Bernie,
When I got both the SD90 and the SD40 I discovered something strange.
The SD90 would NOT power a keyboard using a USB port and It required the 5 Pin
midi cable to work. I tried it with several midi controllers and AJ confirmed the SD90's USB ports did to supply enough power to power a keyboard. The SD40 does power a keyboard using the USB port.

I don't know what this has to do with this thread but thought it might be of interest to some.

Deane