Perhaps in deference to his historical subject, Josh Kornbluth dresses up a bit in "Ben Franklin Unplugged," his latest--and in some ways richest--one-man show at Theater J. In addition to trousers and white shirt, Kornbluth dons a wine-colored, Jacquard-pattern vest. More sartorial riches are to come: In the second act, Kornbluth actually dresses up like Franklin, which makes sense, as he claims that the whole inspiration for the show came to him one day while he was staring into the shaving mirror and realized he bore a resemblance to "the first American." Jewish and the son of Communist parents, Kornbluth thinks that he might be described as an "un-American," so he approaches his research into Franklin with some trepidation. Soon, however, he has found a link between himself and his subject. "I'm a professional son," he confides to us, and his shows have always been about "my father's expectations for me and how I haven't met them."