Haven't pursued the 78 option primarily because of time constraints.
Basically, all I need to do is to feed the controller from a 15 volt battery source and I'd be up and running. The regulator chip can take about 35 volts, so if you had two 12 V batteries in series (for 24 VDC), you'd be happenin'.
The bigger issue I have is whether I consider this type of rig appropriate for 78's. There's only one way to find out, isn't there?
Variable speed - via trim pots ... this was one of the main criteria we had for our controller design. I know too many people who are pitch sensitive and want to be able to correct for mis-mastered recordings.
Jim Hagerman has just submitted a prototype to me of a 3 speed controller. I need to start beta testing it. I consider Jim to be one of the unsung heros of audio.
The intended arrangement is for me to distribute the controller - assembled, tested, and supported by Jim. We're probably 6-8 months from anything final.
Cheers,
Thom @ Galibier
http://www.galibierdesign.com/prd_quattro_alu.html