What To Do With Those 2SJ28's

[Michael Rothacher]

The one on the left almost looks like a transplanted smaller part or Russian SIT, tho that seems far-fetched.

 

[Michael Rothacher]

On the other hand if the J27 is a complement to the K76, then the one on the left fits that description. Any one know which part is was complementary to?

 

[PSz.]

J26 is the complement to K76.

 

[Michael Rothacher]

Thanks, then the one on the right makes more sense as a J27.

 

[cwtim01]

Thanks all for the answers. So I need to figure out what these six trannies are

They look authentic from the appearance, not many transistors are under this form factor, even less P-SITs, and they can take 200W of heat without problem (when mounted on a heatsink with cooling fan).

 

[Michael Rothacher]

From what I gather, they were only made in small sample quantities, so it may simply be that there was just a good bit of variation and these are from different selections.

 

[WalterW]

That's an extremely rare VFET! Indeed the complementary of the big 2SK77. Which was never used by Yamaha in production amplifiers.
You'll have to find a pair of 2SK77 and you can build a very nice push-pull amp

 

[cwtim01]

Stupid me , I made a mistake in the connections (power reversed between D and S). After correcting the mistake, the new ones give similar curves as the old ones

> You'll have to find a pair of 2SK77 and you can build a very nice push-pull amp
That's something I've been trying for 2 years without success. Some 2SK77 did show up in Japan Yahoo Auctions but the price was way too high. I had a vendor in China who's been searching for me at much lower price, but he only found me some J27 recently instead.

 

[Michael Rothacher]

There we go

 

[Zen Mod]

 

[jostwid]

What to do with those 2sj28

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.

 

[woody]

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 ?

 

[Michael Rothacher]

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.

 

[woody]

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.

 

[Michael Rothacher]

The output impedance is the drain resistance in parallel with the drain load. Where are you coming up with 20 Ohms, woody?

 

[woody]

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.

 

[Michael Rothacher]

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.

 

[Michael Rothacher]

The drain resistance is the slope of the curve, or the change in drain voltage over the change in drain current.

 

[woody]

Thanks, I had evidently done that calculation wrong before.

 

[Telstar]

Looks like the SIT-3 is coming very soon