John Curl's Blowtorch preamplifier part II - Page 3156 - diyAudio
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Old 18th December 2012, 05:40 AM   #31551
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Quote:
Originally Posted by RNMarsh View Post
I'm trying to get the oscillator in an HP339A as low in H2 and others as is humanly possible.
Are-you sure the oscillator itself achieve such a low distortion ? Or the way they cancel the original signal from the measured signal ?
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Old 18th December 2012, 09:03 AM   #31552
Jakob2 is offline Jakob2  Germany
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Quote:
Originally Posted by DF96 View Post
How do you show that someone can distinguish DUTs when he believes that he cannot?
As mentioned before, a good start could be to set up a listening test without revealing the effect under test.

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A good scientist would not tell lies in such a test, but how would the tester know?
Normally it is not a matter of lies; basically it (at least as a underlying hypothesis in these discussions) is a matter of "uncontrollable" bias.

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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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?'.
While that seems to be plausible, it seems that a strongly biased scientist will never accept any unwanted listening test result.
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Old 18th December 2012, 10:54 AM   #31553
DF96 is offline DF96  England
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Originally Posted by Jakob2
While that seems to be plausible, it seems that a strongly biased scientist will never accept any unwanted listening test result.
Perhaps that explains why some people seem so unwilling to risk offering an unwanted listening test result; they don't want to embarrass the scientists, as they know that scientists are delicate individuals with large egos who don't like to be proved wrong by experimentally established facts. To protect the scientists, they selflessly forego all opportunities to confim that they really can hear what they claim to hear.
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Old 18th December 2012, 11:13 AM   #31554
Jakob2 is offline Jakob2  Germany
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Originally Posted by DF96 View Post
Perhaps that explains why some people seem so unwilling to risk offering an unwanted listening test result; they don't want to embarrass the scientists, as they know that scientists are delicate individuals with large egos who don't like to be proved wrong by experimentally established facts. To protect the scientists, they selflessly forego all opportunities to confim that they really can hear what they claim to hear.
Such a good demonstration about the effect of a strong bias. (SCR)

If you remember the short discussion on the "Fremer listening test results on amplifiers" then you will understand what i really meant.
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Old 18th December 2012, 11:14 AM   #31555
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Originally Posted by RNMarsh View Post
The 2SK152 device may still be around... just have to go to Texas to get it at InterFET Corp. They say the 2SK152 is same process as their IF1320 and IFN152. Also, same process as 2N6451,2,3,4 (process NJ132L). Thx-RNmarsh

The BF862 has a Yfs of 38mS @ 10mA and 10pf Ciss
The 2SK152 has a Yfs of 25mS @ 10mA and Ciss of 7.5pF

So the BF862 has a slight shade better gm to C ratio.

EDIT -The specs on IF site are 2X different in some cases, Ciss 15pF and Idss range of 5 to 20mA vs 9.5 to 45mA. Same is loosely interpreted.
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Last edited by scott wurcer; 18th December 2012 at 11:20 AM.
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Old 18th December 2012, 12:35 PM   #31556
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I might talk about the origin of the 2SK152, what it was made for, and why it has been considered 'special' over several decades.
In analog video recording there is a special area where the S/N limit is significantly based on the 'quality factor' of the input device.
When I was at Ampex up to 1970, the chosen device was a specially selected 2N4416, chosen for low 1/f noise.
Later, Sony, in competition with Ampex, made their own ideal part, the 2Sk152, for this application.
I saw the part highlighted in a tech mag as the highest 'Q' part in the industry, so I thought to use them for hi Z applications. Independent testing with a QuanTech noise analyzer showed slightly disappointing 1/f measurement, but I have recommended them over the decades for condenser microphone use. At least you can get the parts in a T0-92 leaded package, and that makes handling easy.
Now the BF862 has a slight advantage in 'Q' and maybe even 1/f noise.
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Old 18th December 2012, 01:26 PM   #31557
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Quote:
Originally Posted by RNMarsh View Post
The 2SK152 device may still be around... just have to go to Texas to get it at InterFET Corp. They say the 2SK152 is same process as their IF1320 and IFN152. Also, same process as 2N6451,2,3,4 (process NJ132L). Thx-RNmarsh
See 31544 post MCM says they have the sony part in stock . just saying regards.
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Old 18th December 2012, 02:27 PM   #31558
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Originally Posted by john curl View Post
I might talk about the origin of the 2SK152, what it was made for, and why it has been considered 'special' over several decades.
In analog video recording there is a special area where the S/N limit is significantly based on the 'quality factor' of the input device.
Yes they are both RF FET's that can be re-purposed to audio. The fo of the BF862 is 750MHz which makes it want to oscillate unless you take extra care. I'll bet the 2SK152 has similar problems.

I alreay posted on the Pass forum plots of the BF862 showing its almost total lack of 1/f.
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Old 18th December 2012, 02:48 PM   #31559
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I agree, Scott, BUT can you get it in a leaded device?
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Old 18th December 2012, 03:30 PM   #31560
bcarso is offline bcarso  United States
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Originally Posted by john curl View Post
I agree, Scott, BUT can you get it in a leaded device?
With that bandwidth you might have a bit of a problem even if you could.
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