John Curl's Blowtorch preamplifier part II - Page 2795 - diyAudio
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Old 2nd October 2012, 07:53 PM   #27941
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SY, I design for low distortion, BUT not with heroic amounts of negative feedback to get me there. I am suspicious of global negative feedback, especially when it tends to lower the open loop response. I ALWAYS look out for odd order harmonics, but below -110 dB, then perhaps they are not so important.
There is more to audio sound quality that steady state distortion. That is my opinion and experience.
For balance, the Halcro preamp got a bad review in 'Hi Fi News' years ago. Something about the digital power supply effecting the rest of the equipment in a bad way.
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Old 2nd October 2012, 08:10 PM   #27942
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And for all your suspicion, here's one that has superb measurements and won the "listening contest."

After getting data contrary to a hypothesis, some might conclude that the hypothesis is flawed.
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Old 2nd October 2012, 10:33 PM   #27943
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Old 2nd October 2012, 11:05 PM   #27944
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Quote:
Originally Posted by john curl View Post
'High end' for me is the effort to eliminate higher order distortions that can give listening fatigue, as well as to attempt to effect a 'you are there' at least for a moment experience with a lot of musical sources. For this, often 'inner details' in the music become apparent, and this can help to make it more realistic sounding. You know, when the applause actually sounds like hands clapping, rather than some sort of 'mush', or you get 'goosebumps' from the performance.
Exactly. Unfortunately, this is in the "devil's in the details" area, in my experience. When I get to this point the slightest variation from optimum causes the subjective quality to plummet, it's a very fine balancing act. One of the reasons is that when the SQ is spot on then you can wind up the volume as far as you like with no problems, this is in the territory of being able to go outside the house and the music inside still sounds completely realistic. But, at these volumes the slightest audible deficiency sounds horrendous, it is instantly unlistenable to ...

Very much, razor's edge territory ...

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Old 2nd October 2012, 11:08 PM   #27945
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A hypoth that a super low THD+N in a power amp listening contest would NOt mean that only THD+N was the reason for a win. Or, sole reason. PSRR, PS noise, regulation of the PS under those load conditions, CMRR, peak current into various load Z, output Z et al are needed to get an over-all evaluation of the total parameters that lead to the decision. AND, how the total harmonic structure combined in That system being used in the listening test. -RNM

Last edited by RNMarsh; 2nd October 2012 at 11:20 PM.
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Old 2nd October 2012, 11:20 PM   #27946
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Perhaps all that ties into the (according to John) super high levels of "global" feedback. The THD performance is just part of the picture, the result of excellent engineering, not a specific desideratum in and of itself. It performs well because the designer knew what he was doing and didn't reflexively dismiss using good engineering practice because of being stuck in 1968 thinking.

The "listening contest" performance has very little- or perhaps nothing- to do with actual listening, but clearly the designer knew how to make something that looks and feels impressive as well.
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Old 3rd October 2012, 12:18 AM   #27947
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Also known as, everything matters. Such a glib thing to say, rolls off the tongue so easily ...

And also practically universally ignored ...

Frank
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Old 3rd October 2012, 12:55 AM   #27948
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SY, I designed a line driver for Sound Technology in the 1980's that had about -100dB of distortion at 100KHz. Much less than that below 100KHz. I just do not use that design approach for audio listening, just instrumentation.
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Old 3rd October 2012, 05:44 AM   #27949
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Everything matters, fas42! That's how it gets made right. '-)
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Old 3rd October 2012, 06:50 AM   #27950
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Quote:
I just do not use that design approach for audio listening, just instrumentation.
I think I already know the answer, but just to be sure...
Because for listening, that approach just doesn't end up sounding right?
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