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Naim = bright?

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Paul R said:
One or the other is already on. The drive to the output stage is bandwidth limited, so I'm not sure where you are going.

Much more interesting than 'bright' for an amp with a flat response though.

Paul
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If the output devices had a small enough turn on time or the quiescent current was high enough then I could see your argument. Take it from when one device is conducting, then take the waveform through to the other device conducting, now given that it takes a finite time to switch the device on and the other device is switching off, why should there always be one device on?
 
sergeauckland said:
The purpose of HiFi equipment is to reproduce what is on the CD with the minimum of change and to render a larger version of what went in. No more and no less.
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Well that's your definition. I would say that the purpose of a Hi-Fi system was to communicate the technical and artist aspects of the original performance as accurately as possible.

The problem with your definition is that it's got its head stuck over a bench, it's very you! ;0) But it has some issues. For example, it assumes that all the information you need is actually on the CD and can be reproduced. When it clearly isn't and can't be. A Hi-Fi system and the room it is in have to add colouration to the sound produced if are to stand any chance of producing something lifelike.

The problem, it seems to me is that subjectivists are only concerned with what their own experiences tell them...
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Quite, and I agree that our senses can be easily fooled. But if you take the stance that our senses can never be trusted you are just as wrong, only in the other extreme. And you also loose any credibility that blind tests might have as it would mean that their results cannot be trusted either!
 
russel said:
If the output devices had a small enough turn on time or the quiescent current was high enough then I could see your argument. Take it from when one device is conducting, then take the waveform through to the other device conducting, now given that it takes a finite time to switch the device on and the other device is switching off, why should there always be one device on?
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Because that's the definition of Class AB. Class A has both output transistors on for the whole cycle, Class B has one transistor on for the positive half cycle and off for the negative whilst the other is the opposite, whilst Class C has each transistor on for less than one half-cycle. Clearly Class C is of no use for audio, but has applications in RF tuned amplifiers.

In the case of class AB, each transistor is on for more than one half cycle but less than the whole cycle. Consequently, at around the point of zero crossing, both transistors are on simultaneousy and both are conducting. The problem comes with non complementary-symmetry outputs that one transistor outputs from the collector and the other from the emitter and so have different transconductance and hence output impedances on the two half-cycles, and that can give rise to non-linearities which no amount of feedback can remove, although can reduce it to the point where it's inaudible. Later fully complementary output stages had both transistors outputting from their emitters, so although there was a small difference between pnp and npn performance, it was very small compared with both being npn.

S.
 
Mr Pig said:
Well that's your definition. I would say that the purpose of a Hi-Fi system was to communicate the technical and artist aspects of the original performance as accurately as possible.

The problem with your definition is that it's got its head stuck over a bench, it's very you! ;0) But it has some issues. For example, it assumes that all the information you need is actually on the CD and can be reproduced. When it clearly isn't and can't be. A Hi-Fi system and the room it is in have to add colouration to the sound produced if are to stand any chance of producing something lifelike.



Quite, and I agree that our senses can be easily fooled. But if you take the stance that our senses can never be trusted you are just as wrong, only in the other extreme. And you also loose any credibility that blind tests might have as it would mean that their results cannot be trusted either!
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Hot air.
 
Mr Pig said:
Quite, and I agree that our senses can be easily fooled. But if you take the stance that our senses can never be trusted you are just as wrong, only in the other extreme. And you also loose any credibility that blind tests might have as it would mean that their results cannot be trusted either!
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Which is why I said that blind tests have to be statistically valid. One person taking a blind test once could just be guessing. One person taking the test 20 times and getting 90% right, shows that there's a strong probablity of that one person being capable of hearing a difference. Now take 1000 people selected according to some criteria taking 20 tests each, and one can get a fair idea of what is possible in the selected population.

I am not a statistician, so I cannot say at what point and with what results one can be reasonably sure of a result, however these things are known and practiced.

Both the Moir Associates and Martin Collums tests on amplifiers showed that the listening panels, selected amongst audio journalists and professionals, were unable to hear any difference between the various amplifiers. My own tests done in the mid '80s showed the same for me, but then one could say I'm deaf so that's no surprise.

S.
 
sergeauckland said:
In the case of class AB, each transistor is on for more than one half cycle but less than the whole cycle. Consequently, at around the point of zero crossing, both transistors are on simultaneousy and both are conducting. The problem comes with non complementary-symmetry outputs that one transistor outputs from the collector and the other from the emitter and so have different transconductance and hence output impedances on the two half-cycles, and that can give rise to non-linearities which no amount of feedback can remove, although can reduce it to the point where it's inaudible. Later fully complementary output stages had both transistors outputting from their emitters, so although there was a small difference between pnp and npn performance, it was very small compared with both being npn.

S.
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Thanks, nice textbook description. However we are dealing things like emitter resistors as well and temperature effects which will cause deviations from the ideal scenario you have described above.
 
russel said:
Thanks, nice textbook description. However we are dealing things like emitter resistors as well and temperature effects which will cause deviations from the ideal scenario you have described above.
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Firstly, emitter resistors are not necessary, some amplifiers don't have them. The main value of emitter resistors is that it gives a simple way of providing over-current protection! Secondly, and I can only go by my experiences here, the text-book definition has held every time. That's exactly how a practical Class AB amplifier works.

S.
 
sergeauckland said:
If you have a different definition of purpose, for example, to give maximum pleasure, that's your definition, and you have to judge your equipment choices against that.

S.
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And that of course is how the majority judge their equipment, not whether it has perfect technical performance but whether it gives musical pleasure, who listens to numbers? Most of us listen to music don't we?

There was a clever advert years ago, the 3 wise men were listening to the Herald angels singing, one of them said, I think I hear some midrange Honk.
Errol.
 
Blzebub said:
Do you think the people who design and fix vacuum cleaners don't know how they work? This hi-fi mysticism is instilled by the manufacturers, some of whom would have you believe that designing hi-fi is an "art".

The old story about things measuring the same but sounding different is so obviously untrue as to be barely worth discussing. If two things actually do sound different, you can bet your bottom dollar that the difference is measurable.
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Think you're slightly missing the point, James. What I've been saying is I don't care how something measures, I'm only interested in how something sounds to me and you can't tell me how that is going to be by measurements. For that I'm afraid the only way to know is by listening. That's the point.
 
sergeauckland said:
But I do. The purpose of HiFi equipment is to reproduce what is on the CD with the minimum of change and to render a larger version of what went in. No more and no less.

If you have a different definition of purpose, for example, to give maximum pleasure, that's your definition

S.
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Yes, that's it.

Now please stop trying to force your definition onto the majority.
 
sergeauckland said:
Which is why I said that blind tests have to be statistically valid.
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Yes, but you are assuming no possibility of listener error. You are happy to assume those hearing differences are wrong but assume those hearing no difference are correct without entertaining the possibility of the test methodology effecting listener perception. It's valid because you want it to be.

Blind listening tests are not proof of anything. Unlike other superficially similar scientific tests they rely on subjective opinion. You can talk about facts, data and statistics but as these are all coming from a bunch of humans they can still be wrong.

But you can't concede that possibility can you?
 
sergeauckland said:
You mean as you do, the mantra that the only thing that matters is what it sounds like? ;)

S.
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Except I don't go around crapping on thread after thread where by the initial post it's clear my "mantra" isn't invited.

I've never needed blind listening tests or level matching to help me realise many things sound the same to me that other people think sound different, I have plenty of examples that I won't repeat yet again. It means when I do hear something that I think is different to something else, I'm secure enough to believe it.
 
"Personal experience is the weakest form of evidence."

I read this in an article talking about various fitness and weight loss claims. It struck a chord with me regarding this threads debate.
 
chainrule said:
"Personal experience is the weakest form of evidence."

I read this in an article talking about various fitness and weight loss claims. It struck a chord with me regarding this threads debate.
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Important for those looking for evidence.
 
Brian said:
Except I don't go around crapping on thread after thread where by the initial post it's clear my "mantra" isn't invited.
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We might as well close the forum, 'cause there's nothing left to discuss if Serge is right.
 
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