Krell anticipator circuits of the 1990s

Thanks for your posts.  I think so far 3.5 to 0.5 in support of my position.

@jew16384   You offer suggestions as to elements of the design that might be engineered with the objective of moving instantaneously from Class B to Class A bias.  (Put like that it sounds an impossibility).

You say ' Of the speed of the gain decision must be quick.'  Indeed it must.  What I asked is can it be quick enough to amplify a signal just heard in pure Class A.  i.e. to change bias instantaneously.  That is an impossibility.  The only way of doing it would be to buffer the signal and amplify it later. when the Class A bias had been achieved.  But that would entail all sorts of dither and clock distortions, turning an analogue signal effectively into digital when I wanted to listen to LPs.

A friend of mine has one of these Krell amplifiers, I think.  It has about 5 different ranges that are identified by lights on the front.  The example you give is very specific and it's almost always possible to find a specific example to expose a design flaw because every design has compromises.  The way I would look at it is that there could be something lost when the amplifier is first triggered to the next level and then anything within that level would be unaffected until it dropped down a level or was triggered to go to the next.  I would think that by watching the lights it would be possible to estimate the number of times that something was potentially lost during the initial instantaneous need to go up to the next level.  I think it's obvious that the sound would be expected to be something less compared to another Krell running wide open all the time, but there's reasons that make that design not ideal (though not released to the SQ most likely).

If it changed the bias in few milliseconds you will not know the difference. However can the power demand keep up, will it compress the dynamics in the outputs. The main reason for doing this is to save money in the power supply and lowering the weight and size of the chassis.
 

Example,  If a fiber is Cut on a long haul fiber network happen the system will switch to a backup fiber with in 50msec . ( telecom voice and data ) it has been proven that at most you will hear tick in that time period of 50msec to restore the path. The data is buffered and request a retransmission and it works.

In the long run you’ve added unneeded complexity to a simple amplifier to reduce cost those element I mentioned. Keep it simple stupid is the cry. But it can work, I never compared one type amp to another 🤷‍♂️

@jew16384

Yes it is unneeded complexity.

Note: I can't get a 'retransmission' of what comes out of the groove on my LP.

I don't think cost was a main motivator; look at the price of Krells until D'Agostino sold and the price of D'Agostinos now.  More like 'price no object'.  Neither was lowering the weight and size an issue.  Just look at today's big amps, even if they are all AB hybrids.

No, the green lobby was the big motivator as I suggest in my post.  That is why there are few pure Class A amps today and to my knowledge no really big ones.

I want the dynamics I paid for in my media (mainly LPs).  That's why I keep the KRS200s (in fact uprated to 400w/side for a UK Krell dealer, from whom I bought them way back.