Actually, I have been able to play Edison Diamond Disc records --
the heavy, quarter-inch thick (6 mm) jobs -- on a 1970s vintage KLH
four-speed player.  The secret is to

(1)  Use a _stereo_ cartridge (anything else will damage the record!)

(2)  Use the LP (45/33) side of the needle (my KLH has one "universal"
stylus that works fine)

(3)  Rewire the cartridge so the stereo channels add rather than
subtract in the vertical plane, which means the channels subtract
in the horizontal plane used for 78s.

I took the easier route of connecting a speaker between the two "hot"
left and right speaker terminals.  This lets you hear the difference
signal, which is the vertical or Edison signal.  I've been amazed to
find out how much deep bass is in the later Edison discs that were
recorded electrically, including a couple theater organ recordings.

Normally I just play my discs on one of my Edison machines.  I do
have "Kitten on the Keys" played by Zez Confrey himself.  Not as good
a sound, nor half the fun, of a piano roll though.  I loved the story
of the "human jukebox" at the Library of Congress.  Do they have Edison
discs too?

I agree that shopping the thrift stores and garage sales for a 78 RPM
turntable is the way to go.  Buy several, you'll find one that works.

Mike Knudsen