I have heard that there is a central Mumble or Teamspeak server for PA, but searching through the forum the only thing I can find is a server called 'Ten Forward' that seems to not have been used for PA since beta. Is the server some kind of closely guarded secret?
I don't know that there is a central one. There is an IRC chat but beyond that I think the main centers are clan voips. http://irc.lc/esper/planetaryannihilation
Pretty sure most clans would be happy for you to drop in and play some games over their TS, the details are mostly publicly available if you have a look.
I believe the PACE ts server is both quite large, and free to use for PA players (even though PACE is now disbanded the server itself was already paid for). @oathalliance would probably know more + the addy etc.
The Realm TS is the most active teamspeak with a large portion of its traffic being for PA out there.
Can you send me the ip? I've got a could friends in that clan, and that's the time zone I'm always online at.