I've been waiting since October to access the 4HV forum, but apparently things process slowly there, so I guess I'll ask some questions here. I think it would be pretty cool to have a low voltage, small, possibly musical coil. I found a company that sells high voltage transformers used in their neon sign testers. They operate from 110V and output roughly 50kV. The transformers are 1100 turns secondary and 10 turns primary. I haven't measured resistance and inductance yet, still waiting on my order to ship. For the output, these are pretty small. They are relatively inexpensive, and I think they are a better starting point than a much larger ignition coil or TV flyback. Power source, ideally a small 1P2S (7.2V) Li-Po pack. The normal circuit of the ETP tester is basically a 110V "doorbell" with the transformer connected in series with a special 0.15uF capacitor, and that combination connected across the normally closed contacts. As the current builds in the magnet coil, eventually the contacts open and the field in the magnet collapses giving a nice high voltage on the capacitor, charging through the coil. When the contacts close, the cap is connected as a parallel LC circuit with the primary of the transformer. The magnet coil and contacts work for loose definitions of work.. It's pretty inefficient, they limit use to about 10 minutes. The magnet coil is about 70 ohms, so I expect it gets pretty toasty after a while. The transformer is supposed to be resonant around 500kHz, which I will confirm when my order finally arrives. The only other complication that I am aware of is that the secondary is tied to one of the primary leads. I don't know if they are marked, or if in the end it actually matters much. I'm having trouble seeing how to efficiently replace the action of the mechanical contacts. I "could" rewind the magnet for 7V possibly, but that would be just a buzz and no music. All the tesla coil pages I've seen are for bigger and bigger power, where I want to be around 5-10 watts at most. The tesla coil pages I've seen stick with high voltage drive, not less than 50V so far, and typically 300+. I'd like to control the drive by microcontroller so that I can change the operation by firmware, and experiment with the shapes of the discharge. Apparently if you ramp up the output slowly, you can get longer "sword" discharges as opposed to thin ones when you just go straight to full power. A desktop or "pocket" musical coil is interesting, I think. I've seen the OneTesla but it's back to the high voltage high power approach. Any suggestions? Ideas where I can find viable low voltage low power drive ideas? --=20 http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .