John Curl's Blowtorch preamplifier part II - Page 1981 - diyAudio
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Old 16th January 2012, 06:26 PM   #19801
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My listening experience in touring both The Show and the CES. Years before, Waviac had a really good sound, a few years ago, LAMM had great sound, this year, I found nothing that 'knocked me out' Even JBL failed to show what they showed, last year, which was pretty darn good.
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Old 16th January 2012, 06:50 PM   #19802
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Okay, so maybe all the speakers sucked and the preamps were awesome. Or maybe the people setting up the systems forgot how. Or maybe the rooms were bad. Well, lots of possibilities ...

At a Stereophile show I once heard a setup with the Thiel speakers and a particular amp which I didn't think was good, for whatever reason. Being a Thiel fan I blamed the amp, of course. Months later I read a glowing review of the amp in Stereophile ... a bargain at it price.

Well, who knows why the system sounded bad. Lots of possibilities.
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Old 16th January 2012, 07:15 PM   #19803
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It was Wavac, not Waviac. Sorry.
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Old 16th January 2012, 11:19 PM   #19804
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John,

Do you still use 2sk147/2sj72 (I won't even imagine there are 2sk146/2sj73 left around) in the Vendetta front end, or have to use 2sk170/2sj74 now.
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Old 16th January 2012, 11:23 PM   #19805
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Of course, we use them.
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Old 16th January 2012, 11:34 PM   #19806
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john Keeps stock of these old Fets for his work including prototyping/repair of Vendetta if he wishes i suppose. He along with Erno are keeping these treasured Gems
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Old 17th January 2012, 12:12 AM   #19807
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My phono input uses matched 4 x 2SK147 and 4 x 2SJ72 per channel plus cascodes - bought them from Erno 20 years ago in the golden age of jfets. What is left for designers today ? BF 852 and waiting for Linear Devices to make a P channel device or do we go over to the dark side and use bipolars. Any sign of a surface mount N or P dual low noise jfet pair or is it all cell phone and computer chips and we are doomed to trolling Hong Kong Ebay sites for fake jfets forever?

Last edited by ticknpop; 17th January 2012 at 12:16 AM.
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Old 17th January 2012, 12:17 AM   #19808
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I am failing to see why you could not parallel 2 times 2SK170 and 2SJ74 each to replace one 2SK147 and 2SJ72 respectively. According to the datasheet I end up with the same total gm / input capacitance ratio. What am I overlooking, other than that k170/J74 are also becoming rare? Are there other parameters where they differ still?
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Old 17th January 2012, 12:42 AM   #19809
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2sj74 is also discontinued device. While diy guys can find, beg, borrow, steal, unsolder from a neighbour's amp while he sleeps, enough for a personal project not enough around to match IDSS for a manufacturer to build a new design from unless you are Nelson, Charles, or Constellation and were wise enough to stock up on singles and dual jfets to last a few years (hopefully).
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Old 17th January 2012, 02:40 AM   #19810
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curl, check ur PMs...
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