Adcom GFP 750 (good) at about $700 =/- used, or Muse Model 3 Signature (significantly betters the Adcom) at about $2300 new (you will not likely find it used). The BAT SS pre amps like VK40 I believe have it, and the tube units have the unity gain as posted above - be sure to ck features on the specific model you are looking at. It is a great feature if you only have one listening/HT room.