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Old 5th February 2018, 10:24 PM   #31
MrMagic is offline MrMagic  Greece
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You are a moving target MarcelvdG and thus we are going in circles... Click the image to open in full size.
Unless you become SPECific about what you really mean, we cannot arrive to a common conclusion. Even a discussion, needs to follow some specs actually.

So, let's take the most negative meaning of specs: forced constraints.

You can't attempt anything worthwhile without forcing some constraints, ie specifying a minimum goal or specs. Even when you decide to design or play a game, you have to set some strict constraints that shouldn't be possible to violate, in order to make the game challenging and thus, fun. Without a challenge, there is simply NO fun in anything. Period.

If some of my specs are "flexible", that's due to a strategy defined by other specs (you can consider it an algorithm) and like me, a company might follow the same strategy or alghrithm when attempting something novel, or extremely optimized via R&D way beyond what's available, so in that case, both me and them cannot pre-define all the final specs precisely -doing so while in uncharted waters, would be ridiculous.

For example, the THD <0.01% and 1400V I had set for my ES amp on the other thread, were definitely "specs" (constraints), as were the following:

-DC,
-Direct drive (which means a dual supply requirement),
-ultra low noise (the minimum I can achieve)
-deep optimization (perfectionism)
-high reliability
-reasonable cost
-competitive to the best consumer products

All are currently satisfied (with ultra low noise, and THD hitting a record) except voltage which I had to lower to 1300V due to component limitations, by giving priority to "high reliability" and "reasonable cost" specs / constraints.

Now my new goal is to make the prototype keep them, specifically THD < 1ppm and I've set some new real-life noise-related goals that require more R&D. That, aside the additional feature-specs (like embedding a DAC) that also require more work.

Bottom line: Strict constraining specs are required for anything worthwhile, even for fun, or hobby. Being flexible with some of the specs, might be a strategy, not an indication of being loose and having more fun. If you are too loose, you are not self-desciplined and that reduces your efficiency and your ability to accomplish a worthwhile goal, considerably, and finally long-term satisfaction and enjoyment.

Last edited by MrMagic; 5th February 2018 at 10:37 PM.
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Old 6th February 2018, 05:02 AM   #32
MarcelvdG is offline MarcelvdG  Netherlands
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I would love to give you some practical examples, but that would violate NDAs, so I have to stick with hypothetical cases.

Suppose you would have overconstrained one parameter while forgetting another one, one that's far more important during normal use. As a hobbyist you would probably find that out during the design phase and adjust your requirements accordingly. In a professional context, that's far more difficult.

A typical example are the audio DAC chips I mentioned before. Suppose a customer puts constraints on chip area and dynamic range, forgets headroom, and makes the constraints on chip area and dynamic range so tight that you can only just meet them without any headroom. The only way you can meet the customer's requirements is to make a DAC that has no headroom and is therefore not suitable for playing music. Of course you could try to convince the customer to reduce the dynamic range and add headroom, but their marketers would probably not accept that, because the customer's customers only look at dynamic range anyway.

In the end you would spend months to develop a crap product with impressive-looking datasheet numbers that's unsuitable for playing music, and probably get quite frustrated about it, especially if you like your job.
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Old 6th February 2018, 07:39 AM   #33
traderbam is offline traderbam  Europe
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Marcel makes sense to me.
Sometimes specmanship is a bad thing. Audio circuits should aim to convince a human that they are hearing music. The very best measurement device is a human. Everything else is a proxy measure. A proxy is of questionable dependability so focusing exclusively on proxies is risky if not downright misleading.
For example, the THD proxy that is often top of the list is very poorly correlated. So why judge a design by it? The DAC spec examples illustrate how choosing the wrong spec can lead to designs with great specs and poor sound.

When I buy a piece of audio gear I don’t bring a laboratory to the showroom with me and let it decide what I should buy. Of course not. I audition. I take a lot of time. I compare using different music. Before I go to the shop I read magazine reviews to confirm a number of things but mainly the audition by the reviewer.

So which diyaudio project a person chooses may be driven by all sorts of things. For the particular criteria of “playing music convincingly” I don’t think a long list of proxy specs is going to be very helpful.
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Last edited by traderbam; 6th February 2018 at 08:04 AM.
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Old 6th February 2018, 11:29 AM   #34
traderbam is offline traderbam  Europe
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Originally Posted by MarcelvdG View Post
In the end you would spend months to develop a crap product with impressive-looking datasheet numbers that's unsuitable for playing music, and probably get quite frustrated about it, especially if you like your job.
Unless you are a DAC/amp supplier to Apple!
<rant>I just don't believe how poor music is on my 6S and its even worse on the external DAC dongle they provide for newer, jack-castrated phones. These are really expensive devices and why doesn't Apple ask someone who knows what they are talking about to sort this out? Instead, we get a $1000+ phone with a highly complex face recognition system that nobody wants and Beats quality audio.
<end rant>
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Old 6th February 2018, 02:12 PM   #35
MrMagic is offline MrMagic  Greece
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Originally Posted by MarcelvdG View Post
Suppose you would have overconstrained one parameter while forgetting another one
. . . . . . . . . . . .
Suppose a customer puts constraints on chip area and dynamic range, forgets headroom, and makes the constraints on chip area and dynamic range so tight that you can only just meet them without any headroom.
That's a classical case of a logical leap, or fallacy.
You blame the scientific / technical institution of using specifications, and the companies and DIYers who take specs seriously, just because some "customers" and companies abuse that institution, trying to cheat people with various tricks.

It's like considering science evil, or banning it altogether, just because some fraudsters use science to cheat the public with pseudo-scientific evidence.
It doesn't work like that, which is why I've insisted a couple of times in our debate-Odyssey that this is irrelevant, or OT.

Abusement, fraud and cheating, exists in every sector you can imagine. That doesn't mean anything, there will always be a percentage of parasitic and pro-chaotic behavior, like the noise you see on a FFT graph. No system is 100% perfect on this universe.

It's up to us to look for the fine print in datasheets or spec lists and check in depth what we read, in order to avoid being deceived, 99.9% of the time.

Personally, if I discover that a company systematically tries to cheat me, I'll ban that company completely, and most likely I will share my experience with other people in an emphatic way.

Such companies don't have a bright future, or no future at all.
It's on the fundamental principles of marketing the requirement of a great product, and a policy that respects the customer, to ensure a marketing success and start using marketing in the first place.


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The very best measurement device is a human. Everything else is a proxy measure. A proxy is of questionable dependability so focusing exclusively on proxies is risky if not downright misleading.
The problem is that we humans are highly emotional beings, prone to various psychological effects like placebo, and extremely high sensor illusions (visual, acoustical, etc), let alone the differences in personal training, experience and knowledge, therefore our judgement is a mixture of too many unknown and unmeasurable parameters.

So in order to have a good judgement of performance using our vulnerable sensors and perceptions, highly sophisticated tests have to be designed and used. Just going into a shop is rather hopeless to judge subtle specs like those for an amplifier. You will have a better chance with loudspeakers and headphones though where the differences are huge.


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Originally Posted by traderbam View Post
For example, the THD proxy that is often top of the list is very poorly correlated. So why judge a design by it?
I would love to hear why "THD is very poorly correlated", assuming all else equal of course. I'm all ears.


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Originally Posted by traderbam View Post
<rant>I just don't believe how poor music is on my 6S and its even worse on the external DAC dongle they provide for newer, jack-castrated phones. These are really expensive devices and why doesn't Apple ask someone who knows what they are talking about to sort this out? Instead, we get a $1000+ phone with a highly complex face recognition system that nobody wants and Beats quality audio.
<end rant>
So you're missing Steve, right?

Last edited by MrMagic; 6th February 2018 at 02:21 PM.
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Old 6th February 2018, 02:23 PM   #36
scottjoplin is offline scottjoplin  Wales
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The problem is that we humans are highly emotional beings, prone to various psychological effects like placebo, and extremely high sensor illusions (visual, acoustical, etc)
It would be a bigger problem if we weren't
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Old 6th February 2018, 02:27 PM   #37
matze is offline matze  Europe
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Originally Posted by MrMagic View Post
... Just going into a shop is rather hopeless to judge subtle specs like those for an amplifier. ...
You should really accept that many people simply make different experience, if you replace "spec" by something like "sonic character".
(This does not mean that the whole undertaking you propose is useless.)

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Old 6th February 2018, 03:34 PM   #38
traderbam is offline traderbam  Europe
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So in order to have a good judgement of performance using our vulnerable sensors and perceptions, highly sophisticated tests have to be designed and used.
Our auditory systems have evolved over millions of years. Have some self-respect.

Quote:
I would love to hear why "THD is very poorly correlated", assuming all else equal of course. I'm all ears.
Speaker THD.

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So you're missing Steve, right?
No. I'm missing decent sound quality in my phone.
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Old 6th February 2018, 03:47 PM   #39
traderbam is offline traderbam  Europe
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Originally Posted by scottjoplin View Post
It would be a bigger problem if we weren't
Exactly.

To all: The appliance of science is one thing. Measuring the wrong thing because it is convenient and claiming it is right is another. That's just dumb and lazy. And saying that humans are not qualified to judge music is...well, bizarre.
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Old 6th February 2018, 08:09 PM   #40
MrMagic is offline MrMagic  Greece
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Quote:
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Quote:
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So in order to have a good judgement of performance using our vulnerable sensors and perceptions, highly sophisticated tests have to be designed and used.
Our auditory systems have evolved over millions of years. Have some self-respect.
Our auditory systems have evolved, but our perception when doing audio tests, is the sum of several illusions, plus distortion is more apparent in specific sound combinations (content-dependent), which is why you need to listen with a proper test method in order to exclude all other conflicting factors, and focus on the most revealing parts.

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For example, the THD proxy that is often top of the list is very poorly correlated. So why judge a design by it?
I would love to hear why "THD is very poorly correlated", assuming all else equal of course. I'm all ears.
Speaker THD.
We were talking about amplifiers, THD is not on the top of the list in loudspeaker specs, it hardly exists in most specs, and I've already stated previously that there is no problem with loudspeakers because the differences are huge.

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saying that humans are not qualified to judge music is...well, bizarre.
Nobody said that, and we are not talking about judging music, we are talking about judging subtle audio reproduction differences. Whatever test you can imagine, needs a proper test environment and methodology. That's basic knowledge.

Last edited by MrMagic; 6th February 2018 at 08:15 PM.
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