The Rolls Bellari PA555 Tube Preamplifier uses one 12AX7 tube running at 150 volts and has four switchable inputs. The input signal is connected directly to the grid of the tube and all of the gain of the PA555 is from the 12AX7 tube. The output section is a pair of emitter followers to drive the output. The PA555 has a no feedback circuit or integrated circuits in the audio path, it is all analog.All Bellari products are hand built in Salt Lake City, Utah by people who care about high quality music.How many times have we all heard the back-handed compliment about an audio component when someone says it sounds "really good for the money?" The inference is that even though it sounds really good, it doesn't sound all that good because it just doesn't cost as much as the high-priced spread. The Bellari PA555 doesn't just sound "good for the money." The PA555 sounds "good for any money."