Who's the manufacturer on those ones? Track them down via Google.
Also, is Soundcraftsmen still in business? I'd be talkin' to their service folks about replacements, and what the voltage SHOULD be on those caps. It's also likely shown on the schematic for that model.
Here, again, replace both caps, not just the bad one.
Sprague and Mallory make 15K at 75V, CDE has a 14K at 75V listed, and United Chem-Con makes both 10K and 15K at 100V. Same screw-terminal "Computer Grade," yes?
I'm just looking at the Newark paper catalog here. See them online and Allied, Mouser, others....
Panasonic shows a 10K at 100V at Digikey...