no additional data is required to achieve perfect (in the literal sense) representation of the sine wave through sampling
Actually
any signal band limited to the sampling band.
I suspect the 'amplifier' problem has been studied, the design compromises have been made and it's now available in a monolithic packages from a dozen different manufacturers.
In a way, yes. Monolithic amplifiers can be very good and have excellent performance/price ratio. Discrete amplifier designs are still almost always crap that simply won't last (e.g. class AB output stages with Ube multipliers )
In commercial applications class D is extremely important, too, of course. Not just for low end applications, but also for high-end applications. Today you will often find that even ICs designed for low end markets incorporate not simply PWM modulators but actually quite good SDMs. Class D can surpass 0.005 % THD+N today (actually, ten years ago, but let's not nitpick on time lines).
I was wondering about that...
When I looked for amplifier ICs on TI's website there were no class A/AB chips for anything over about 5W. All their power amplifiers are class D. "Class D" is even in the category title for their power amp section ("Mid/High-Power Class D Amplifiers")
I haven't really been paying attention lately but I guess the world has moved on from when class D was only for "subwoofers and cars", and gone are the days when amplifiers were designed around their heatsinks.
Unless you're an audiophool, in which case heatsink design is alive and well:
[img]http://1.bp.blogspot.com/-4JF1O3qiPuw/T3HSCnB_P5I/AAAAAAAAB_o/mQqip-lN-5A/s1600/Pathos%2Badrenalin%2B3.jpg[/img ]
nb. I'm not knocking the sound quality of class A/AB amplifiers, it just seems like newer technology is making them obsolete.
Ah, their parametric search has a few bugs. TI still has a few AB power stages in their lineup, namely LM3886, LM3875, LM3856, LM4780 (=Two LM3886 dice packaged together). They also have a few HV input stages (LME49810, LME49811, LME49830, LM4702, ...), but I think they're starting to discontinue them.
I don't think AB is obsolete just yet, for two reasons. First, class D has become very, very good, but still can't quite reach the best linear power amplifiers. Second, audio PAs are quite often found in laboratories as cheap drivers for stuff - in a laboratory people might not like the additional EMI introduced by a class D amplifier -- although it's inside (inter)national regulations.
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As I mentioned above 24 bit DACs mostly make sense when you do digital volume control by scaling the PCM stream, which is a quite common thing to do.