today's experiments

 I thought maybe I should try reducing the input capacitor to a "normal" value: maybe too much bass response was making the sound gritty and less-optimal, or whatever; maybe there would be little to no change, in which case, no need to keep the anomalously large cap value which I had simply copied from the (nutty) transistor circuit.  So I swapped in a 22n.  And functionality completely ceased!  Putting the big 10u electrolytic back in, the sound returned.  Strange.

So I take this as an indication that the circuit is very unstable, operating on the edge of ultrasonic oscillation probably.  I really need a scope at this point, but unfortunately, my scope is 1400 miles away in San Diego.  And wow, digital scopes aren't that cheap!  Didn't I recently see little digital scope modules from the Internet in the under-$50 range?  Not finding any such now, everything is well over $100, even for the plasticky toys.  Darn.  Still looking...

With or without a scope, one obvious measure will be small caps from plate to cathode.  Another thing to order, don't have any high-voltage caps in the pF range on hand.


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