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What To Do With Those 2SJ28's
What To Do With Those 2SJ28's
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Old 11th October 2017, 09:37 AM   #271
jostwid is offline jostwid  Switzerland
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Default What to do with those 2sj28

[QUOTE=Michael Rothacher;5066108]Here are a few of my thoughts. In keeping to the "simple" criteria, I have traded some things like gain or voltage swing for fewer power supplies and so forth. This is my homage to Nelson Pass's homage to Richard Feynman

Here's the link:
Six Easy (P)ieces

#1,#2 The usual suspects in antimatter form
#3 A follower for light bulb lovers
#4 A little two-stager
#5 A potentially fun little circuit, SE/PP selectable
#6 An even simpler circlotron, for those who weren't crazy about all the supplies in the V-FETRON.

Hello
I am a bit late to the game.
As for me, the Sony SITs particularly shine in preamp duty. LuminAria was a revelation to me. Today i may consider to convert my L'amp to preamp duties.
This is what i have in mind: (Reference to Pass SIT3)

Sony SIT driving an autoformer, followed by SE, PP, DEF or whatsoever follower.
The SIT and autoformer shall easily provide 20 clean volts.
The Sony SIT will impart its precious sonic signature on the more neutral follower.
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Old 11th October 2017, 02:42 PM   #272
woody is offline woody
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What To Do With Those 2SJ28's
As it happens I also have a couple of 10lb roals of #16 wire so # 2 looks very interesting. But have a question? At about 24v and 1.2 A won't the drain resistance be ~ 20 ohms ?
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Old 11th October 2017, 06:58 PM   #273
Michael Rothacher is offline Michael Rothacher  United States
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What To Do With Those 2SJ28's
With 24V, you probably want an iron core, low DCR, coil like the 193V. If you want to use your big spool of wire, just raise the voltage to account for the extra DCR.
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Old 11th October 2017, 08:47 PM   #274
woody is offline woody
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What To Do With Those 2SJ28's
I have both a pair of 10lb coils of wire and a pair of iron core inductors. And if I used the air core inductors I would use a powersupply between 30 and 32 VDC . My major concern is what the output impedience of the amp would be and in amp # 2 wouldn't the output impedience simply be the drain resistance.
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Old 11th October 2017, 09:22 PM   #275
Michael Rothacher is offline Michael Rothacher  United States
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What To Do With Those 2SJ28's
The output impedance is the drain resistance in parallel with the drain load. Where are you coming up with 20 Ohms, woody?
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Old 11th October 2017, 10:50 PM   #276
woody is offline woody
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What To Do With Those 2SJ28's
I tried to just guess looking at the curves for a 2sk82 . On second thought perhaps my guess was way way off. Any idea about what the drain resistance would be for this device at 25v and 1.5A ? My concern is my speakers need to see a amplifier output resistance of ~10 ohms so I may be better just using something like a 10 ohm resistor as the load instead of an inductor.
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Old 12th October 2017, 12:32 AM   #277
Michael Rothacher is offline Michael Rothacher  United States
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What To Do With Those 2SJ28's
The drain resistance is around 8 Ohms. Assuming the inductor's impedance is >> at most frequencies, the output impedance is a little less than 8 ohms.

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Old 12th October 2017, 12:36 AM   #278
Michael Rothacher is offline Michael Rothacher  United States
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What To Do With Those 2SJ28's
The drain resistance is the slope of the curve, or the change in drain voltage over the change in drain current.
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Old 12th October 2017, 12:49 AM   #279
woody is offline woody
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What To Do With Those 2SJ28's
Thanks, I had evidently done that calculation wrong before.
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