Just read the manual, and on page 18 it states" Do not use the extension cable for connecting the USB device to the USB port. Use of the extension cable may cause harmful interference.
A "thumb drive" will work as it is illustrated in the manual but an external hard drive like my Seagate which can only connect via an extension cable, not directly, won't work.
Not necessarily, it only states "Use of the extension cable may cause harmful interference.", it doesn't say it won't work or cause damage, I am thinking by the interference reference meaning RF that might be picked up etc.
