Here's an analogy for you: it doesn't do any good for my FM receiver to
have a threshold sensitivity of -100dBm if the ambient noise is at -80
dBm.
IOW, if hi-fi amp distortion is below a threshold of audibility, then
it doesn't need to be lower or 0. Moreover, if two amps both have
distortion below a threshold of audibility, it doesn't matter if they
are characteristically different.
Yep, I agree with that too. Of course it leaves the question open of
whether the distortions are audible. In systems where speakers
contribute >1% distortion I'm more inclined to believe it is audible.
I could not call them "hi-fi buffs if they aren't clear regarding what
hi-fi is. Yes, one needs to use caution in reading specifications. It
is likely that most of us in s.e.d are well aware of specsmanship games
played by vendors.
frankly the point here is obvious. 0.2% of even harmonics generally
sounds better than 0.1% of odd. Thus hifi does not simply mean choosing
lowest distortion figure.
The point of a hi-if element is to not "have it sound" at all. To have
it below an audible level is to say it has no sound.
It may be the dream, whether or not it is achieved in reality is
another question.
I could never make the claim that
"different types of distortion sound different" because I am aware of no
evidence that such a statement is true *in general*.
Then you havent tried it. Its too obvious to those of us that have, to
need a study to confirm it. If you dont know the difference between
crossover, clipping and 2nd harmonic, then amp design is presumably not
part of your thing.
The same processing was used, a processing claimed to be superior by LP
fans.
sequence:
1. LP claimed to sound better than CD, for same master source
2. Copy LP to CD
3. listener can't tell the difference between LP and LP copied to CD
4. If #1 and #3 are both true, then it is a logical conclusion
I dont recall what you snipped... not to worry
But perhaps you're saying the technical definition of warm is your 50 Hz
mod system.
No I did not say that. That that is a way to achieve some warmth
clearly does not mean that.
It is? Damn, thought it was rec.food for a minute. Seriously though,
those old debating games tell us nothing.
Since engineers deal in applied science in designing
electronics, a scientific goal definition must be made.
It has been, make it sound as good as possible on x budget.
Otherwise, there is nothing to work with.
snip
Even $50 boom boxes have bass boost and tone controls.
yup
What is the
price range you're looking for?
Lots of kit is of such budgetness as to have inadequate bass response,
eg portable radios, answerphones, various other portables, and budget
goods generally. Also there are space constrained items such as
laptops, mobile phones etc, where again modulation can help.
I dont have a study to quote you, just x years of consistent individual
listener say-sos.
One must question why, if a positive and significant positive listening
response is shown across large populations, why this apparently
inexpensive enhancement is not more commonplace.
Might be lack of knowledge. This is a forum primarily for people who
design these things, how many here are familiar with the tcehnique?
Why isn't there a
"warm" knob on cheap, mid, and high priced gear? It's absence is very
puzzling for such a clear claimed inexpensive enhancement.
That brings in other considerations. Knobs cost money, and 50Hz
modulation is most useful on low-end bottom kit. And deliberate
distortions, while it is known they can improve some music, are frowned
on in better kit. Plus its no longer needed when you've got good bass
anyway.
I would have to see a good study, since there would seem to be no reason
to assume uniformity or even consistancy.
Theres someone who hasnt tried it, and had feedback from others nearby.
It would be like a study to see if cats look different to dogs.
To my knowledge, there is no double-blind evidence that people can
reliably detect the low distortions commonly available in today's hi-fi
power amps.
Curious. I have 2 power amps downstairs, and the difference is obvious.
But the situation is muddier when youve got mutiple distortions present
at once, as is the case with hifis.
Also, the ancedotal evidence, for myself, and the mass of people I know,
is they (and I) can't make quality distinctions between amps with low
distortion content. Thus the lack of scientific evidence by those who
claim ability to detect differences at these low levels, combined with
the anecdotal evidence, leads me to remain skeptical of the claims. I
have no reason to believe it. It *may* be true, but the evidence is
entirely missing.
Indeed, it is not consistent, and the tests not problem free.
Well in my world that wouldn't be so. I would pick the cheapest with
distortion low enough such that I couldn't detect the difference between
the cheapest one and another one that cost $1 more (certeris paribus).
That is, I don't care what the distortion is in either one, if I can't
detect it, and like we learned in ECON101, all decisions are made at the
margin.
That merely begs the question of whether those distortions can be heard
or not.
snip
Basically you are talking about masking. It is similar in a sense to
the lossy compression of mp3. Where some of the sound content
sufficiently masks other content, the content that is masked can be
dispensed with.
This is a processing that you believe sounds nice. That's fine, but it
has little to do with hi-fi.
follow the argument.
To my knowledge, it has not been demonstrated.
Play with some amps. Try modulation.
The problem isn't inadequate bass, per se, it is insufficient power.
no, and not relevant to the point
This is exactly the crux of the matter. You, as best I can tell here,
believe that because distortion is audible and distinguishable at higher
levels, it is audible and distinguishable at lower levels, but just at
some scaled down version.
No I'm not saying that. Thats why those 'ifs' keep cropping up.
There is no scientific reason to presuppose this sort of linear level
transposition of distortion audibility in human hearing. Nature is
replete with examples of non-linear responses (including threshold
effects) by living creatures to environmental phenomena.
no-one said there was a linear relationship
Perhaps the
window response of humans to many phamaceuticals is a good and
well-known example of non-linear response.
In short, there is zero evidence that I am aware of that would
demonstrate that humans do *not* have thresholds in their ability to
hear subtle differences in sounds.
no-one said there wasnt a threshold. We dont know. If there is one,
whether what we hear IRL is above or below it is another question.
The instrument of the ear may indeed
be "sensitive," but that does not equate to infinite sensitivity, nor a
linear response in sensitivity.
indeed, no-one said it did
You're posting to s.e.d. Most know how modulation is performed.
No they dont, we do (mostly) but most people do not.
If they don't, they are probably a bit out of place here.
yes, but not significant. Any account of listeners will need to take
into account those that are not s.e.d. regulars.
This is a compensation nulling (and to some measure imperfect) of
another hi-fi shortcoming. It is not a masking.
Its really not nulling, as resonance produces quite a different output
to the proper response. Bass resonance is a standard deliberate
addition to most speaker systems. There are significant departures from
nulling:
1. The output of a resonant system continues after the excitation has
gone,
2. The output magnitude/time response is unlike the input signal
3. The resonance is triggered by other frequencies as well as the f_res
4. And in the case of lower cost ssytems, the resonance also contains
higher frequencies than f_res as a result of nonlinear cabinet
resonance.
ignorance and unscience permeate most fields. That only means its not
worth looking in the places where one finds no science. It doesnt make
a field invalid.
Well sure. But the fact of life is we only have so many resources.
Basically there is no low-hanging fruit left to pick when it comes to
amplifier distortion.
I would suggest that 50Hz modulation is a low hanging fruit. Few
engineers today pick that one.
And as far as resources, theyre fairly sizeable. A company that
produces a record breaking lower distortion amp can make lots of
marketing mileage from it.
Today's hi-fi fan who commands even a modest
income can get a low distortion and high power amp for fairly low cost
in real dollars.
true, but that does not mean reducing apparent distortion isnt worth
following.
1. Most of us, regardless of wealth, still own minimal cost amplifiers,
eg in portable radios, answerphones etc
2. Ditto for minimum size apps eg laptops, mobile phones.
3. Improving result per dollar of low cost kit is still a valid goal of
engineers: it is in fact a core part of what we do.
This is another way of saying _it isn't worth
pursuing_ in nearly all cases.
The fact that the "audibility question" is not "one we can answer in
this thread," and about a billion others sends us the message of severe
doubt when it comes to valuation of extreme efforts in simply proving or
disproving these marginal claims regarding amplifier distortion in hi-fi
amps. Information can be expensive at times. In this case, the
information is not worth the cost of procurement, as best I've been able
to tell.
Really? Lets look at the last 35 years of commercial hifi amps. They've
come a long way. How? Result per dollar, features, reliability, and
buyer appeal. Result per dollar includes lower levels of distortion for
a given price. This continues to matter, as huge amounts of money are
still involved in portable and budget devices of all sorts, as well as
hifi. Improving return per buck is very valuable - and yes that
includes improvments in distortion figures that have no effect on the
listener, since tech specs are a real-world sales consideration as much
as are blue leds.
If you dont think its relevant, I wonder how competitive a designer you
are.
listeners.
obvious.
Again, this is apparently an assumption of transposition of audibility.
There is no reason to presuppose this that I am aware of.
No such assumption. I think ive said that.
More importantly, there is no reason to assume such a thing is
necessary, for any practical purpose of hi-fi listeners.
Or that it isnt.
If people can't hear it, and to my knowledge they can't, it has been
slayed.
IF. Do you have some evidence that no-one can hear it? Do you have some
evidence that it is a commercial non consideration, regardless of
whether it can be heard? I'd bet my last buck on the belief that the
first company that produces a 0% distortion amp will gain substantial
business as a result. And some extra business if they never even sell
it!
There is no reason to presume a "need" for a zero level of
distortion. That would be a solution in search of a problem.
Uhuh. The problem is money, and its an obvious one. As to whether
todays commercial kit distortions are audible, we really arent sure, so
its an issue.
And even when we do know, and it turns out we cant tell, it will still
be an issue at a sales level. As an example we know printing block
diagrams on amp facias does nothing, but some buyers believed they were
functional latest high tech, and were encouraged to buy. Odd but true.
Obviously. The question for the user is the mix they deem optimal; that
would be balancing the defects as best they can. The designer simply
allows them a measure of choice in determining that mix for the local
situation.
Tell me something. Since we know todays systems are not perfect (one
only need look at speaker specs to see that), and we know that one
distortion can improve a sound with another type, how do you know
whether the type of amp distortion does or does not partially
compensate for real world speaker limitations? We really dont know, so
either way is possible. Why does it matter? Primarily, business. There
is plenty of money riding on it. The real world is like that, trivia
can get way more money than they deserve sometimes.
Oh, it is definitely a no-no.
How can distortion products that are present in every audio amp be a
nono??
Regarding scientifically *demonstrable* human ability to detect
distortion, it is a reality and has been for some time. Sure, some
folks *claim* ability to hear minute levels of distortion, but they
haven't been able to demonstrate it.
Maybe they can detect it, but who else cares since the information to
really know is exceedingly expensive?
1. hobbyists and consumers
2. everyone in the business of supplying those customers
3. people doing business with the above market sector
It is probably cheaper for those
who make these claims to simply buy the stuff they believe is best than
to prove the matter scientifically. But this is *sci* electronics
design. Without science, it is irrelevent here.
Most of us are commercial designers. To those of us in the consumer
sector, it matters alright. Whether its science or nonsense it still
matters. Those of us who designed feedforward amps enabled our
employers to make a song and dance about the fact, regardless of
whether it held any advantage outside of sales. Do you remember /know
about when hifi amps broke the 0.1% barrier in the 50s? Big hoo-ha over
that, financial futures made and broken on that one. The same game can
be repeated.
IMO, the people who make these claims should stop making claims they
can't prove. They should simply say it is their belief. Then their
subjective wants, and real purchases are based on those beliefs, can be
made and no rational justification is needed.
Its an option.
I have no way to prove to you that modulation makes tinny amps sound
better, but I still believe it does, and will still act on that belief
with good reason, even if its not been proven to you.
There is a better way to phrase the distortion control techniques in
audio amps. The intent is certainly to *cancel* distortion, and in fact
this is what is done. It is only that it cannot be "done" in the
absolute (zeroed) -- it cannot *totally* cancel it. To say it is
lowered is indeed to say it is cancelled or controlled *to a measure*.
both have been done, cancellation is not the sole technique
This is huge, I'd be surprised if I ever get the time for another
round. Happy designing.
NT
