Actually, this may help. Reading the manual I can see that the switch has 4 states.
PC-1(MAC), PC-2(MAC), PC-1(PC), PC-2(PC)
The PC-1 settings are 31.25K (bit/sec) and the PC-2 settings are 38.4K (bit/sec). Still, the difference between PC and MAC are unclear from the manual.
I would think for any chance of success withy the Amiga, the speed would have to be set to 31.25 so that the machine things its talking to the MIDI box. Would that be correct?
I'm pretty sure the SC55 does not have the serial port unless its an MKII model. I was also looking as SC55s before really deciding on the SC88pro.
Thanks.
I've got the same kind of PC/Mac switch on my Korg AG-10 (Cable:
http://www.korg.com/AG001 ). I've never tried it directly to my Amigas as I assumed a specific driver would be required. Never thought it might be just plain serial. Remembering the actual driver settings for the PC they did contain the standard Bits/Parity settings, but also things like SysEx, Aftertouch etc. Thus my assumption that there was a bit of proprietryness there.
My gut feeling is the switch just changes specific settings relative to the different serial implementations on PC and MAC 422 v 232, and is not much to do with the actual instrument interface.
Be interested if you get it to work. I don't use my Amiga for Midi NE more only MODs and then only listening.