Digital Amplifiers?

Funny you should mention PWM. Didn't Hitachi have a go at PWM amplifiers back in the late '70s, touting these things as "Class H" amplifiers? They never took off in the pre-digital stone age. What goes around comes around. Take the "network computer", for example... display and keyboard and just enough processing to paint electrons on the screen, but all the real smarts is in a server on the other end of a wire. Gee -- sounds a lot like a mainframe and terminal!

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

Hi Try to check this web-site http://www.tactaudio.com. Here you can read about the digital-amp technology. I have the digital Tact Millenium amp, so if you have any questions, you are velcome to e-mail me! Best regards Michael Ohrt Fernel