One of the greatest and invaluable tools you can have when it comes to loud tube amps or recording. It allows you to dime the master volume of any amp and get that organic tube saturation, but at whisper volumes. The PS-100 has two channels with separate EQ controls that are footswitchable as well as an effects loop and bypassable emulated XLR out. Well worth the money and in Excellent to near mint condition.