Jax Taylor Served Divorce Docs From Brittany Cartwright While Filming 'The Valley'

Jax Taylor may be the No. 1 guy in the group ... but that didn't stop him from getting hit with divorce documents while filming season 2 of "The Valley" ... TMZ has learned.

Sources connected to the show tell TMZ ... the Bravo personality was served the docs from his estranged wife, Brittany Cartwright, while filming the new season of the reality show Tuesday.

We're told both Jax and Brittany filmed for "The Valley" Tuesday ... however, they did not film together -- which means a 3rd party brought the documents to the Jax's Studio City sports bar owner (and former bartender at the restaurant SUR).

Sources connected to the couple tell TMZ ... Brittany took the initiative and decided it was time to file ... since her estranged hubby has done too many things for a reconciliation to occur.

No word on what exactly went down between the former flames ... but sources say Jax is getting ticked off from all the praise Brittany's getting for choosing to file -- especially as he thinks Brittany has her own dark side to her.

Jax may not be the true villain in this split ... we're told all will be revealed when "The Valley" returns for its sophomore season ...  we've been warned it'll be a "heavy one."

Relationship issues aside, Jax and Brittany are simply focusing on their young son, Cruz ... who has their full attention now that the day-to-day chaos of their marriage is no longer distracting them.