Mark Lee

Just an observation - it looked like we're all a bunch of pyromaniacs for a moment there. Thanks Laaz for breaking that cycle!

Slowly dancing in a burning room - John Mayer

I stand corrected. The one I have in my kit has both (one at each end). My apologies. As for the answer to my question, a higher arc top will have more projection and a relatively oboe like tone when compared to a flatter arched top, which will have less projection and a more flute like tibre. think of it as comparing the projection and bark a vintage Stromberg Master 400 or De Luxe (whose tops are consistently between 1 1/4 and 1 1/2 inches high) to the beautiful voice of a D'Anjelico New Yorker or Excel (whose soundboards are rarely much over 1 1/8th inches). You read it here first.

If you know, why are you asking? If you must know, I use a 5/16 inch phosphor bronze allen key.

try telling that to Freddie Green. Besides, I'm sure there is a good reason they are called single or double ACTION truss rods.

Theres a thing called the truss rod under the truss rod cover. give it a quarter turn clockwise with an allen key and se how much that helps. keep tinkering with it untill your action is to your likeing. Personally I like high action, around 1/8 inches. it makes already loud guitars (I also have a SJ-200, along with an Advanced Jumbo) even louder.