John Curl's Blowtorch preamplifier part II - Page 3149 - diyAudio
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Old 15th December 2012, 12:11 AM   #31481
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Originally Posted by john curl View Post
I once built a 250W/channel power amp with a slew rate greater than 1000V/us. It CAN be done, if you care enough to do it.
Mine is only 140W
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Old 15th December 2012, 12:16 AM   #31482
bcarso is offline bcarso  United States
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Are the fet numbers of any interest? I know the rep, and could ask.

jn
They appear to be about the same as these Fairchild parts http://www.fairchildsemi.com/ds/MM/MMBF5461.pdf, although some have noted that sometimes Fairchild's semis seem not quite as good as some others (EUVL prefers the NXP J111 part in SM to the Fairchild, and in that case the NXP is rated for a higher breakdown voltage). So I don't know if Central's parts might not have some advantages.
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Old 15th December 2012, 01:20 AM   #31483
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They appear to be about the same as these Fairchild parts http://www.fairchildsemi.com/ds/MM/MMBF5461.pdf, although some have noted that sometimes Fairchild's semis seem not quite as good as some others (EUVL prefers the NXP J111 part in SM to the Fairchild, and in that case the NXP is rated for a higher breakdown voltage). So I don't know if Central's parts might not have some advantages.
I question if they have their own fab or are another test and rebrand operation, after all that's how we started.
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Old 15th December 2012, 01:33 AM   #31484
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Related to old Motorola jfet #'s from the '60's. Ask Richard Marsh.
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Old 15th December 2012, 04:30 PM   #31485
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Now that everybody is really confused, the parts linked by JN are modern packages of REALLY OLD PARTS. In fact they are so old, that I originally developed the comp. diff. jfet input stage with their original packages back in 1971. They are referred to as LONG GATE devices. Some RF parts had a different topology, but they usually had other problems like early bias leakage breakover (8V or so) and they were a real headache if you put too many volts (below their rating) on them.
These parts were superseded by the NC and PS geometry by Siliconix, and later, National, etc. These are the J113 and J175 respectively. These became the first parts put into the Levinson JC-2, as a complementary differential jfet input, back in 1973.
Of course, these parts were put aside for the 2sk170 and 2sj74, and are still used today.
While many pine away at the loss of the Toshiba parts, LIS has been making j113-j175 pairs for quite a long time, and working on general release of their version of the 2sj74, so things are not so hopeless as one might expect. In fact, if I were to maximize my investment in quality jfets, I should sell now, while they are hard-to-get. '-)
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Old 15th December 2012, 04:46 PM   #31486
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Originally Posted by john curl View Post
While many pine away at the loss of the Toshiba parts, LIS has been making j113-j175 pairs for quite a long time, and working on general release of their version of the 2sj74, so things are not so hopeless as one might expect.
j113-175 are noisy and low Gm. They (LIS) have been announcing their version of 2sj74 for more than 3 years and still nothing. So I do not believe them. They also do not respond for sample requests. LIS is not perspective supplier.
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Old 16th December 2012, 02:07 AM   #31487
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j113-175 are noisy and low Gm. They (LIS) have been announcing their version of 2sj74 for more than 3 years and still nothing. So I do not believe them. They also do not respond for sample requests. LIS is not perspective supplier.
They've buried me in samples. I can't quite figure out the situation.
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Old 16th December 2012, 02:22 AM   #31488
wayne is offline wayne  United States
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The P samples I have from LIS seem pretty usable. The new LSK489 is up for me to look at next. It is 4pF input 1.5 nV N dual. Interfet also supplies low noise Japanese P replacements and many other mostly N types. Not cheap though.
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Old 16th December 2012, 03:03 AM   #31489
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A number of messages were lost, and I don't know the reason.
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Old 16th December 2012, 03:08 AM   #31490
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I have had fairly long talks with the LIS manager of these fets, and I would say that IF you went to a Burning Amp gathering, you MIGHT get some samples. I certainly got some, but I doubt that an e-mail request or whatever will get you very far. It has been a source of frustration for a long time. Previously, Kirkwood Rough worked as a consultant on the Pfet parts, but no more, so I do not now have any 'inside' knowledge, but my boss at Parasound has a pretty good relationship with him, as well as Constellation.
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