Krell anticipator circuits of the 1990s

@jaytor   I think you've probably been taken in by the hype, because if it could change the bias instantaniously it would indeed be 'pretty clever'.

@retiredfarmer   As in many cases, a manufacturer's first products are the purest, possibly because they are conceived without thought of saleability and profit.

As I recall it, the progression from the start in I think 1983 was: KSA50  KSA100, KMA100 - two bridged KSA100s essentially, KSA80 - replaced KSA50, [possibly a couple more], KRS100, KRS200.  As I recall that ended the pure Class A series by the late 1980s.  I still have KSA50 as well as my KRS200s, and a very good sounding amp it remains after 40 years.  All progress is not good progress.

@clearthinker I agree with you new is ot a given that it is better. The idea that technology has advanced so much I find interesting what is really new technology in amplifiers? Preamplifier s? Phono stages? There have been both forward and backwards steps in digital. Some components have gotten better. In my personal opinion the levinson 33h s i have, got better with the new caps better than the original ones. I think powercords have got much more balanced in the last thirty years. The hifi receptacle s are much better than the hospital grade which were much better than standard receptacle s. Things have progressed but not everything and the old top of the line new product s are still contenders and the new ones have to be really good to be as good. The only amps that I have heard that I think are better than what I have or possibly are is a pair of de agustino mono blocks I heard in a store demo a couple years back they were there top dog at the time and were really pretty wonderful. Very few times do I listen to a demo and think I could live with that system. This was one of the few times I could say that.

@clearthinker - it sounds like you have already decided that Krell's plateau bias technology is just marketing BS. I read through the patent in detail and, as an EE, I do think it's a clever approach and not just hype. Whether it really improves the sound quality compared to operating the same circuitry with a fixed class A/B bias, I can't say. But I was pretty impressed with the sound quality I got from this amp. When driving various Magneplanar and Revel speakers, I thought the sound quality was on par with the much less efficient Krell MDA-300 monoblocks that my FPB-300 replaced. 

When it failed after 20 years, I decided to trade it in instead of getting it fixed or I would probably still own it.

I like my Pass XA60.8 monoblocks a bit better (as well as my 300B SET amps), but my current speakers are a lot more efficient, my musical tastes have changed, and I generally don't listen at as high a volume as I used to. 

Perfectly stated @jaytor. +1

My favorite sounding Krell monoblock amplifiers to present day are the Krell MDA 300. I think the quiescent current per monoblock is 400 watts.🤒 😎

Mike