Don, a number of manufacturers are using switch mode power supplies in their class D amps because they are small, very fast, extremely energy efficient, and when properly executed yield wonderful musical results. Others are staying with traditional toroidal or linear power supplies that are a lot bulkier. Like with everything else, the difference is not so much in the underlying type of technology being used, but in how it is being implemented. A switch mode power supply is small and very agile, but it can also sound a little brittle when not done right. There are low cost switch mode power supplies for consumer level products. . . and there also very advanced and costly switch mode power supplies that are fast and quiet enough for aerospace and defense industry applications, that are used by some audio manufacturers in some reference products.
In the end, use your ears. . . if the amp sounds right to you, whatever the designer did with the power supply design must have worked. . . if it does not sound right, no matter the power supply technology used, the amp will remain unsatisfactory to you.
On the subject of break in, some manufacturers do a little burn in of their products before shipping. This is usually done as a final quality check. . . essentially to give the amp a chance to prove that it can perform its job. But the real break in process usually last hundreds of hours, and a manufacturer does not have the resources to lock its inventory for 6 to 8 weeks to do a complete break in before shipping. So, when you get an amp, and a switch mode amp like Spectron, be very patient and let it blossom. My suggestion is about 1200 hours to be safe, but some amps do take half as much. G.
