BE55 PLT TOOK OFF WITHOUT TKOF CLRNC.

Narrative

I WAS TAKING A PLT FRIEND FOR A DEMONSTRATION RIDE IN MY ACFT. I WAS CLRED TO 'TAXI INTO POS AND HOLD' FOR TKOF. WHILE HOLDING ON THE RWY REVIEWING TKOF CHKS; TWR INFORMED ME THAT THERE WAS AN ACFT ON PRACTICE APCH FROM THE OPPOSITE DIRECTION; AND THAT ACFT WOULD NOT BE LNDG. I WAS LISTENING FOR TKOF CLRNC; BUT FORGOT THAT I HAD BEEN INSTRUCTED TO HOLD; AND COMMENCED TKOF. MY PLT FRIEND WAS HAVING DIFFICULTY ADJUSTING THE VOLUME IN HIS HEADSET. HE DID NOT THINK HE HEARD THAT WE WERE CLRED FOR TKOF; BUT THOUGHT THAT HIS RADIO VOLUME WAS TOO LOW AND SO HE DID NOT OBJECT. IMMEDIATELY AFTER MY TKOF; TWR INSTRUCTED THE ACFT ON APCH TO TURN R. WHEN I HEARD THIS; I INITIATED A R TURNOUT AS WELL. I DID NOT SEE THE ACFT ON PRACTICE APCH; AND DO NOT KNOW WHAT HIS PROX TO ME WAS. AT ABOUT THE SAME TIME; THE TWR INFORMED ME THAT I HAD BEEN INSTRUCTED TO HOLD ON THE RWY. I COULD NOT THINK OF AN APPROPRIATE RESPONSE. I IMMEDIATELY REALIZED MY MISTAKE AND WAS INSTRUCTED BY THE TWR TO CALL THEM BY TELEPHONE UPON MY RETURN; WHICH I DID. THE CTLR REPRIMANDED ME AND I APOLOGIZED. I OFFERED TO CALL THE PLT OF THE OTHER ACFT TO APOLOGIZE; AND TOLD THE CTLR THAT I HAD MADE A MISTAKE; WITH SOME EXPLANATION OF HOW IT OCCURRED. NORMALLY; WHILE WAITING ON THE RWY AFTER BEING INSTRUCTED TO 'TAXI INTO POS AND HOLD;' THE NEXT WORDS FROM THE TWR ARE 'CLRED FOR TKOF;' AND I WAS WAITING FOR THOSE WORDS WHILE PERFORMING MY FINAL PRE-TKOF CHKS. I BELIEVE THE TWR WAS BEING COURTEOUS IN EXPLAINING WHY I WAS HOLDING ON THE RWY; BUT I THINK SUBCONSCIOUSLY I TOOK THE WRONG MEANING AND PROCEEDED. BECAUSE OF THIS EPISODE; THE WORDS 'POS AND HOLD' WILL ALWAYS BE HIGHLY SIGNIFICANT TO ME IN THE FUTURE. I WILL LISTEN CLOSELY TO THE EXACT WORDS OF THE CTLR TO BE CERTAIN I HEAR 'CLRED FOR TKOF.' IN ADDITION; I WILL DEVELOP A PROC TO SET THE CORRECT VOLUME OF RADIO; INTERCOM AND HEADPHONES FOR R SEAT PAX. IF FLYING WITH ANOTHER PLT; I WILL ASK THEM TO QUESTION ANY ACTION WHICH THEY THINK MIGHT BE IMPROPER.