People here seem to be confusing phantom power and plug-in power. Bear with me here for some background. All condenser mics need power. Original condenser types needed fairly high voltages, but most modern/affordable ones are "electret" types where one electrode membrane is pre-charged. But they still need power for a small amplifier at the business end, usually a single field effect transistor (FET).
Phantom power is a way of powering microphones that are connected via a balanced line. A balanced line is very good at rejecting interference because the input amplifier at the other end looks for the difference in signal between two signal wires from the mic. The signal wires are usually twisted together closely in the cable. There's a separate ground, usually in the form of an outer shield. Interference picked up on the two signal wires affects both in the same way, but a balanced input only passes on the difference signal. It ignores the common interference signal. This is called "common mode rejection". Phantom power exploits this. It places a steady voltage between both the signal wires and ground. Usually 48v, fed via two closely matched current limiting resistors. The mic circuitry can use this 48v for power. Meanwhile, the desk/recdorder/whatever input doesn't "see" it, because it's only taking the difference voltage on the signal lines, the common +48v DC, along with any common AC interference, is simply ignored.
So Phantom Power - usually 48v but sometimes 12v - is for balanced inputs, that is a mono channel with two signal wires in a twisted pair, and one ground wire. Most often terminated with an XLR connector, but sometimes (especially in mixing desks) using 1/4" "stereo" jack plugs.
Balanced connections are good for long cable runs. Any mic designed to run on phantom power needs to be tolerant of a 48v common mode supply.
Lavalier mics usually have some kind of short cable to a belt pack or other recording gear input. These mics also need to be powered, but they typically (not always) are unbalanced connections with a single signal wire and a ground, and they use "plug-in power". This is typically 2.5v (ish) to maybe 7.5v. Sennheiser lavs are spec'd to 7.5v. Generally, the higher the supply voltage the more dynamic range, but there are limits, and the mic's built in FET might not like much more than 7.5v. Cheap lavaliers (or other types) with their own battery, or a battery box adapter, might run from as little as 1.5v. Most laptops will supply about 3v or less for plug-in power, most "other" equipment probably 5v at most. Note that more volts does not always mean "more power", that's really not how this works. More headroom, maybe, louder signal, but only if you're not overstepping the design limitations. A mic designed to function properly on 1.5v is not necessarily going to work better at 7.5v, in fact it might distort at that voltage. It's certainly not going to enjoy 48v.
Plug-in power is supplied differently to phantom power. It's an unbalanced scheme. The way it works is that the mic connection has voltage applied between signal and ground, and, inside the plug-in-power-supplying equipment - laptop, camera, bodypack - a DC blocking capacitor passes the signal through to the preamp. A capacitor will pass AC (the signal you want) but not the DC "power" component, that would otherise swamp the front end of your equipment amp.
The RØDE VXLR+ type adapters convert balanced +48v phantom power to +5v (ish) plug-in power. In the adapter there's circuitry to convert the +48v common signal from the desk or recorder to +5v for the mic, and a DC blocking capacitor, and circuitry to present the returning audio signal as a difference between the balanced lines.
The RØDE VXLR+ is kind of pseudo-balanced on the XLR side, the "Pro" version features a transformer arrangement to present a proper symmetric balanced differential audio signal, hence it works with long cable runs (on the XLR side) like any balanced mic. Hint: only buy the Pro version if you use XLR mic cables rather than plugging it straight into a recorder. Sennheiser's version of the same thing is designed to provide +7.5v plug-in power for their ME4 and similar lavaliers, presumably for more dynamic range and headroom, though those mics work very satisfactorily on the much (much) cheaper RØDE adapters.
If you made up an adaptor to connect an unbalanced mic between ground and one of the signal wires on an XLR (or 1/4" jack balanced input) then turned on phantom power, the mic, expecting between 1.5v and 5v, maybe 7.5v at most, would be looking at 48v across it. Moreover, this would set the amp input at a 48v DC offset, which is very unlikely to do it any good.
If you wire the unbalanced mic between the two signal wires, then it won't see the 48v at all, unless you connect one of the signal wires with ground (in which case you'll short one side of the 48v through its current limiting feed resistor, again leaving a largish DC offset).
The quick and dirty way to get +48v phantom power into a 5v unbalanced plug-in power mic involves a DC blocking capacitor on the signal side, and a resistor that will form a voltage divider with the feed resistor on a signal line. Things like the RØDE adaptors are a better bet.
I came here looking for info on the precise pinout of RØDE's minicon-2 3.5mm TRS jack adapter for one of their lavaliers - I have some cheap Chinese 2.4GHz radio mic bodypacks and I get annoying hum pickup using the RØDE 3.5mmm minicon adapter plugged into one. The adapter expects plug-in power and works fine on the plug-in-power input on a standard Zoom H5 XY mic capsule, and outputs the same signal on left & right, while the lavaliers that came with the bodypacks (that are not such good microphones) provide signal on left only (tip of the connector, I think). So I believe the bodypack is supplying plug-in power on the connector tip, and perhaps just not connecting the ring, leaving the unbalanced stereo lead to the Røde mic susceptible to picking up noise from the digital circuitry in the bodypack.
Obviously the information I'm after isn't here, but I thought I'd try to clear up some of the confusion over phantom power and plug-in power!
