (which I do not doubt) is capable of transmitting emotion with certain recordings.

Just now, the hybrid SACD: https://www.discogs.com/Fairground-Attraction-The-First-Of-A-Million-Kisses/release/13170861

In his day I followed the development of the famous ODAC of NwAvGuy from the beginning. It took me months to buy mine once it was available. Which, by the way, sounds a lot better now than when he came into my house, but that is another story.

Let us wait for Bruno's reply.
 
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I don't think this discussion is leading anywhere.

Is Rod Elliot some kind of saint? Because while his statement is most likely true for most scenarios, putting it in words like his makes it look kind of unprofessional. I doubt he can prove that "someone, somewhere, decided that balanced connections 'sound better', but not because of noise reduction", so why would he include this bold statement? Again, it might very well be true, but it's unprofessional and far from being objective to phrase it like this.
 

amirm

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Is Rod Elliot some kind of saint?
He writes exceptionally well done articles on audio/amplifier design. He really thinks through stuff and often debunks common myths. So yes, it is an authority that can be called upon.
 

Xulonn

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I don't. It's fascinating
It may be fascinating to those who enjoy cringeworthy displays of Dunning-Krugerism, but I don't enjoy watching people make fools of themselves in public by refusing to learn when offered excellent free advice.

There is a huge amount of technical audio information here that is free for the asking. People like me who choose to continue to learn over their lifetimes, can see the debate over answers to their questions between qualified experts when the science is not settled. Anything that is truly controversial will be challenged and will likely have to run through a gamut of honest criticism and differences of opinion here at to ASR.

I find it a bit sad when people initially appear to be sincere in their comments and suggestions, but chose to remain ill-informed, and refuse to study information suggested by real, actual experts in the field. Even as an audio enthusiast for 60 years - fairly knowledgeable, but not a technical expert - I learn something here nearly every day. And I have been participating at internet audio forums since the 1990's.

I am more fascinated when someone arrives here at ASR, posts from a perspective of misinformation, asks intelligent questions, and then displays the ability to interact with and learn from experts. That's probably why I liked school - from kindergarten through an undergraduate degree program at respected university. Because learning can be fun - and challenging. And for many of us who are seniors, mental challenges help to prevent dementia.
 
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He writes exceptionally well done articles on audio/amplifier design. He really thinks through stuff and often debunks common myths. So yes, it is an authority that can be called upon.
I think my question makes more sense if seen in context.

I don't disagree with what he says about balanced interconnections, I just think the way he does so is not really that entertaining (to me) or beneficial to a discussion. He can't prove the claim that someone decided balanced sounds better and that it has been a thing ever since or something like that. The vast majority of Hi-Fi gear I have come across does not have balanced In- or Outputs due to various reasons, reality much proves his point already. No need to get unobjective and make bold claims.

But I guess different rules apply when one is trying to debunk common myths, after all you have to get attention somehow.
 

Fred Jacquot

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It may be fascinating to those who enjoy cringeworthy displays of Dunning-Krugerism, but I don't enjoy watching people make fools of themselves in public by refusing to learn when offered excellent free advice.

There is a huge amount of technical audio information here that is free for the asking. People like me who choose to continue to learn over their lifetimes, can see the debate over answers to their questions between qualified experts when the science is not settled. Anything that is truly controversial will be challenged and will likely have to run through a gamut of honest criticism and differences of opinion here at to ASR.

I find it a bit sad when people initially appear to be sincere in their comments and suggestions, but chose to remain ill-informed, and refuse to study information suggested by real, actual experts in the field. Even as an audio enthusiast for 60 years - fairly knowledgeable, but not a technical expert - I learn something here nearly every day. And I have been participating at internet audio forums since the 1990's.

I am more fascinated when someone arrives here at ASR, posts from a perspective of misinformation, asks intelligent questions, and then displays the ability to interact with and learn from experts. That's probably why I liked school - from kindergarten through an undergraduate degree program at respected university. Because learning can be fun - and challenging. And for many of us who are seniors, mental challenges help to prevent dementia.
I fully agree with what you wrote. Seeing people refusing to learn is quite sad.

But in this case, I am also learning. About humans.
What kind of mental mechanism brings a random forum user to explain to the designer of renowned analog amplifiers how to sort out his resistors?

Dunning-Kruger can't explain everything, there is something else here.
 
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I fully agree with what you wrote. Seeing people refusing to learn is quite sad.

But in this case, I am also learning. About humans.
What kind of mental mechanism brings a random forum user to explain to the designer of renowned analog amplifiers how to sort out his resistors?

Dunning-Kruger can't explain everything, there is something else here.
Hi, random user here. I can think of several mechanisms that would trigger someone like myself to explain things. :) And I'd be happy to have an actual dialogue with someone esteemed. As far as renowned goes they too seem to have a tendency to appreciate certain feedback.
As per your specific example of sorting resistors my OCD would likely top the list, but it shouldn't surprise you that I've also got reasons that may seem sensible, at least to me.
I have only skimmed the posts but as far as I can tell it is possible that the renowned designer chose sub par components intentionally, again. Or it doesn't really matter all that much. After all it's not supposed to be a refined and polished product. It is also possible that this has already explained, but to be honest a lot is a little above my head here.

What ever the case it seems there was a question about it, and a rationale behind that. Not a case of some random user explaining to god how to run the world.

I too can see how strange humans are.. I suppose all I have to do is look into a mirror. But hey, thats just me..
 

Fred Jacquot

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Hi, random user here. I can think of several mechanisms that would trigger someone like myself to explain things. :) And I'd be happy to have an actual dialogue with someone esteemed. As far as renowned goes they too seem to have a tendency to appreciate certain feedback.
As per your specific example of sorting resistors my OCD would likely top the list, but it shouldn't surprise you that I've also got reasons that may seem sensible, at least to me.
I have only skimmed the posts but as far as I can tell it is possible that the renowned designer chose sub par components intentionally, again. Or it doesn't really matter all that much. After all it's not supposed to be a refined and polished product. It is also possible that this has already explained, but to be honest a lot is a little above my head here.

What ever the case it seems there was a question about it, and a rationale behind that. Not a case of some random user explaining to god how to run the world.

I too can see how strange humans are.. I suppose all I have to do is look into a mirror. But hey, thats just me..
Hello random user. It's random user writing. I am sorry if you felt my post was aggressive.
I will unfortunately have to disagree with you.
No, on scientific subjects, all opinion don't have the same value. When experts talk and you are not an expert, well, you listen and ask questions when something is not clear for you. If a majority of experts agrees, they may be right.
Second, since you did not dig into all the exchanges, you may have missed that there is NO rationale behind this, just an obsession for external noise developed during the last weeks that is spreading in all threads about speaker amplifiers. Strangely not in DAC or headphone amps threads. It came again here, everybody tried to explain that CMRR from an internal module was anecdotical, Bruno explained it too, and also explained why. Result: @maty doesn't care and suggests improving the accuracy of some resistors.
If you spend your brand new company's money for useless things, do you think you deserve your job? I don't.
But I may be strange too ;)
 
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Hello random user. It's random user writing. I am sorry if you felt my post was aggressive.
Yes I did. (Edit: Removed some text here after googling Dunning-Kruger :) I do, however, appreciate your apologetic concern.

Judging by your comment it seems there is an interwebbs thing, I had no clue, and in that light I appreciate that folks in the know have taken the time to explain, yet again. Apparently some random users only visit one forum.

Yes, you're strange, no doubt.
 
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maty

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About Rod Elliott, three days ago:

Rod Elliott saves the day again!
https://www.diyaudio.com/forums/solid-state/340303-rod-elliott-saves-day.html

He is changing site and web address:

=> https://sound-au.com/

Please Note: The sound.whsites.net site will be closed permanently some time before July 2020. Please update your bookmarks to refer to sound-au.com (this site) and ensure that you visit here before using the old site. Despite 18 years of use, Westhost doesn't appear to value their long-term customers, so we will be parting ways. No new material will be added to the 'old' site, and redirects for individual pages will be installed over the next few months. My apologies for the change (again, but I can't influence the decision that would have seen the old site closed anyway).
 

maty

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From time to time I check: https://www.google.com/search?q=Purifi+1ET400A+Amplifier

Today, at third page, a video from two days ago. Bavmike/Mivera Audio: Janis Joplin, Summertime.


Welll, the sound... It is not the theme that I would have chosen.

Summertime.

* Janis Joplin - Greatest Hits + 18 Essential Songs (1995), CD, Columbia/Sony, US

Theme: DR10

* Janis Joplin - In Concert (1972), Vinyl, Columbia 1978, US

Theme: DR10

* Janis Joplin - O.S.T. 'Janis' and Early Performances (1975), Vinyl, Columbia, US

Theme: DR12
 
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maty

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If Amirm still has the kit I could pass him several themes, well known, with a sensational recording quality and so upload his own video, with better microphone and tracks.

In a new thread: Impressions of Purifi 1ET400 Kit amplifier.

Of course, with the prior consent of Purifi Audio.
 
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Hi All,
Lars has gone on vacation so it’ll be just me today. It may make for a less entertaining read than the Q&A we did for Audiophilestyle, but I still hope it’ll be worth it.
Thank you Bruno. It is interesting to read, and also much appreciated, even though I don't understand most of the details. While there is a lot to dissect I decided to not leave you hanging indefinitely and to say a something. A something something :)

For instance, I learnt a new word, Shyster. I feel a little struck but I don't work in sales so I don't take it personally. However, if you have an opening in sales I can sell anyting I believe in :) Understanding the product naturally makes me sell even better, but if I have no love for it I guess I'd have to hook up with Danish wellfare. .. How'd that go; I don't want no well fare, I just want to fare well? Not that I am fishing for a sales job or anything. Mostly having some kind of online monologue amongst the mighty.

We’re well and truly off on a tangent here but anyhow: it comes in nowhere.
Incoming office joke. Oh noe, I was beat to the pun.

If you take two signals (say, square waves, or sharp transients) of which one is delayed by 1us compared to the other, and then you band-limit both to 20kHz you'll find that the 1us time difference is still there and perfectly visible on a scope as a horizontal offset between the two filtered signals.

A correctly implemented sampling system, that is one with a LPF before sampling and one after reproduction, is indistinguishable from the band-limiting filters alone, by any means, whether by frequency or time domain testing (can’t stress that enough). We have the Sampling Theorem to thank for that. So with the sampler in place this small delay remains perfectly intact. In fact an AD/DA can resolve the time of arrival of a transients within a much tinier fraction of a sampling period, limited only by SNR (the signal theoretical pendant of Heisenberg’s Uncertainty Principle). IIRC some listeners can, under careful listening conditions, detect inter-channel time delays on the order of 2us (in the form of a minute left-right shift of the stereo image). This is perfectly within the ability of even 44/16 to reproduce. An ability to discern microsecond scale timing does not mean, and has never meant, that you need 500kHz sampling. Sadly, precisely this misconception is wilfully being repeated over and over by some shysters on the “high res” front.
Is there a week course I can take somewhere? (I have an idea!) I don't get it and I don't feel I can provide a sensible question to clarify what I am supposed to get here. :( But since I am likely completely wrong in my conception that I'd need an amp capable to rock short duration signal space something something it doesn't really matter all that much that I comprehend your response. I mean, since I have to start from start again anyways. But yeah, it looks very odd to me that I am so wrong about this that it doesnt even belong in a thread about amps.

I was also directed to a thread here by @Soniclife and @somebodyelse
that to some extent also addresses this and I'm kinda pushing through it, but it'll probably be another week. Specially considereing that there's also a thread about rockin female vocalists.

So I am learning new words again. thx :thumbsupsmiley:

Brilliance and diligence in equal measure. We love hippies so long as they have a sense of humour about it.
Yes, it was all meant in good spirit. Alcohol over here is not that shabby. Seriously though, hippies are the best (second only to punks off course) and you perfectly dot the i on this one. One big happy family..

First time I read brilliance and diligence in equal measure I thought thats just too perfect. Awesome. You have a good team helping you answer these questions. Bet you all had a great laugh :) Then I thought of my current super, who has little to do with any of all this (even though he works from 7 to 20 and is a hippie at heart). And then I realized I was confusing diligense with perserverance. It took a while too so you might imagine what schemes of perserverance I was picturing in order to get hired at best sound .dk Not that I am fishing or anything. And that hole in the fence wasn't me probing the grounds either.

Where was I? Ahh, rambling. Here we are :) I googled diligence and realized two things, hard work it is not. Its a fantastic little word, with a surprising amount of religious recognition. Also, my previously highly regarded "due diligence" was thrown out the window since it is apparenty defined as the minimum requirement to avoid beeing negligent. Wow right?

Lets cut to the bark then, I can do religious all day, all we need is some bling, water vapor, a chair and a bearded guy. The brilliance is the easy part and I'd dial it down to hallelujah levels. So if you're on the watch for security personell (I don't have any formal training in securoty) or anything (high priest, sales, qa, RND) you name it, feel free to let me know. And I'm not, I mean, I know you're not hiring, Im just saying. Maybe I know a hippie who would love to help. It be like me helping you help yourself. You'd naturally owe me one Kenobi, but it'd be my pleasure.

If you dont mind a slight slide before we end; any more details on the drivers? What else comes with them? Do I need to lego my own cross overs? Will they fit my old wife-dissapproval speaker cabinets? (I dont have a wife, I meant the cabinets) And speaking of, since they're addressing some particular issues, would it make sense to have a post amp adjuster circuit thingy that kind of tells the amp how to drive the speakers? I don't mean taped pebbles now, more along auto adjusting to 4 or 8 ohm loads, but adressing more than ballpark impedance. I mean since the characteristics of particular speakers are so distinct perhaps a matching circuit of sorts could make sense?

anyways, having been a member on this forum for about two weeks it's now my devious honor to say thanks on behalf of the community and to let you know we love you long time (I am kidding, we just have to say that to everyone)

Kind regards,
Nikke
 

Bruno Putzeys

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Hi All,

It seems there were only a handful of questions left. I’ll start with the ones that I’d apparently missed the first time round.

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.
That would certainly be the plan. The design brief for the SMPS is universal mains with PFC, more or less regulated output (to maximise power output from the amp) and low idle losses. It’s quite a job. I should note that Hypex has made clear improvements in the idle losses in their SMPS a few years ago.

Is 1ET400A vs nc400 an audible improvement soundwise? If so, in some certain way, like better high frequencies? Would you think it’d be audible for only driving 15” woofers in closed boxes actively in the range 25-650Hz in my system?
The specs have improved over the whole spectrum so you wouldn’t expect any audible improvements to be restricted only to the top end. That said, I’d be massively skeptical if anyone told me he hears a difference in a subwoofer application. I certainly wouldn’t rush to upgrade amps in a sub.

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?
We’d need to see the measurements of those class AB amps if we want to stand any chance of speculating fruitfully.

Is gain variable like on nc400 with r141?
That is the middle resistor of the buffer stage. The 1ET400A has no built in buffer. The structure of the buffer on the I/O board is the same though so you can indeed change the gain there in the same way.

Which is your favourite music record, the one you never get tired of hearing?
Oh goodness, my Desert Islands Discs. Wish Lars were sitting here. He’d rattle off a bunch of classical recordings on the spot. When I was younger I could re-listen a small number of albums forever. More out of economic necessity than artistic sense mind you. Blame streaming for the ADD that I as a music lover have caught since. I’ve become a novelty seeker and don’t often play the same albums over. On the other hand, most of those albums from my youth would cause me a lot of embarrassment if I were to name them.

Things from my old collection I can still listen to:
  • Johannes Kerkorrel en die Gereformeerde Bluesband, Eet Kreef (it helps to understand Afrikaans though, and remember what SA looked like in the 80’s)
  • The Waterboys, Fisherman’s Blues
  • Jean-Michel-Jarre, Equinoxe
A few contemporary albums that spring to mind that I’ve recently played more than 5 times and still like:
  • Nils Frahm, All Melody (And the rest. Frahm is one of the few people I’d declare myself a fan of)
  • Public Broadcasting Service, Race for Space
The obligatory classical album that’ll be the one saved when the desert island floods (UK readers may have to explain that to the rest):
  • Pieter Wispelwey and Dejan Lazic, Complete Sonatas and Variations for Piano and Cello.
And finally a long shot, 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? :)
I have never toyed with any of the ESS chips, mostly because I felt that if I wanted to have that sort of SNR I might just as well do a discrete circuit and solve distortion and birdies too. But I’ve used a lot of AKM stuff in a variety of products and have yet to be disappointed.

Does the amp emit any on/off thump 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?
A thump is what you get when there is a DC offset that suddenly gets turned off along with the amp. The NC400 had a fully discrete buffer which had the potential for developing DC offsets, especially when driven with a high impedance (e.g. an AC coupled output). That’s why it had trim pots. The 1ET400A has a DC offset of less than 10mV (is on the web site) which doesn’t normally produce a noticeable thump, so it doesn’t need trimming. But of course if you decide to build a discrete buffer, you might need to make the input stage trimmable.

Aside from a DC thump, there is always the potential for a small turn-on and turn-off click because of the sudden start or stop of the PWM signal. We try to minimize that by letting the microcontroller take charge of the output stage the first few microseconds. As it stands you need to put your ear very close to the tweeter before you notice the click. I guess that’s a good enough result.

Will it be possible to install speakon connectors directly on the connector PCB, in place of the binding posts?
I put in four large through hole pads that you can solder wires into so it should be trivially easy to connect a speakon connector with wire terminals. Brownie points for requesting speakon, which I consider the only serious speaker connector around. Sadly the rest of the hi fi market doesn’t seem to care (or prefers to care about other things).

Is it possible to set a different gain for each module of the stereo combo?
Sure, the 2 channels are independent after all. But the place to do so would be in the buffer, the gain of the amp module itself is fixed.

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 :D
I think you are referring to the current drive used in the Kii and Grimm speakers to reduce the hysteresis distortion in the legacy drivers that are used there.

The Purifi woofer doesn’t rely on anything on the amplifier end for its performance, because we don’t want to force people to buy both drivers and electronics from us (or give the impression that we do). But neither would it make sense to give people instructions how to improve the performance of their non-Purifi drivers. Or give the impression that doing so brings them anywhere close to what our driver does. Current drive cleans up the mid-band like a treat but low frequency performance does not improve.

Besides, we sell amplifiers and drivers. If we were to start selling complete solutions, what value is there to be added by the manufacturer that buys our stuff and puts it in a box? It’s bad enough as it is with amplifier companies fearing the inevitable question “so what justifies the price of your amp compared to a DIY build”.

Oh, almost forgot: When? How much? (for the DIY market) :D
I mentioned it already but for completeness: webshop to open somewhere in the autumn. Prices competitive (i.e. low enough for other parties to start re-thinking their DIY price settings).

still a lot of people said:
(still about CMRR)
Folks, CMRR is spec’ed as 60dB or better, and the resistor tolerances are chosen accordingly (working this out is left as an exercise for the reader). It is a matter of statistics that if you have a grab bag of x% resistors and you take two at random, they are quite likely to be matched within a fraction of x%. So there’s nothing unusual about a module that suddenly has a CMRR of 20dB better than spec. In fact, it would take a lot of effort not to have the occasional “way better than spec” exemplar.

As I read Maty’s first remark after my post, he said that if people are going to charge a mint for an input buffer to go with the 1ET400A, the least they could do is provide measurable evidence that it actually adds value. I wouldn’t necessarily pick CMRR specifically as the item they have to improve but I sympathise massively with the sentiment.

Sadly that is not how the free market works. It’s very much buyer beware: if the buyer doesn’t request evidence of added value before handing over money, the seller has no reason to provide such evidence. What’s great about a forum like this one is that it’s basically about collecting that evidence whether the seller wants to or not. But it’s only people who realise they need consumer protection that’ll seek it.

Especially the high end audio market has successfully bamboozled customers into thinking value lies in esoteric materials and parts (which after all is easy to do, easy to communicate and easy to make a margin on) rather than in improving actual performance by engineering (which is hard to do, hard to get across and only turns a profit if enough people see the point). Starting a company like Purifi is a way bigger gamble than starting an “accessories” company. It relies on enough people questioning the status quo.

[Am I] completely wrong in my conception that I'd need an amp capable to rock short duration signal space something something?
If you replay two identical musical signals over two identical speakers in a good room, it sounds like it’s coming from a point exactly in the middle between the speakers. If you delay the right hand signal by 2us, that will sound like the image has now moved left by a few millimetres. Under ideal circumstances you might be able to train yourself to detect that. When people claim that the human ear is sensitive to time scales in the low microseconds, this is the experiment they are referring to. The important thing is that you do not need “fast” signals to do that. It works fine with Red Book CD audio. It might even work with lower bandwidths. So, your ear’s ability to hear tiny time shifts does not require a high bandwidth, not in the signal and not in the electronics.

But now consider this: do you think anyone can hear the difference between
1: A 10V, 1us long impulse
2: Two 5V, 1us long impulses 20us apart (slightly EQ’d for the pedants among us)

Clearly not. The two would sound exactly the same. Human listeners do not need equipment with with the sort of time resolution (=bandwidth) that could resolve the second case as two separate pulses.

The ability to discern short delays between left and right channels have nothing to do with time resolution.

I would like to stress the shyster epithet was not aimed at you. I reserve the term for people who follow and understand this completely and still claim that you need to invent a new (preferably proprietary and specifically their) digital audio format based on the minimum audible interchannel delay, knowing full well that the argument is flawed.

I’m not sure whether I should read your questions regarding employment as half-serious or not, so for the sake of completeness: you can always send a CV.

Any more details on the drivers? What else comes with them? Do I need to lego my own cross overs? Will they fit my old wife-dissapproval speaker cabinets? (I dont have a wife, I meant the cabinets) And speaking of, since they're addressing some particular issues, would it make sense to have a post amp adjuster circuit thingy that kind of tells the amp how to drive the speakers?
You get the driver. For the rest you’ll have to, well, DIY. Should you feel unsure of your speaker design skills, it’s probably best until some of the more seasoned folk in the community have tried their hand and put their designs online. The driver is designed to be easy to work with for designers of normal passive speakers, so no specific adaptations on the amplifier side are required.

Right, I’ll be off on holidays for the whole of August. Should any pertinent questions turn up, maybe someone can drop me a pm. That would save me a fair bit of scrolling in September.

Cheers!

Bruno
 

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May 30, 2019
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North Wales, UK
I mentioned it already but for completeness: webshop to open somewhere in the autumn. Prices competitive (i.e. low enough for other par
ties to start re-thinking their DIY price settings).
This means I really should wait and see rather than buying something else now... OK then maybe I'll get that shed built in which to build a new amp. Use of the dining table doesn't go down that well with my wife.
 
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