Doc,
If I recall, the 9000-pro had a 1/4-inch input--not an XLR, but I may be thinkin of another keyboard. The 9000-pro was a great keyboard, and I know of one that is for sale, but it's here in the U.S.. And, as Dave said the technology is ancient by today's standards.
Most keyboards with a 1/4-inch input will accept a balanced connection via an adapter cable and not experience any decrease in either volume level or vocal quality. The right cable for the job has pins 1 and 2 of the XLR jumpered and connected to the 1/4-inch plug's shield, while pin 3 is the hot connection and connects to the 1/4-inch plug's tip.
Hope this helps,
Gary
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Travlin' Easy
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PSR-S950, TC Helicon Harmony-M, Digitech VR, Samson Q7, Sennheiser E855, Custom Console, and lots of other silly stuff!
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