Obviously the guy got it used and/to flip or he would have known if it worked to begin with. May be completely shot or have channel imbalance.
The foam inside may be deteriorated?
No you cannot run it directly off a speaker amp without a Stax Pro Bias adaptor unit that changes the input signal voltage up to what the headphone needs= 580 volts.
These hook up to your amp's speaker terminals to get the signal from them and step it up ( SRD-7 Pro, SRD-7 MK2, WOO WEE )
Personally, without testing and confirmation that it works and also works without one side louder than the other, or any sort of driver buzz /rattling I ndefinitely would steer clear, unless you are willing to risk it.
But you still need to find a pro bias Stax Adaptor and they are not cheap, or a Stax energizer which is basically a small amp you feed the signal into.
So your total outlay costwise will be at least double what you pay for the headphones themselves. At LEAST. As squallkiercosa mentioned above also.
Price out the Stax energizers and adaptors first and you will see.
Edited by nick n - 12/8/13 at 2:42pm