This is a very nice Preamplifier that has been upgraded to revision status by Steve McCormack. Preamp includes a phono stage which has also been upgraded. It also has an external power supply. I will include a an upgraded power cord in the purchase. The serial number on the unit will coincide with the upgrades included by Steve McCormack. Any questions please fee free to ask. Works and sounds great I am only selling as I am going to have digital only system.