I got around to buying one of the VT1000. It seems to work and I have run through my box of preamp tubes and power tubes. It is not difficult to generate high voltage from a DC supply. A switching step up converter can get a high enough voltage to run the test. However I believe the device works more on the heater and emissions of the cathode. I have used it to find matched triodes in preamp tubes, as well as to see how matched the power tubes are. Found a few bad tubes to test and so far I did not see any false good tubes. It is what it is. Perhaps a toy compared to the units that cost a few grand. The good thing, I have found some weak tubes that came stock in a few of my amps, replaced them with tested tubes that rated better and the quality of sound improved considerably. Also had found some of my power tubes I had used and for some reason holding on too for replacement in an pinch rated quite poorly and recommended to be replaced. If you only have one or two tube amps, this is not needed as you can just plug and listen. Since I have nine tube amps currently (JP-2C, MWDR, Roadster, TC-50, TC-100, RA100 head, RA100 combo, Mark V, Cali tweed) it makes more sense to manage what tubes I have on hand and what is in the amps. You still need to listen to the amp after tube replacement but so far I am happy with this thing even if it is a toy.