NAP250 is a higher-end model, using gold sealed tubes as power output tubes, more milky flavor.
The cost of the product using audiophile equipment, such as the highly acclaimed 718 resistors, WIMA capacitors, Nippon NASS axial electrolytic capacitors, paired with the input tube for the F Fairchild BC546 beautiful sound small tube.
Suggested input voltage, plus or minus 40VDC, power not less than 300W cow!