i just wanted to show my preferred setup for a medium current JT circuit that can be used in my case for a badass flashlight from an AA that uses up to 10 bright white or similar LEDs that might be able to put out about 15-20 lumens depending on the LEDs you choose. i would have strung 10 but ran out at 5.
circuit draws up to around 100mA and can push up to around 80mA.
the larger jt circuit i show using the big transformer is a good example of how the core can actually be too big for transferring high frequency current, because the more the draw is increased and the slower the pulse, the more current is being sucked in per pulse, coming in at a constant, and pulsing out stronger in bursts. the small ferrite spool core works great but if it were a little bigger would probably work even better.