The better XLR adapter
 

I only ever hear about the beachtek XLR adapters, or the MA-x00 adapters. Which of the two provides the cleanest sound? I can snag a brand new MA-200 for $275.

The Beachtek is passive, as is the Studio One and Signvideo. They should not introduce any noise (except perhaps for that coupled in from stray magnetic fields), but will have some insertion loss.

The MA-100/200 provides about 6 dB of gain, and because it is not passive it may add a wee bit of noise, but that is insignificant. It cannot accept line level signals.

in other words the MA-x00 can't accept line outs from say, a concert mixer feed?

The MA-x00 starts to clip at about -7 dBV input level, and normal line level from a serious mixer is +4 dB. Many mixers have an option for mic level output which is typically -35 dBV give or take. This is OK. Altenatively you can obtain an in-line attenuator. Shure and others make them.

And if the run is short and the electrical noise environment modest, you could forego the MA-x00 and run a unbalanced line from the mixer's tape output jacks (if it has them) setting the XL1 to line input.

Andrew, what I use is the Sound Devices MM-1. It gives me phantom power, decent headphone monitoring (with volume control), very high quality pre-amp, and line level out. The line out (about 6 inches) goes directly into the RCA line in. At times I use an attenuator cable, that Don speaks of. This allows me to go into the XLR connections on my MA-200 should I need 4 channel audio. The cable is available from sound Devices and Shure and others.