To accompany my review of the Dan D'Agostino Master Audio Systems Progression monoblock amplifier elsewhere in this issue, I talked to Dan D'Agostino about the amplifier's design. I started by asking him what were some of the major differences between the Momentum and the Progression monoblocks?

Dan D'Agostino: I took the best parts of the Momentum's more sophisticated and complex circuitry and put them in the Progression, without using the same high parts count. Each stage of the Momentum's gain amplifier is separate, with input stage and driver stages on separate rails. All of the Momentum's devices are designed for maximum performance in a small package, which requires a lot more of them, and a significantly bigger input card than the Progression's. These differences create subtleties, because I'm able to run much higher current in the Momentum's front end.

I have always been fascinated by audio power amplifiers. I even tried building about a hundred of them. My best friend in high school, Bill Brier, taught me the basics of soldering, wire management, and reading schematics. He loaned me his Dynaco Stereo 70, and gave me a hot-running, 20W, class-A transistor amp that he'd built on his mother's kitchen table. Bill took me to concerts, and taught me about classical and jazz music. He had perfect pitch, tuned pianos for money, played every instrument in the orchestra, and had memorized the complete keyboard works of J.S. Bach before he turned 16. And this stuff was all on the side—mainly, we built drag race cars together.