This is truly a "Jack of all trades" STAX amp, with a voltage selector on the back meaning it will work anywhere with mains power, and a choice of normal bias and pro bias jacks on the front it will work with any STAX headphone (or "Earspeaker") from the last several decades. This amp. has been professionally rebuilt (I can provide receipts) last year, and then a few months later replaced with a STAX tube amp, so has had very little use since the rebuild, and is no longer needed. These amps sell on ebay for around the same price I am asking - but with 30 year old caps etc. still in them! I feel that makes mine very well priced, and a great way for someone to get into STAX at a very reasonable price without having to start with the lowest end gear. I've tried the new entry level stuff and it isn't anywhere near as nice sounding as this old amp. I'm asking $500 USD for this amp, buyer pays any fees, postage and insurance. I am also selling some nice STAX headphones (see my thread in the HP for sale forum) Will sell both for $850 USD, and I'll pay 1/2 the postage. edit: I'm located Tasmania, Australia.