I have seven VVs, all mod boxes. My Big Daddy uses an evercool switching regulator, but all the rest (Little Sister, two Big Brothers from Ken, a Big Splash from Shan, and two Madvapes VV boxes) use the older, less efficient linear LDO regulator (I think they're all the Fairchild chip, but I'm not sure about that; some might be the TI version). I'm about to convert one of my two Phidias wood mods from a bottom feeder to a VV by installling the Madvapes Fairchild board where the feed bottle went.
Interestingly, I much prefer the older, cheaper, and less efficient linear regulators. They run 1.5 ohm dual coil cartos beautifully at any voltage from mid-3 to mid-6 volts. They also just seem to vape better than the evercool switching regulators, hitting harder and producing superior vapor. Switching regulators are better for increased battery life between charges. My Big Daddy, with two 18650s, seems to go for weeks between charges, but then I don't use it constantly. Other than that, though, I'll take linear regulators any day.
VV or 5-volt regulated PVs with current limiters built into the chip put an upper cap on voltage with 1.5 ohm duals. Darwin goes to about 4.5 according to owners' posts, ProVari shuts off lower than that. My Big Kazoo 5-volt regulated mod won't fire the duals at all, not ever, which aggravates me some, but it won't fire 2.0 ohm Boge cartos or LR atties either.
All of Ken's VV boxes have a rotating dial for voltage adjustment. The others have a set screw. I had felt before owning any VVs that I would hate the set screw adjustment (it does seem barbaric to have to carry around a jeweler's screwdriver, and that kept me away from the original Buzz). In real life, however, this turned out to be no big deal. In fact, there's a practical advantage to the recessed set screw---adjustment dials can and do get moved inadvertently just by handling the PV. You can turn the voltage way up or down accidentally, without knowing it. Now I'm in the habit of visually checking the dial setting on my Little Sister, Big Brothers, and Big Daddy, because I don't want to fry a LR atty or 2.0 ohm Boge carto by running it at 6+ volts.
Only one of my VVs has a built-in digital voltage meter---Shan's Big Splash. And I do love that. For the others, a standard VOM multimeter is a pain because of the leads, so I use one of the Madvapes digital meters that's encased in plastic with male and female 510 connectors on either end. That works fine, although screwing it on and off the connector is a bit of a pain. Some switching regulators and even some eGo don't work with the Madvapes meter because of their pulse technology. Linear regulators work fine, though---another reason I like them. Would I like the ability to read the actual resistance of whatever atty/carto I'm using? Sure, but I don't pine away dreaming of that. I KNOW the factory specs for all my atties and cartos, and my drip tips are color-coded to their ohm-ratings. So, the fact that you can put ANY atty/carto on a Darwin and not inadvertently kill it (because the Darwin senses the resistance and automatically adjusts the voltage to the user's dialed-in watts), well, that doesn't much matter to me. I've never yet fried an atty or carto with any of my VVs.
The dials on my Lil Sis, Big Bro, and Big Daddy have indented dots around them that pretty accurately reflect their incremental voltages. If I want 5.2 volts, I don't need a meter to check that; it's just past the fourth dot. 4.5 volts is right at the third dot. You get what I'm saying. In real life, this means that I'm likely to "fiddle with" the voltages on those units and change voltage much more often, because doing so is easy and fast. With both my Madvapes VV boxes, I tend to set them to 4.5 volts (a sweet spot for dual coils) and leave them there, simply because I need both a meter and a screwdriver to accurately change their voltage. So, yes, a built-in meter is a very nice feature, but the lack of one isn't a deal-breaker for me.
That said, I would highly recommend the Madvapes VV boxes. They provide a fantastic vape---kicking like mules. Battery life is fine with two 14500s (I'd guess 6-8 hours on a charge), and they're dirt cheap---how can you beat $38 shipped? Some folks don't like plastic box mods because of the shape or the relative fragility of plastic. I'm not among those dissenters. I love how the 3xAA box feels in my hand, and exercising ordinary care when removing and replacing the backs will keep their plastic tabs intact for years. I try not to drop them, but I have, and they've survived every time, so they're sturdier than some people assume. I'll probably buy a third one soon.
The artisan wood mod builders are making some nice VVs now. The Monkeyboxx VV is well designed, and Brian's Mark IV at Red Sky Mods is beautiful. But I'm not a bottom feeder guy anymore, and both those mods are awfully big and a bit bulky. I prefer smaller VVs. Another reason I love the Madvapes boxes.
I'm glad folks love their Darwins and ProVaris (and soon-to-be Eclipses), but I have no interest in acquiring any of those. I will check out the new Buzz Pro when it comes out, but I'm quite happy with what I've got now.
"obsolescence"? Never!
