SP link to your mic/pre didn't work, but if memory serves you have the SP-PASM-2, I think. In which case you don't need an adapter. The SP-PASM-2 has a stereo mini plug, and your JB3 accepts a stereo mini plug. Plug it in, power up the mic/preamp, navigate the JB3 to start recording and see what happens!
From the Archival Info Forum's
Newbie Central thread:
Usually, manufacturers who create devices which perform more than one or two functions [1-5] have to skimp on quality to keep costs down. Take the Sony D8 portable DAT recorder: in order to keep the costs down on the D8, Sony skimped on the quality of the preamp [3] and ADC [4]. As a result, many people use an external gain stage [3] and ADC [4].