slightly off-topic, but the SBM-1 doesnt like it when you split the s/pdif to a M1 and none M1 recorder simultaneously. if you do, the M1 will continually loose signal.
I've noticed this with multiple SBM1s running M1+D8, M1+MOTU interfaces and M1+M-Audio interfaces.
the non M1 units retain their s/pdif signal, but you will have problems with the M1