The RCA out jack from the TASCAM is probably line level and it may overdrive the XLR input of your soundcraft board which is expecting a mic level input. Some mixer board XLR inputs can handle the higher level, you simply have to turn down the input gain or disable the pre-amp. A better way would be to go from your TASCAM RCA jack to a 1/4" jack on your board, assuming you have one.
As far as losing anything, their might be an impedance mismatch issue when connecting a line level output to a XLR input; I really don't know what the ramifications might be. If the mismatch is really bad, the usual results are distortion and/or an inability to get get enough volume.