While there are many off-the-shelf power supplies available that can provide a universal input voltage and 12V output voltage, they do not provide the same performance as the J2170B. Most switching regulators produce significant ripple at and above 100kHz. This ripple passes through the PSRR of the internal opamps, reducing the noise floor. While this may work in many applications, it is less than ideal. Typical switching power supplies and even typical linear regulators have a high output impedance at 40MHz, due to the ESL of the output capacitors and the nature of the control loop.The Picotest J2170B uses a discrete design approach, offering very low output impedance, stable performance with large ceramic decoupling capacitors and ultra high PSRR compared with typical off-the-shelf devices. To maintain a good noise floor for various measurements, the power supply must have very low noise.