I'd either go with a Denecke PS-2 phantom > Denecke AD-20 preamp setup or Edirol UA-5 modded. The UA-5 is a preamp and phantom power rolled up all in one. Its the same size as the ART Phantom II. You can also run an optical cable between the UA-5 or Denecke AD-20 and the JB3. Most importantly, make sure you record with WAV when using the JB3. The WAV sound quality using either setup will kick your minidisc's ass. Healthy taper advice, put your MD on eBay and fahgeddaboudit!
Meters on the JB3 are pretty acurate when using either setup. I set my AD-20 to 4 o'clock.
Peace, bro.