Yes you can. Depending on the resistance of the adapter it may or may not play havoc though. I tried that for 3 trips on the 74 at my first establishment. Long story short, the pig-tail adapters rarely have the correct resistance for the system, and you and everyone with you gets to listen to an awesome constant squeal and whine on the ICS (it has something to do with proximity of your headset and/or pig-tail cables to the anti-ice in the windows, as well as the resistance in the ICS). It's all EE stuff that I never studied. I ended up getting the civil version of the A20.

HOWEVER if you're going to drop that coin, I personally recommend the Bose Aviation ProFlight 2 or the Clarity Aloft Pro Plus if you can handle the in-ear noise protection. More comfortable for long haul and has the right amount of noise protection for the 74 flight deck, which sits right at about 75-90 dB. The bluetooth function (they both have that option) is nice for the long haul flights as well. Yes it's expensive, but once your hearing is gone, it's gone. I saw it as a long-term investment in my sanity.

Whatever you do, don't be that guy who insists on using the crappy telex that's in the aircraft. Nothing like listening to a dude breath heavily with a nice static whine background then shout at you because he can't hear anything for 8 hours straight.