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Old 2nd May 2009, 02:42 PM   #21
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Sorry about the 2SK222 I think BDENT had about 50-100 and they went fast after someone on Yahoo posted it. It's Sanyo and because it never caught the eye of the audio world there aren't a dozen folks on ebay selling them like the 2SK170. Also it's a low Idss thing for phantom powered mics where the minimal circuit has the FET at Idss. The J310's have the two little squiggles, I forgot if that was Vishay or Fairchild or what? They were from eBay, but guaranteeing the noise will be problematic on any of them. I managed to scavenge at SOT23-6 test socket at work for the BF862's. If you haven't checkout syn08's 32-BF862 phono stage a noise record (without magnetics) I think. Though he did have to use ferrite beads to suppress all that RF gm.

I plan to buy a bag of 500 or a 1000 2SK222's next time I'm at the Akihabara.
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Old 13th May 2009, 01:50 PM   #22
BFNY is offline BFNY  United States
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I received the BF862 and J310s, sorting the BF862s was not too bad after all. Used 2 pieces of adhesive copper foil for a fixture (and soldered wires to the foil). I found 40 seconds to be about right for 10V supply to get Idss.

The biggest surprise I had was the linearity of the J310 in a gain of 2-4 configuration with a health supply voltage(40V). I was looking for a no loop feedback simple gain of 2-3 circuit with voltage output of 1-2Vrms for a filter project where there is loss in the filter.

If preliminary results hold, the J310 delivers with nice results, gain of 2-3 with .008% thd kinda numbers at 1 VRms. Requires some tweaking though. I had a 5K resistor on top, 1k on bottom, load of 6.8k. A b1 after this would be an interesting line stage for those who need some more oomph.

Bob
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Old 13th May 2009, 04:25 PM   #23
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The current production LSK170's are great!
Somebody may still have some or maybe time for round two!
Also guess Linear is getting ready to release a complement soon!
Unless going for mic pre the 2SK222 that Scott mentions as
good sub, I personally don't know of anything that was
really better for audio.
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Old 13th May 2009, 04:26 PM   #24
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Group Buy: Linear Systems LSK389 / LSK170 JFETs (i.e. Toshiba 2sk389/2sk170 subs)
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Old 14th May 2009, 12:54 AM   #25
BFNY is offline BFNY  United States
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Quote:
Originally posted by coloradosound
The current production LSK170's are great!
... I personally don't know of anything that was
really better for audio.
It's really great for low level signal amplification where low noise and high gain is important. But the low Vp and high gain may work against it for other applications with line level signals. Even with a lot of degeneration. This point was made by Borbely in his first Final Frontier JFET article from 10 years ago when comparing the 2sk146 and 2sk170.
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Old 14th May 2009, 01:49 AM   #26
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Quote:
Originally posted by scott wurcer

I plan to buy a bag of 500 or a 1000 2SK222's next time I'm at the Akihabara.
Let me know when you're going and we'll plan an expedition. I think I still remember where some of the better piano bars are in the Shinjuku when I was doing banking.

Could be the second DIYAUDIO campout, after the burning amp just keep going west!
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