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I would like to start a thread on Class D, knowing that we have a resident expert (fumac) on it.
Class D amps (or PWM amps) have its output stage work like a switch. It was invented in the 1950s and never took off due to poor sound quality and lack of highspeed switching devices.
a few things happened in the last few years.
1. power electronics got a lot better, and mosfets can switch in mhz range.
2. the use of DSP allows noise shaping (pre-distortion) to improve sound quality.
The first successful Class A amp is the Panasonic SA-XR20 which uses the TI TAS PurePath chips. It was called Poorman's Krell when it was introduced. That series goes all the way to XR-70 (XR20, 25, 40, 50, 55, 57 and 70). you could get them for less than $200 in the US, which includes AV functions, 125wx6 or x7 power. pretty good for the money.
then you have T-amp, using Tripath's class D chips.
after that, you have a rebirth of the Class D era. |
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