Back on track..
I've just now bought some AT831B mics. If I connect them via their individual power supplies they work just fine but as I want to use them for stealth recordings I don't want to have to carry 2 power supplies and two one meter long cables.
To use those AT mics directly into a recorder providing 11-48V Phantom-Power in the way intended by Audio Technica, you'll need one of AT's adapters. AT makes two different adapters for doing this. Both have a miniXLR mic input and a full-sized XLR output and step-down the 48V Phantom power provided by the recorder to the voltage needed by the microphone (around 8-10V, not sure exactly, but it's in that range).
The official AT solutions:
1) The AT adapter you liked previously (AT8531)
http://www.audio-technica.com/cms/electronics/36396386c21b22ab/index.htmlA rectangular box-shaped device. That one has the advantage of powering the microphone with either P48 from the recorder or via a AA battery - so it can serve as both a Phantom-Power adapter and as a battery box. Drawback is that it's bulky and requires a patch cable between it and the recorder input. You'll need one of these for each mic.
2) An AT adapter probably better suited to what you want to do (AT8538)
http://www.audio-technica.com/cms/electronics/106ef905e9296f3a/index.html. It's a smaller barrel-shaped adapter you can plug directly into your recorder without a patch cable. This one does not include provision for powering via AA battery so it only works into a recorder or other device which can provide it with Phantom-Power. You'll need one of these for each mic.
Non-AT direct plug-and-play solutions:
3) The Audix and Superlux adapters linked above will
probably work, providing similar functionality as the AT8538. Their barrel format is similar and they can plug straight into the recorder. Not enough data to conclusively confirm, but they should work.
4) A "three-wire" battery box. This will have mini-XLR inputs and the 4.7kohm mod does not apply. These are not as common as
2-wire battery boxes but are not complex. Typically these are made as stereo devices so you'll only need one of these for a mic pair.
Non-AT solutions which require a cable re-wire mod (and probably a 4.7kOhm mod)-
5) Adapt the mic cable to a "two-wire" configuration. Two-wire adaptation makes these 3-wire mics compatible with other common 2-wire eletret mic gear including battery boxes, preamps, and/or directly into a recorder providing Plug-In-Power (PIP). The 4.7kOhm mod applies to 2-wire configuration and is recommended for high-SPL recording. For quiet, low-SPL recording the mics will have a lower self-noise without the 4.7k mod. Some 2-wire battery boxes and preamps probive a switchable 4.7k option built into them, but most have the 4.7kOhm mod housed within the stereo microphone connector body.
6) A Naiant PFA properly configured for will work. Physical configuration is similar to the AT8358. You'll need one of these for each mic. Consult with Jon (Naiant-owner) or the Naiant forum concerning configuration. Not sure of 3-wire powering options with these, but Jon adapts them to power all sorts of mics and they have many options. You'll need one of these for each mic.
7) The Naiant IPA. They have many options. Consult with Jon (Naiant-owner) or the Naiant forum concerning configuration. You can use a single IPA for stereo (2-wire), which requires a cable between the IPA and recorder. Not sure of 3-wire powering options with these, but Jon adapts them to power all sorts of mics.
8 ) Direct into a recorder providing PIP, with the caveats fanofjam noted above:
An option which has not been suggested is to purchase a recorder that supplies 'plug in power' (PIP) directly to your mics from the 3.5mm mic in connector jack. However, the problem with this option is that most of these recorders underpower the mics...while the mics may work they usually don't get enough power to handle the high Sound Pressure Levels (SPL) at a loud live music concert, so underpowered mics will distort when the sound gets loud. Some people have reported good results using a few handheld recorders that apparently put a slightly higher voltage through their 'mic in' jack than other manufacturers. I would caution you to do plenty of research though...you should assume that a recorder with PIP will NOT provide enough power to your mics to record loud music concerts.