Papa Nelson
I got a pair of 2sk77b. Wonder which design is best for it?

Best Regards

Is there a typo in the schematic, or is it just my ignorance showing early in the morning?

The cap to the left of 4N37 is labeled 10K. Should that be a 10K resistor? Or is it 10uF cap? I notice one of the two 10uF caps on the right is listed as 10K as well.
Joined 2012
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No typo as far as I know. The cap to the left of the 4N37 is labeled 1K (1000uF) and the cap at the speaker output is labeled 10K (10,000uF).

I have built this circuit with those values and it works and it sounds great. Not with 2SK77B of course, but with THF-51S.
Official Court Jester
Joined 2003
Paid Member
I expect that he will come up with a very amusing name for whatever they become.


well , in this moment it seems it'll be either slightly Babelfished iteration of what you did show in BAF 2015 lecture ( with input buffer implemented in biasing, servo - still thinking about) , or it'll be some big bstrd with inductive load

however , no hurry ....... pleasure is in entire glass of wine , not just final felling in da belly