[petek]

Jack,

Well.... it's working :-)

My only real concern was creating a ground loop, but the potentials at either end seem close enough that I'm not picking up any sort of problem.

If I get a free minute I'll see if I can figure out what the output of the box looks like (electrically). I'm guessing that one end is at a firm ground, the other going to the CD circuitry. Still... it's easier to boost the voltage if you don't reference the output to ground (heck something as simple as a diode / cap ladder or even simpler with a power astable into a transformer ... hmm... if you went ahead and referenced to ground you might even be able to do it with just a tapped primary ... then rectify it, through it into a 600 V / 10 uf cap then use a high voltage SCR to dump into the primary of the spark coil...)

So little time, so many neat things to investigate.