John Curl's Blowtorch preamplifier part II

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#31,562
I have no reason to believe the 862 published specs over anothers' Unless one has measured them both.

RF devices are often very linear as they cannot produce IM products that cause RFI issues and are mostly run class A. But they cant use pcb layouts that are not done with RF expertise.

As long as I have to build something rather than a machine, thru hole parts are my first choice. And, this is a DIY forum. If it wasnt, we would be talking about/assuming the smd all the time.

-RNMarsh
 
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#31,565
Enjoy, Waly. I happen to have a jar full of 2SK152's, along with several thousand even better (for most applications) parts, so I tend to be lazy. However, I do use adaptors when I need to. The ACTUAL performance between the 2SK152 (leaded) and the 862 (surface mount) is trivial.
 
#31,568
john curl said:
Enjoy, Waly. I happen to have a jar full of 2SK152's, along with several thousand even better (for most applications) parts, so I tend to be lazy. However, I do use adaptors when I need to. The ACTUAL performance between the 2SK152 (leaded) and the 862 (surface mount) is trivial.
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The Motorola part you asked me about was the MPQ6600,A. A quad bjt package of complimentary pairs. I used it for my first line stage of my 'diamond amplifier' configuration. Later on, published in TAA. Very low distortion. Mototrola doesnt make it any more, but I see On Semi and others still have it.... good to VHF (only) 🙂 -RNMarsh
 
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#31,569
Much better to demonstrate that people who think they can distinguish really can do it, then the scientist will be sufficiently intrigued to ask 'How?' and 'Why can't I do it?'.
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Jakob2 said:
If the contention is true, then even a good scientist will not work as a good detector if he is biased against the audibility of a certain effect.
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One feature of a properly conducted Blind Listening ABC Test as I've described, where each subject has 'unlimited' time to judge the 3 presentations is that EVERYONE hears differences ... whether scientist, true golden pinnae or pseudo Golden Pinnae.

But true golden pinnae will say something like "I think A & C are similar with C maybe a little brighter. I don't like B cos but can't explain why." The self declared pseudo Golden Pinnae will hear Chalk & Cheese differences even if all three presentations are the same item. You begin to distinguish between the Blind & the Deaf when you repeat the test.

I've never said the expected result of a Blind Listening Test is a NULL result. The truth is that SOME people under SOME conditions can hear amazingly small differences. Other people will claim they can hear tiny differences but are unable to demonstrate this unless each presentation is clearly labelled "evil 4558" or "$zillion" etc. 😱

Who are you going to ask about whether evil 4558 sounds better than Blowtorch?

As mentioned before, a good start could be to set up a listening test without revealing the effect under test.
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This is fundamental to my ABC Blind Tests. Our hypothetical 😡 test is already flawed cos Blowtorch has to be a contender. But we may or may not put in the evil 4558. 😀

JC, in your zillion years as a High End designer, surely you know at least one person with true golden pinnae that you would trust to pick up the superlative qualities of Blowtorch vs evil 4558? Someone still alive ? 🙂
 
#31,571
kgrlee said:
a properly conducted Blind Listening ABC Test as I've described, where each subject has 'unlimited' time
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Why ?
Can't we assert that, or a difference is obvious, or it means we do not have to take care of ?
When two samples are so close that it needs a lot of concentration and time to ear any difference, only "maniac" audiophiles would try to distinguish from them a Grail from a Garbage, reasonnable people will give them the same note and only look at the price between them 🙂
Of course, the sources had to be carefully chosen to reveal different aspects, (Dynamic, details, ambiance, including non musical samples where no taste is involved, like life's ambiances and noises)
 
#31,573
Now I would like to talk about the 'future' of amps and preamps. The latest issue (Jan'13) of Stereophile came this week and some new products were reviewed, that show the future we are working on in amp design. We are working with combinations of Class D and Class A to make relatively lightweight, powerful amplifiers. This is not an 'amateur' project, but it is the 'future' and what I have been working on with another couple of designers for the last few years. We showed the amp at Rocky Mountain audio a few years ago, and it has undergone constant revision since.
 
#31,578
john curl said:
Now I would like to talk about the 'future' of amps and preamps. .....We are working with combinations of Class D and Class A to make relatively lightweight, powerful amplifiers.
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Looks like nothing is gonna save us from the future 🙁. Wouldn't it be better to discuss this in a separate design thread, this one has been intended for highest quality linear design. I understand you have to make a living somehow, but this is too much regarding this thread.
 
#31,579
The desire to have "class a without the heath" is as old
as amplifier technology, I believe.
"new class a", "class aa", "optical class a", "dynamic bias"
"sustained plateau bias" ... etc. none of them did really live up
to their claims. We will see if this class d + a combination
does the trick. I´m sceptical. (there are no shortcuts to perfection).
 
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