Exporting Audio from Tascam DA 78 or 88 to PC

To do it digitally, you'll need a computer interface with TDIF (Tascam Digital InterFace). There aren't too many that have it.

There's the MOTU 2408mkIII:
http://www.zzounds.com/a--3778/item--MTU2408MK3

Alternatively you could get a format converter box to translate TDIF to a more common digital interface like ADAT optical. There are lots of computer interfaces that have ADAT:

http://www.silentway.com/interfaces

The 2408mkIII translates TDIF/ADAT as well (even working as a standalone unit with no computer). There are smaller, cheaper dedicated TDIF/ADAT translator units too but they don't do anything else.

Or, you can do it via the analog i/o, which is easier but you lose a bit of quality.

For the lowdown on all the cables for this,
http://www.silentway.com/definitive-dtrs-guide-chapter-1-equipment-overview