Scooter, I'm not the OP, but will do my best to answer your questions-
1. The d:Vice MMA-A was specifically designed for use with the DPA miniature microphone line, and is the smallest high-quality recording arrangement I'm aware of. In addition to the miniature omnis (4060/4061/4063, etc), DPA's miniature microphone line also includes their miniature cardioids and supercardioids. Most of those are intended for mounting to instruments, some are podium and choir microphones. Beyond proximity effect range those miniature directional tend to have somewhat reduced bass response, but sometimes that's just right, and other times I've had no problem boosting the bass a bit, as its there and smooth, just picked up with less sensitivity. I use those in my main open rig, but in combination with the omnis. For stealthing I like omnis and have not used the miniature directionals on their own, but others here at TS do and I like what I hear from their recordings. That's one option for cardioids.
2. Sometime after the introduction the MMA-A, DPA changed their standard microphone line to make it modular, with separate caps + choice of a few different microphone amplifiers, similar to the way Schoeps CMC line works. Most of those modular microphone amplifiers have a balanced XLR output requiring phantom power, but one is extremely compact and features and integrated cable terminating to microdot for low voltage powering. The capsule end looks more or less like a side-exit Schoeps active cable. Because all DPA microphones are pre-polarized electrets, even the larger line of capsules require only a low voltage supply to power them and don't require a high-voltage polarizing voltage from the microphone amplifier, which is the primary thing the NBox is providing. This amplifier allowed use of the main line of DPA microphones with the MMA-A. That makes for a rig consisting of microphone caps > mic-preamp-cable > MMA-A > phone. So that's another option for cardioids, supercards or any pattern offered by DPA, using their primary line of high-quality caps. This option will be about the same size as an active Schoeps setup at the microphone end, but with the smaller MMA-A in place of the NBox and a phone in place of the SD-card recorder. You can't power your Schoeps caps with the MMA-A though. It's only able to directly power pre-polarized capsules.
3. Recording in 32 bit float format will only be advantageous if the ADC doing the digitizing is a specialized multi-staged design capable of greater dynamic range. Either the recording app would need to be designed to work specifically with an outboard multi-stage ADC (which could happen in a followup to MMA-A) using a digital connection between preamp/ADC and phone, or the analog input of the phone itself would need to be a multi-stage ADC, but since direct analog input to phones was never great and is for the most part discontinued (Grrr, just give me a headphone jack so I can used wired phones without an adapter) the second option is a dead end.
By the way, it won't help in getting answers from DPA that the MMA-A was discontinued earlier this year. I haven't seen a new product announced yet (but some places that carried the MMA-A and still have stock have raised the asking price). If they come up with a 32 bit float version and/or 4 channels I'll be happy. Anyone hear anything about a successor to the MMA-A?
This is the first I've heard of the discontinuation of MMA-A. I never got on the bus, primarily because I really didn't want to give up two of the four channels I'm currently recording to DR2d, and secondarily because I'm not an iphone user.. but would've bought an older one just for recording use if 4 or more channels were supported. I'd be OK with a requirement for use with an external USB battery if necessary to power it and the phone in support of the additional channels if necessary. Will be watching for what comes next.
