The Amazing Fet Circlotron by Mike Rothacher

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#123
Michael Rothacher said:
NP is correct. If you use 2SK170's, you'll need P-channel output transistors and you'll also have to reverse the polarities of the floating supplies.

It has been my experience that the N-channel output version performs better measurement-wise.
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I have just stumbled over this thread, which I realise has been quiet for a while. I normally build vacuum tube stuff; mostly OTL amplifiers, including a circlotron. But I'm interested to try building the FET circlotron. I know there's been a lot of discussion about the availability, or otherwise, of the 2SJ74 JFETs for the driver stage. What is the current status, I wonder? Is there any other p-channel JFET in current production that could be substituted? I would feel more comfortable not being dependent on the continued availability of obsolete components, in case of needing to replace them at some later stage.

Thanks,
Chris
 
#125
cnpope said:
I would feel more comfortable not being dependent on the continued availability of obsolete components, in case of needing to replace them at some later stage.

Thanks,
Chris
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Dear my professor!

I welcome you with a joy here!
That's right, this is trouble of mine, too.
What there will be, if in my favourite amplifier the last existing semi-conductor perishes?
I may start being sad.
Papa will be guesses some newer thing for us anyway though.
This circlotron thing for me very nice. For me this is like a jing-jang thing.
It doesn't matter, that in it is semi-conductor, or electron tube.

With the deepest respect:

Wacky Gyuri
 

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#126
flg said:
http://www.diyaudio.com/forums/swap-meet/161366-matched-toshiba-fets-sale.html
:Pawprint:
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Thanks for the link. It's good to know see that there still seems to be a reasonably secure source for the 2SJ74 JFETs. But still, this seems to be a bit of a stop-gap measure, since they are no longer manufactured. I'm not familiar enough with FETs to know the answer, but is there really not some adequate substitute in current production? It would seem rather extraordinary if it were the only one that could do the job.

Chris
 
#136
yeah I know that they were supposed to be giving out samples, but there is a big difference between giving out a few samples and making meaningful amounts of them available to the public for purchase. they list all sorts of fets on their site that you cannot buy unless you buy a large amount and they make to order. i'll believe it when I see it.

and by large amount, I mean beyond the scope of a GB on here. not cheap either if its inline with the compliment LSK170. dont get me wrong, i'm pleased they finally did it, but i'm not over the moon just yet
 
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