Bel Canto ref-m series.
Class D amps that are superior to all or most?
Recently, I have heard about some Class D amps that may be close to the best there is regardless of class. Certainly, this technology has been in development for decades. The main issue has always been the switching power supply. In this regard, I have taken notice of AGD. They have created a whole new power supply that “switches” at a frequency 100 times the normal silicon based MOSFET. The designer uses a gallium nitride based PS. Interesting, it is enclosed in the KT88 glass envelope that sits on top of his amps. I am aware of two more pricey amps that seem to be also at the top- the Solution and the Merrill. There must be others that compete for the title. After my thread, “Is there a SS amp that can satisfy a SET guy?”, I am still on the quest.
Don’t want to spend $50K!
Don’t want to spend $50K!
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Oh SO "blah". "Sound quality and music enjoyment–wise, the LKV Research Veros PWR+ amplifier sits on a higher mountain than any other class-D amp I've encountered. It seems like Bill Hutchins made a slew of listening-inspired design decisions which, in concert, led to this extraordinarily natural-sounding power amp. I will be surprised if it measures super-low THD-wise, but, rest assured, I smiled contentedly every minute it was playing music in my room." "Today, most commercial loudspeakers feature reactive, low-impedance loads. Why? Because watts are cheap? Unfortunately, cheap watts often sound like crap watts. Fortunately, Bill's watts sound like limitless, sensual, tactile, luxury class-A watts. On the speakers I used, the Veros PWR+ put minnows, crappies, and my favorites, bass and catfish, into the once-empty class-D pond. Gleefully recommended." |
but many hear some thing not quite right with Class-D in the upper mids/highs with many speakers, and this is it’s Achilles heel.Complete rubbish. I've explained this many times on multiple threads. Its apparent that faced with facts, George is at a loss; his comments are far too inclusive. The output filter will have an effect on phase shift in the audio band **if the feedback is insufficient**. So if you see a class D amp that has lots of phase shift in the audio band now you know why. To prevent phase shift you can do it two ways: have loads of bandwidth (that's how we do it in our OTLs, by going well past 100KHz at full power) **OR** by using enough feedback that phase shift is corrected (which is in excess of 35dB). Some class D amps that switch at 500-600KHz sound great and others do not. Its very much like the difference between a type 45 SET and and 750 watt behemoth push-pull tube amp- they are two different things and sound different as a result. Class D in general is no different in this regard. The last paragraph is really terrible. You don't 'throw a load of feedback' in an amp to fix the amp, you throw a load of feedback in the amp to *fix the feedback itself*. There is a profound difference; to start with you can't just keep adding feedback as you need gain in the amp to do that and each stage of gain degrades the phase margin of the circuit. So it requires a bit of finesse. To get the required amount in a class D, you have to resort to self-oscillating circuitry (which is also helpful for keeping noise down as opposed to a zero feedback class D design). As a challenge to George: why not work out the oscillation criteria and get back to us here? If you can't don't feel bad, just allow the lesson to sink in that there is far more to this than you think! |
https://ibb.co/gt4qW9x Challenge your self, nothing I said was aimed at you, yet you took it to heart, wonder why. Whatever, your new class-D will tell if it’s remotely equal to the better high A- biased linear Class-|A/B amps, if it ever sees the light of day. |
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