So George do you think that Dagostino's new amps are better being a class AB design? If you are right how does Gryphon maintain Class A in their designs? I don't believe them and think they are just AB designs.
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Looking at the size of the heat sinks of the new Gryphon's and the quoted Class A, I don't believe they could be pure class A, maybe sliding bias as well. There were ones going back 10 years that were huge and only 100watts total they could have been pure class A or 3/4 and the rest A/B. There's a lot of fudging going on with quoted class A figures. The only ones I know for sure, were the water cooled ones I built, and maybe the forced fan cooled early Krell KSA50 and KSA100 not the 100s And also a 20w Nelson Pass A40 project also a fan force little monster, from the 70's which was the basis of my 150w water cooled ones. [url]http://www.google.com.au/url?sa=t&rct=j&q=&esrc=s&source=web&cd=6&cad=rja&uact=8&ved=0CDAQFjAF&url=http%3A%2F%2Fwww.firstwatt.com%2Fpdf%2Fart_a40.pdf&ei=SKBnVYLoI4Xj8AXY5YPIAg&usg=AFQjCNFzV3J8CTmkP6fI6mreRC5uu3Ymaw&bvm=bv.93990622,d.dGc[/url] Here was one for sale one ebay. [url]http://www.ebay.com/itm/Nelson-Pass-A-40-Class-A-Stereo-Amplifier-A-Very-Rare-Classic-/291381081421?nma=true&si=ph3vIqnZtW%252Bz6wdpAIVab%252BCAJoI%253D&orig_cvip=true&rt=nc&_trksid=p2047675.l2557[/url] Cheers George |
I found Krell's patent on what is being discussed. It appears that rather than adjusting the bias among the different possible levels based on the input signal, the adjustment is performed based on sensing of the load current. Which explains the reference by Martin Colloms to "high-speed current-feedback circuitry." The patent goes on to indicate that bias increases necessitated by abrupt transients will be "jumped to," but subsequent decreases, if called for, will occur one level at a time, and slowly. So George is correct that in the event of a large and abrupt transient there will be some very brief instant of time during which the amp will not be operating in class A. I have no opinion regarding the degree to which that may be audibly significant. Regards, -- Al |
So George is correct that in the event of a large and abrupt transient there will be some very brief instant of time during which the amp will not be operating in class A. I have no opinion regarding the degree to which that may be audibly significant. I would say if your "good enough" and you have an aural microscope for an ear, you may hear the class B xover distortion which could manifest itself as a smearing, or hardening of the first transient after a quite section, if the plateau biasing has come back down from the last transient. Cheers George |
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