I just called up Peter Schüller and his secretary said he calls me back. I hope he has a PDF or something i can publish here. I am a liitle lazy to scan the magazine and have to claryfy anyway if i am alowed to publish it on the web.
I would like to see the article too. In general MLS and some other psuedo-random sequences are not meant to be used truncated, it violates the mathematical basis of their usefulness. That is the autocorrelation of an MLS sequence is an impulse, the autocorrelation of the first 100ms of a 1 sec MLS is (probably) garbage.
Well, when we can, let us see if this makes for a significant difference.
The late Richard Heyser once told me of a similar problem in measuring with a high feedback amp, perhaps 40 years ago. He said that the power amp had to settle down between level settings changes to measure distortion and this was unnatural. He didn't think much of feedback either, and Richard Heyser was the first person to tell me about real measurements of the voltage coefficient of resistance in certain resistors that he had measured (also 40+ years ago). We seem to 'discover' the same things, over and over, until they finally get into a textbook, I guess. ;-)
The late Richard Heyser once told me of a similar problem in measuring with a high feedback amp, perhaps 40 years ago. He said that the power amp had to settle down between level settings changes to measure distortion and this was unnatural. He didn't think much of feedback either, and Richard Heyser was the first person to tell me about real measurements of the voltage coefficient of resistance in certain resistors that he had measured (also 40+ years ago). We seem to 'discover' the same things, over and over, until they finally get into a textbook, I guess. ;-)
High feedback amps, particularly cheap commercial ones, are probably biased weak A/B and therefore are prone to large thermal deltas when a signal is suddenly applied. This can be designed around and has nothing to do with feedback.
I have seen a Heyser article where he mentinioned that the phase of the distortion products should be mesured too. I know at least one amp designed by Michael Yee and Drian Daily over a period of 20 years that is based on that asumption.
( i think he thought about harmonic distortion like second and third harm.)
Well, i am in no way an expert on feedback theory so i just try to communicate was others tell me.
( i think he thought about harmonic distortion like second and third harm.)
Well, i am in no way an expert on feedback theory so i just try to communicate was others tell me.
Joachim, you are just beginning. Trust me on this. However, it is best to know, rather than speculate. Not because of me, but because others, who, without your understanding and appreciation for audio differences, will seek to undermine what you DO know well, by bringing up here doubts about what you might have overheard, and not PROVEN to their satisfaction.
Hello Joachim
I have a couple of questions when you say high feedback amplifiers do you also mean that they were low distortion also.
As you have mentioned the high distortion amps (low feedback) Ayre, Pass, Brinkmann et could you tell us what the name of the high feedback (I assume low distortion) amp is the one that measured badly on this speaker amp interface test.
Regards
Arthur
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They measure at lot of multichannel amps, mostly from Japan that measure great on static didtortion tests like Denon, Yamaha, Rotel ... you name it that did not so well on this test. There was a Harmon Kardon model that behaved better. I have to look up the exact model. Sorry, i am not so good to remember those silly name choices like KPSU9675SE.
John, ok, no more speculations, more prove in the future. I need some time to persuade my brain about that message. You know i am more the intuitive, practical guy.
John, ok, no more speculations, more prove in the future. I need some time to persuade my brain about that message. You know i am more the intuitive, practical guy.
Well, we wait until we get some input from this new test. Or maybe we go on to a different topic while we wait.
As far as detailed measurements are concerned, often we cannot tell what an amplifier or a preamplifier sounds like, just by measurements. Sometimes, our excessive zeal to measure some component, such as a resistor, is because we hear the differences first, but don't have a definitive reason why there is a difference between quality resistors in the first place. Now, please, let us not go back to the tired refrain of what we can hear. I have to make these decisions, myself, as a designer, and denying differences is unproductive.
In 'Stereophile' a LTE from a reader who does not know me, personally, thought that I could not believe in such nonsense as 'Trusting my ears'. I had to set the situation right.
We might have become temporarily stuck here so I while try to kick the discussion in "some" direction if that's ok.
As I guess none have yet seen the paper one thing one would have to assess as well is how the high FB/low out Z amplifiers behave with a loudspeaker dummy load, can we still see the artefacts in the first 100 ms or is it something that occurs in conjunction with a real speaker load only and why.
As far as I know the loudspeaker itself actually don't like low Z out amplifier and the system distortion goes up, so a second thing to ponder over is.. is the artefacts bound MORE to the amplifier itself OR the loudspeaker, that's something one should look into closer.
John what's your take on it, hopefully Joachim will chime in too as he knows at least the dynamic transducer.
Cheers Michael
As I guess none have yet seen the paper one thing one would have to assess as well is how the high FB/low out Z amplifiers behave with a loudspeaker dummy load, can we still see the artefacts in the first 100 ms or is it something that occurs in conjunction with a real speaker load only and why.
As far as I know the loudspeaker itself actually don't like low Z out amplifier and the system distortion goes up, so a second thing to ponder over is.. is the artefacts bound MORE to the amplifier itself OR the loudspeaker, that's something one should look into closer.
John what's your take on it, hopefully Joachim will chime in too as he knows at least the dynamic transducer.
Cheers Michael
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