I have three pairs of caps, one pair each for parafeed (4.7uF Mundorf Supreme SGO) , interstage (0.1uF Jupiter Gold), and cathode bypass (47uF Mundorf Tubecap). None of them have a marked polarity that I can tell. My plan is to wire them all in parallel to each other and then run in series with 8.3 ohm 90 amp resistance to simulate the speaker and run off a single channel of a solid state amp.
I don't have any special CD to play. But I have electronic music that plays at the extreme ends if the audible spectrum.