What's up chaz... you'd need a converter. Which in turn you'd need a battery for a converter. Hosa makes a good one, Midiman I think makes one. I've been lookin' at a Hosa for a while. My Hi-MD takes optical, so I've always thought that it'd be good to have a converter for patching situations.
Hosa ODL-276
http://www.hosatech.com/hosa/products/odl-276.html
How would you connect, digitally, MD recorder to s soundboard? Would you choose to you this hosa device?
Only if the sbd has a digital coax output. I've never ran digital from a sbd. I'm sure it's possible if you have access to a digi-out, but I've never had access to a sbd digi-out. If by chance it has an optical out, there is no need for the converter. I've only ran analog out from a sbd. Hope that helps!