Sorry about that ... 🙂
The test 'fail' because they don't connect remaining 'imperfections', as there always will be, with what is subjectively important. So, any amplifier can be tested for maximum output, which in one sense is meaningless, because it can be driven into severe clipping, and the average output then is way above the 'quoted' figure. I see the limits being 1% distortion, or even 10% distortion if the designer is game, 😀, - but is that distortion acoustically benign, like typical reel to reel tape overload? Why, the studio engineers actually still deliberately introduce that type of distortion as an "effect", and many of the most famous and desired recordings are riddled with those levels of distortion - strangely, that type of 'abberation' doesn't send the listeners screaming out of the room ... 😉.
So, distortion is not just simple distortion - some will lull you to sleep, other types will induce you into wanting to put a sharp object through the driver, 😀 ...
In my book, just saying the amplifier has a certain maximum output, and the distortion levels will be so or so, in certain instances, tell me close to zero about how it will sound in real life - the subjectively importantly details about in what way it distorts are missing: the power opamps I've been listening to for months have pretty terrible, 'book', distortion levels - as 'junky' as any half hearted tube amp you see around -- yet they're doing a very nice job of reproducing satisfying sound. They are distorting, they must be, the datasheet spec's tell me that they will - but, after tweaking, that aspect is not degrading the sound in the key ways that typical hifi setups do ...
The amplifier working 'hard', at high powers, with conventional power supplies will inject a high level of noise into the mains supply - very nasty current spikes from the rectifiers firing will mean the noise level of the mains being fed to, say, the CD player will deteriorate, and vary, precisely in step with how loud the system is at any particular moment. So, the consumer relies on the cheap power supply in the source electronics being absolutely brilliant in isolating the sensitive circuitry within from this modulated noise ...
Environmental factors going the other way then also effect the amp, the quality of the power going into it change the equation. Also, being sensitive to RF interference - say, do the speaker cables, often being excellent antennae, pick up high frequency rubbish and disturb correct behaviour?
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I'm curious why this myth of once again those stupid, stupid engineers not knowing, not applying systems related testing - like virtually all of the CE EMI susceptibility and emissions tests, military, especially navel electronics system interface requirements and testing regimes, medical systems testing...
.. sure a lot of garage level “high end” audio amp builders may never have heard of such – but to say the principles, methods are unknown to EE equipment designers, pro audio designers is a stretch
.. sure a lot of garage level “high end” audio amp builders may never have heard of such – but to say the principles, methods are unknown to EE equipment designers, pro audio designers is a stretch
Not unknown - but poorly implemented, in the real world ...
I can't go out and simply purchase what I would call a correctly working audio system - without doing a huge amount of research, and after sales "fixing" to resolve the issues. In other areas of similar activity the engineers would be laughed out of the building for doing things in such a haphazard way ...
Edit: an example - at the audio show there was one correct system, using Dynaudio speakers. Ahhh, says the perceptive listener, Dynaudio know what they're doing, a system using their product will end up with good sound. So, go the main Dynaudio demo area, and listen to units slightly less ambitious in the product line ... dreadful, dreadful sound - would put one off hifi for life! This is so typical of the industry - it's a mess ... !!
I can't go out and simply purchase what I would call a correctly working audio system - without doing a huge amount of research, and after sales "fixing" to resolve the issues. In other areas of similar activity the engineers would be laughed out of the building for doing things in such a haphazard way ...
Edit: an example - at the audio show there was one correct system, using Dynaudio speakers. Ahhh, says the perceptive listener, Dynaudio know what they're doing, a system using their product will end up with good sound. So, go the main Dynaudio demo area, and listen to units slightly less ambitious in the product line ... dreadful, dreadful sound - would put one off hifi for life! This is so typical of the industry - it's a mess ... !!
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Yes, hopefully at present we (or at least Fas42 and myself) are trying to clear something apparently important - because over years the apparent 'difference' between real-world equipment (amplifiers in this case) and 'scientists/engineers in boxes' has resulted in the very thing you call circular semantics .... because the basics have never been fully addressed/understood/accepted. If unimportant, why does it keep recurring?
If you find it uninspiring, my apology - it happens. If it is unimportant/boring for others, I apologise. I am hoping that we will get a better understanding of certain basics always glossed over, with the inevitable result mentioned above.
And I do thank the author for allowing latitude in the original thread title. I hope he agrees that a wider view is sometimes necessary.
By the way both Fas42 and myself are EEs - no petty point-scoring on the agenda.
Some amplifiers (e.g. SET with no or little feedback, some unusual SS amps with no or little feedback) have a forward gain which varies with supply rail voltage. If such an amp is fed from an unstabilised power supply then the amplitude of the output signal may depend to a small extent on the amplitude slightly earlier. Using adeqate feedback will eliminate this problem. Using a stabilised PSU will eliminate the problem for valves, but just leave junction thermal effects for SS.TimBoz said:
Curiously, the sort of amps which might suffer from this problem are sometimes favoured by those who think they have gone 'beyond' conventional engineering.
I do not think that in hifi context is something called tube sound, but there are definitely good and bad amplifiers. I consider an amplifier to be poor if it colors the sound ... I only want to hear the sound as it is.
However, when it comes to music production, it is an entirely different matter. For me there is no doubt that guitar amps with tube sounds best. This is especially true when driven into distortion (crunch) ... there are the tubes clearly the best.
We should keep far from overdriving and go for pure sound ... it's something different and here divides the tubes not so significantly from the transistors. But there is still benefits from a good tube amp. I think the one I have is extremely dynamic and is impossible to provoke to make bad habits.
I have Pioneer and Marantz amps an they do sound allright...but it sounds a bit better with the tube amp...more life.
However, when it comes to music production, it is an entirely different matter. For me there is no doubt that guitar amps with tube sounds best. This is especially true when driven into distortion (crunch) ... there are the tubes clearly the best.
We should keep far from overdriving and go for pure sound ... it's something different and here divides the tubes not so significantly from the transistors. But there is still benefits from a good tube amp. I think the one I have is extremely dynamic and is impossible to provoke to make bad habits.
I have Pioneer and Marantz amps an they do sound allright...but it sounds a bit better with the tube amp...more life.
Output impedance
Audio amplifiers are usually loaded by loudspeakers and in the history nearly all loudspeakers have been electrodynamic loudspeakers, while there exists also minority of electrostatic loudspeakers and some other even more exotic loudspeakers. Electrodynamic loudspeakers transform electric current to force and force to acceleration of the diagraphm which causes sound pressure. Due to the principle of an electrodynamic speaker, most loudspeaker drivers ought to be driven by an electric current signal. In an ideal current or transconductance amplifier the output impedance approaches infinity, while practically all commercial audio amplifiers are voltage amplifiers, and their output impedances have been intentionally developed to approach zero. Due to the nature of vacuum tubes and audio transformers, the output impedance of an average tube amplifier is usually considerably higher than of the modern audio amplifiers produced completely without vacuum tubes or audio transformers. Thus, most tube amplifiers with their higher output impedance are closer to the idea of a transconductance amplifier than the solid state voltage amplifiers. The current signal drives the electrodynamic speaker more accurately, causing less distortion than a voltage signal.
Tube sound - Wikipedia, the free encyclopedia
Audio amplifiers are usually loaded by loudspeakers and in the history nearly all loudspeakers have been electrodynamic loudspeakers, while there exists also minority of electrostatic loudspeakers and some other even more exotic loudspeakers. Electrodynamic loudspeakers transform electric current to force and force to acceleration of the diagraphm which causes sound pressure. Due to the principle of an electrodynamic speaker, most loudspeaker drivers ought to be driven by an electric current signal. In an ideal current or transconductance amplifier the output impedance approaches infinity, while practically all commercial audio amplifiers are voltage amplifiers, and their output impedances have been intentionally developed to approach zero. Due to the nature of vacuum tubes and audio transformers, the output impedance of an average tube amplifier is usually considerably higher than of the modern audio amplifiers produced completely without vacuum tubes or audio transformers. Thus, most tube amplifiers with their higher output impedance are closer to the idea of a transconductance amplifier than the solid state voltage amplifiers. The current signal drives the electrodynamic speaker more accurately, causing less distortion than a voltage signal.
Tube sound - Wikipedia, the free encyclopedia
This is an interesting point. But what puzzles me is that surely manufacturers these days will be designing loudspeakers for the conventional low output impedance of SS amplifiers, and hence for voltage drive rather than current drive? Wouldn't it be odd if a loudspeaker designed to be voltage driven actually performed better when current driven?
Another, related, point is that the actual impedance of a loudspeaker is extremely frequency-dependent. If it is producing roughly constant sound-pressure level across the frequency spectrum when the driving signal voltage is constant as a function of frequency (and this is presumably what the manufacturer designs for), then it will produce a hugely non-constant sound-pressure level across the frequency spectrum if the current is instead constant as a function of frequency.
So, I would have thought that whether voltage drive or current drive is better would depend amost entirely on whether the loudspeaker was designed for voltage drive or current drive.
Chris
sorry but the overwhelming standard is that loudspeakers expect to be driven by near Vsources - the drivers are carefully engineered to give their expected flattish response with V drive - in multiway the XO is designed with the assumption of Vsource drive
you can avoid some nonlinearities of dynamic speaker drivers with current drive - but then you need substantial EQ to bring the response back to flat
The current drive bandwagon seems to be gaining momentum. It is, of course, based on an oversimplification - I was going to say a fallacy but that seemed rude.
It is true that force comes from current, but that completely ignores the induced voltage caused by velocity. The result is that motion actually more closely follows voltage than current. To make a speaker where motion corresponds to current you need to add lots of mechanical damping. As a result such a speaker can't be used with a conventional voltage output amp.
To give an analogy, it is as though someone claimed that as transformers depend on (rate of change of) primary current they should always be current driven too.
It is true that force comes from current, but that completely ignores the induced voltage caused by velocity. The result is that motion actually more closely follows voltage than current. To make a speaker where motion corresponds to current you need to add lots of mechanical damping. As a result such a speaker can't be used with a conventional voltage output amp.
To give an analogy, it is as though someone claimed that as transformers depend on (rate of change of) primary current they should always be current driven too.
Well, that's rather much what I thought. "Power driven" is anther school of thought, which is a sort of geometric mean between voltage driven and current driven. I would have thought that, as you say, it is really voltage that controls the movement of the speaker cone.
And another thing, which strikes me, is that the (rather absurd, in my opinion) arguments about the effect of different cables, and the like, are of the uttermost insignificance compared with the effects of different speakers, and the output impedance of the amplifier.
Chris
seems like a massive discourse on subjectivity - to be honest, this has always been one , if not the most, biggest problems in audio since day one. What I think sounds good you may think sounds like crap - there is no scientific way to settle the argument. From the perspective of a manufacturer all that matters is the majority opinion - like the old saying you cant please all the people....
if the majority of users fell your gear or your sound is "good" thats about the best you can do. The only way to refine the issue would be to first get unanimous agreement on what is "good" sound. But I don't see that happening anytime soon. So until then, each of us will have our own preferences and thats the way it is.
Gary Ferguson
if the majority of users fell your gear or your sound is "good" thats about the best you can do. The only way to refine the issue would be to first get unanimous agreement on what is "good" sound. But I don't see that happening anytime soon. So until then, each of us will have our own preferences and thats the way it is.
Gary Ferguson
The aim of hi-fi is not 'good sound' but 'authentic sound' - it sounds like the original sound. This can be determined scientifically by seeing whether people can distinguish reproduction from live instruments. Tests done this way indicated roughly what performance was needed from the electronics. Make the electronics a bit better than this and it is found that people can't reliably distinguish (by ears alone) between different electronics.gfergy said:
Note that individual preferences are not the issue - people may hate the sound of hi-fi and choose to buy something else. What they should not do is claim that their preferred distortion is somehow more authentic than the much smaller distortion which true hi-fi requires.
This is again something of a ludicrous proposition in the field of HIFI and recorded music. Nearly all music is highly modified (compressed) in the recording process so will never sound like the original live performance. Most music isn't even live these days and much is purely artificial.
More chasing of that dream.
Shoog
but many arguments that contain this theme have logical problems - we all must share a great deal in our perception of natural sound, our individual neural nets already compensate for minor physiological variations - how else do musicians learn, then play together - why do audiences enjoy the results
then there is often the elide into recorded music home reproduction - I always smile at the "realism" comments
modern music recording is itself an interpretive art form with many "unnatural" manipulations from the performance venue vs isolated booths in a studio, to micing choices, thru mixing/mastering - and overwhelmingly the choices are made for commercial success - which entails exploiting audio illusions, cultural conventions, exaggerations, omissions, "hyper realism"
For Rock and Pop maybe. I've found many good (dynamic range) recordings in Jazz and Classical music.
Since this topic has diverged for the moment into a discussion of speakers I will pose a question that has been nagging me for a while.
My main speakers are Klipsch Heresy (HBL) from 1976. The design was introduced in 1950 as far as I can find. I'm sure there were changes before the Heresy II in 1985, but I expect they were probably minor. Same for the HIII in 2005.
I know the crossover frequencies changed and efficency increased with each variant.
What I'm wondering about is the compatibility (optimal) for the different versions with respect to being driven by a tube amp vs SS. My suspicion is that part of the reason for change was to product a speaker more in tune with SS amps.
If this is so, then the first generation speakers are the best choice when a tube amp is to be used.
My main speakers are Klipsch Heresy (HBL) from 1976. The design was introduced in 1950 as far as I can find. I'm sure there were changes before the Heresy II in 1985, but I expect they were probably minor. Same for the HIII in 2005.
I know the crossover frequencies changed and efficency increased with each variant.
What I'm wondering about is the compatibility (optimal) for the different versions with respect to being driven by a tube amp vs SS. My suspicion is that part of the reason for change was to product a speaker more in tune with SS amps.
If this is so, then the first generation speakers are the best choice when a tube amp is to be used.
Most of the people suggesting the use of transconductance amps only do so with regard to driving single fullrange speakers. In this application they achieve everything that is claimed of them. However they advocate the use of balancing networks to smooth the response.
Shoog
Shoog
People often bring up the red herring of much modern recorded music being quite artificial. All that means is that you should not use it for even informal evaluation of a hi-fi system. By all means use it to check your preferred 'sound'.
The reproduction I was talking about is a comparison between:
instrument or ensemble
vs.
the same, but heard via a microphone, amplifier, loudspeaker system.
This test shows what level of performance is required to satisfy most people. By 'satisfy' I don't mean 'nice sound' but 'indistinguishable from live music'.
If equipment is then safely superior to what the test indicates (to give a margin for error) then something which should be expected is that different examples of such equipment (i.e. different circuits, different measurements but still good enough) should be indistinguishable by ear alone. This is what seems to be found, with very few exceptions. Some of those exceptions seem to be due to listeners noticing correlated but irrelevant factors such as switching clicks. The whole picture is thus self-consistent.
Such equipment can then be used to reproduce both realistic music and highly processed music with a reasonable expectation that it will indeed simply reproduce it. Some people prefer something else, and that is their choice.
Remaining claims about difference probably fall into just a few camps:
1. a few listeners may really be much better at hearing; I suspect that this group does not include nearly as many DIYers or audio journalists as they fondly imagine.
2. lucky correlations, such as clicks.
3. the EM environment, which is difficult to control and test - few audio tests are done in screened rooms and in any case an amplifier must work in the real world of RF pollution.
The reproduction I was talking about is a comparison between:
instrument or ensemble
vs.
the same, but heard via a microphone, amplifier, loudspeaker system.
This test shows what level of performance is required to satisfy most people. By 'satisfy' I don't mean 'nice sound' but 'indistinguishable from live music'.
If equipment is then safely superior to what the test indicates (to give a margin for error) then something which should be expected is that different examples of such equipment (i.e. different circuits, different measurements but still good enough) should be indistinguishable by ear alone. This is what seems to be found, with very few exceptions. Some of those exceptions seem to be due to listeners noticing correlated but irrelevant factors such as switching clicks. The whole picture is thus self-consistent.
Such equipment can then be used to reproduce both realistic music and highly processed music with a reasonable expectation that it will indeed simply reproduce it. Some people prefer something else, and that is their choice.
Remaining claims about difference probably fall into just a few camps:
1. a few listeners may really be much better at hearing; I suspect that this group does not include nearly as many DIYers or audio journalists as they fondly imagine.
2. lucky correlations, such as clicks.
3. the EM environment, which is difficult to control and test - few audio tests are done in screened rooms and in any case an amplifier must work in the real world of RF pollution.
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