Krell FPB600 can it be bridge to mono

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

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

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

I don't think you could delay the signal so the initial plateau biasing can stay in front of it, without recording and playback either by digital or tape means, this would be even more detrimental to the sound quality.

Back when I was building those water cooled class A monsters in the 1970-80's. My then boss and mentor Steven Deratz invented and patented the first electronic sliding class A bias system, it was good but never out performed the real thing.
After a few years he let the patent run out. Then I believe the first commercial system I saw of the same, came from Technics and many years after Krell bought theirs out.

Cheers George

Krells class A plateau biasing network, is not as good as normal high biased or pure class A, to spell it out simply.

1: The network senses the transient and raises the class A automatically to keep the transient in class A.

2:It then keeps that class A level for a few seconds just in case there's another transient following or not, if not it dies back down to Class B

3: The trouble with this system of sensing and raising is that the initial transient that comes along has long gone through to the speakers before the network has had a chance to raised the Class A. So it or the first part of it still in class B

4: So your not hearing the initial transient in class A it's B, and that's why this system will never be as good as normal class A biasing but then you get the continuous heat problem with that, and much larger heat sinks,

I use to water cool my heatsinks jackets, it was the only way for me to get 150w pure class A without the size and weight.

Cheers George

All the amps that I know that have been bridged, you gain big time in rms wattage, but loose out also big time on damping factor (bass control)

Cheers George