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Class D Switching Power Amplifiers and Power D/A conversion

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Old 19th August 2005, 04:53 PM   #21
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IMHO, getting the THD in class D anywhere near class A or AB is a serious challenge right now.

The way I see it , anyone going to class D does so for the superior power capabilities, and uncomplicated scaleability. You just increase the supply rails, add parallel MOSFETS and go up in power
Most of us need a lot of power for bass frequencies.
So why not biamp, and let a good class AB take care of the mids and highs, and use class D for frequencies below 100Hz.
This way you can stop worrying about distortion, PWM frequency and HF noise in the output.

MOSFET turn-on and turn-off delays, rise times and fall times, and mismatches and asymmetries between these delays among components of the same bridge, coupled with temperature dependence of these timings, leading to more asymmeries, will for the foreseable future plague most attempts at "pure" unfeedbacked digital class D.

It will make clean, crisp, 20KHz response quite elusive for a while, until we make better MOSFETS.

Adrian
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Old 19th August 2005, 06:18 PM   #22
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Hi,

That's mostly all wrong too.

If you think it's that easy to scale switching amp up in power, I dare say, try it. Maybe at your 100Hz sub amp sure, but you're right there it won't work well for the highs.

The reason I wouldnt' bi-amp with a class A/B is because I wouldn't want it to ruin the smooth, airy, dynamic, natural sound of the class d in the highs where it also excels in performance.

You've clearly put zero research into this.
EDIT: At lest not in the last five years.

Regards,
Chris
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