Wow! Back in 1978 I designed and built a digital switching amp that used PWM for my EE senior project. The trick was to have symmetrical circuitry for the positive and negative voltages, so the quiescent power consumption was minimized. At the time there I was forced to use V-FET output devices, to get a fast enough output slew-rate. These were VERY pricy, so it's no wonder the amp costs $10,000. Fortunately, I got a set donated to me from the manufacturer. There were a few problems with the design: 1) Biasing of the symmetrical PW modulators was tricky and could drift. If they did, you couldn't direct couple the output, but needed to use an isolation cap. 2) You had to take into account for the RC time-constant of the output load for proper filtration. 3) You need a lot of EMI shielding in the design because of the radio frequencies generated. In effect, you use the output loading as a low pass filter to smooth the modulate Pulse-Width into an approximation of the original audio signal. I just through out this contraption in a major clean-up effort. This kindof makes me regret that decision. :^( I guess there is nothing really new in audio. :^D Gary
Digital Amplifiers?
What is a "digital" amplifier. Bel Canto has a new model, the EVo 200.2, which purports to be "digital". As an aside, this unit also has the widest dynamic range I've personally ever seen on any piece of audio equipment (1hz - 250khz). I've received some newer marketing info from Bel Canto but I am personally not an electrical engineer and thus, regretably, my understanding of highly technical audio information is limited.