Also, if one does not insist on a very low roll off frequency the use of film capacitors becomes mode affordable, circumventing electrolytic cap issues.
An intersting anomaly, the SSL9K DIY preamp gets away with 2.2uF input caps and large bias resistors. In theory it should be noisy and distort, but it does not seem to be an issue to users.
Some time ago a guy called C. Bates has published a study on capacitor distortion in EW. He claimed that two bipolar capacitors in series have as low distortion as most film capacitors. Of course that does not mean they "sound good" to most listeners, the source of endless debates.
However, technically it works out nice since most bipolar caps are rated 50V or less and you need to block 48V phantom power, you can use two 100uF / 35V bipolars in series and get a 50uF / 70V capacitance that has very low measured distortion and low chance of explosion.
Cheers,
Tamas
