And of course we can all hear 400+kHz, right? Yeah, right...
The Future of Audio Amplification
I have recently paired an Audio Research DS225 Class D amplifier with an Audio Research tube preamplifier (SP8 mkii). I cannot believe how wonderful and lifelike my music sounds. The DS225 replaced an Audio Research SD135 Class AB amplifier. Perhaps the SD135 is just not as good as some of the better quality amps that are out there, but it got me thinking that amazingly wonderful sonance can be achieved with a tubed pre and Class D amp. I have a hunch that as more people experience this combination, it will likely catch on and become the future path of many, if not most audiophile systems. It is interesting that Audio Research has been at the forefront of this development.
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Maybe the question we really should be asking Kosst and George is this: What, exactly, are the audible effects of switching distortion in a Class D amplifier, and can you give specific examples, with speakers, that you have heard this from? Like all amps, I don't think Class D is right for every speaker, so I am open to the idea that certain speakers will perform worse than others. So, George and Kosst, ball is in your court. Please share with us your experiences. Best, E |
Wrong!!! look at it and think again. It’s Stereophiles, there’s your hint, they’ve NEVER EVER given a Class-D 20khz square wave, as it would look unrecognizable as a square wave.You are correct and I was in error- that is a 10KHz squarewave. So that makes the scan frequecy in this example only 200KHz(!), which means the class D in question had to have been built in the **1990s**. By the early 2000s, everyone was doing well over 300KHz. That means that the bump on the leading edge is the phase shift caused by a filter that is likely at only 40KHz. So using this as an example of **all** class D amps is still a Hasty Generalization and like any logical fallacy, is false. 20kHz is hard for any amp to do, much less well???I agree- but the Pass amps IMO are some of the best solid state amps made :) Our OTLs are quite good at 1 watt 20KHz squarewaves too. And they don't care about the Litz wire; I'd be shocked if the Pass amps do! Regarding distortion- I agree wholeheartedly that small amounts of particular kinds of distortion are easily heard. This is why I've avoided feedback in our amps; while feedback suppresses distortion in doing so it adds some of its own, and its all IMD and higher ordered harmonics which are easily heard. But it is also true that you can build a class D with zero feedback and there are a number of them around. At that point, the limit of the distortion becomes the precision of the encoding scheme. For example if you use Pulse Width Modulation using a triangle wave to set the switching frequency, the distortion is all about how precise the triangle wave is and the speed and offsets of the comparitor circuit used. It happens that with that sort of circuit, as the amp approaches full output, it can have a form of soft clipping as the encoding scheme starts to fall apart. So the resulting amp can have very low distortion and a lack of higher ordered harmonics over most of its range. |
So that makes the scan frequency in this example only 200KHz(!),Wrong again when have you seen an amp that can do 200khz, have a slewing audio frequency square wave like this, the sides are collapsing in like the leaning tower of pizza Our OTLs are quite good at 1 watt 20KHz squarewaves too.And that is where you should stay linear and with tubes, otl, even add trany coupled, so your not hamstrung to certain speakers. You built your rep on them and now your going to destroy that?. Not a good move, it will come back and bite you on the arse, your just another respected amp manufacturer saying "give me some of that class-D action" |
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