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Beast with a Thousand JFETs
Beast with a Thousand JFETs
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Old 6th September 2009, 12:59 PM   #121
R-K Rønningstad is offline R-K Rønningstad  Norway
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Quote:
Originally Posted by jacco vermeulen View Post
Thanks, at last someone with too many p-channels in their stock.
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Old 8th September 2009, 09:31 PM   #122
R-K Rønningstad is offline R-K Rønningstad  Norway
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Quote:
Originally Posted by Nelson Pass View Post
BTW, I have a batch of Sony 2SK82 and 2SJ28's coming in.

Does anyone know the pinouts on them?

NP, did you ever try these during the early Threshold years, when the Yamaha and Sony VFET amps first arrived at the scene? Or was these transistors totally inaccessible then?
And is this batch of Sony VFET transistors large enough to build 100 F-something amps with VFETs?


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Old 8th September 2009, 10:13 PM   #123
Nelson Pass is offline Nelson Pass  United States
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Beast with a Thousand JFETs
That remains to be seen. I doubt that there are that many.

I did not play with them back in the 70's, but it looks like if
I want to be Lord of the JFETs, I need to include them in my
collection.

There are even more surprising devices in store....

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Old 8th September 2009, 11:17 PM   #124
Michael Rothacher is offline Michael Rothacher  United States
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Beast with a Thousand JFETs
...And one JFET to rule them all.

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Old 8th September 2009, 11:43 PM   #125
ra7 is offline ra7  United States
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Beast with a Thousand JFETs
Lord of the JFETs... and MOSFETS... we bow to you.
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Old 9th September 2009, 04:13 AM   #126
R-K Rønningstad is offline R-K Rønningstad  Norway
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Tnak you, Nelson!
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Old 9th September 2009, 05:24 AM   #127
R-K Rønningstad is offline R-K Rønningstad  Norway
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Default Vfet

I meant to say "thank you" of course.

The VFETs was the possible holy grail in the 70ties, lots of promise, but even though VFET-sympathizer today hold e.g. the Yamaha B1 in high esteem, I doubt these are a match for todays better amplifiers. But could almost 40 years old devices like these VFETs still hold? Maybe - the 300B still is a very good tube, and if one can get the Toshiba 2SK146 that is still a good input JFET for a MC-preamp (I think John Curl used these in the early 80ties (JC80)).

Anyway (meanwhile, back at the ranch...) , NP, back to VFETs, wasn't it true that these required very special/complicated driver stages? And they were quite vulnerable, especially compared to the then new Hitachi power MOSFETs. So they disappeared from the scene.
Could you perhaps tell us more about your views on VFETs - pros and cons and all that?

Best regds
RK
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Old 9th September 2009, 07:27 AM   #128
wrenchone is online now wrenchone  United States
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I have a board sitting in my bedroom with some paralleled J110s cascoded with a MOSFET, intended to drive a load through a transformer. No way is it anywhere near as ambitious as Nelson's JFET monster, but maybe I should finish it and give it a spin. Maybe a more ambitious construction could be done, as I have lots of J110s. I was thinking of a B+ voltage of 150-160V, just using a rectified isolation transformer.
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Old 9th September 2009, 02:47 PM   #129
carpenter is offline carpenter  United States
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Beast with a Thousand JFETs
Got a schematic? Your project sounds interesting... I've got something like 500 j310s. They're dirt cheap.
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Old 9th September 2009, 03:06 PM   #130
Nelson Pass is offline Nelson Pass  United States
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Beast with a Thousand JFETs
That's the spirit.

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