My amps a custom hand built, point to point wiring, no circuit boards. customs wound transformers. Takes over 200 hours to build each. The frame is hand machined, milled and drilled by hand. These are the same type amps Doug Sax of Sheffield labs uses in his playback recording studio in Los Angeles. Four Tk88's put out 140wattRMS at .005% distortion levels. Very revealing and transparent.