So the merit is still on the components themselves , the topology
does in fact bring nothing more than other schemes , wich is expected
despite claims of the contrary.
Actualy what would be helpfull are measurements but to this date
we have seen none...
It's not just about current low Z feedback, it's all about input stage and its topology. To my opinion both signals modulation has to be done on one single (compound) super part where error is managable at uV region. We have basic tested and very reliable topology in every sense, we just have to perfect it. 
Trust me measurements are in second plan and they are here just to follow plus confirm the topology is correct. Idea is much more important also experiences from practical testing and listening sessions. As long as modulation is performed on a single "super part" I would be near.
Diamond buffer as subtraction node is not an option. Never like them anyway, tend to be 'nervous' at HF and the sound is consequently 'erased' like.
Yes it is, its the best option from a technical view. Nervous at HF and sound is erased Im sorry to say is nonsense and there is no evidence for this. Its use allows one to use feedforward which cancels nonlinear capacitances of the buffer. It also allows higher gain and the reason its use has higher performance compaired to a amp like yours. It also solves many temperature drift related problems.
If thats not a deliberate copy I dont know what is.
Apex seems to have a sea of ampliers which are all disguised copies.
Yes, nothing new, but I found many things while working with it. I got some very important experience, including coloring, imaging/soudstage, fatiguing, and all of them easily set.
CFA for me means a few things
1. Unlike VFA, no interposing current source fed LTP stage which sets the maximum current available to charge Cdom. This at once makes Classic CFA designs simpler (one gain stage only) and removes the LTP HF pole (usually very high freq but there nevertheless)
2. The feedback is of the voltage sensing current type into a low z feedback summing node. This is in contrast to VFAs where it is of the voltage sensing, voltage type
3. The feedback current directly modulates the TIS current after subtraction of the input signal ( no LTP), and if associated circuit parameters are correctly set, can result in TIS input currents significantly higher than available in VFA designs. This along with the above mentioned points, supports higher slew rates and bandwidths, albeit at lower loop gains (this is a single amplifying topology, unlike VFA).
Caveats: I am talking about conventional MC VFA's and you can get around some of the speed issues by using MIC.
1. Unlike VFA, no interposing current source fed LTP stage which sets the maximum current available to charge Cdom. This at once makes Classic CFA designs simpler (one gain stage only) and removes the LTP HF pole (usually very high freq but there nevertheless)
2. The feedback is of the voltage sensing current type into a low z feedback summing node. This is in contrast to VFAs where it is of the voltage sensing, voltage type
3. The feedback current directly modulates the TIS current after subtraction of the input signal ( no LTP), and if associated circuit parameters are correctly set, can result in TIS input currents significantly higher than available in VFA designs. This along with the above mentioned points, supports higher slew rates and bandwidths, albeit at lower loop gains (this is a single amplifying topology, unlike VFA).
Caveats: I am talking about conventional MC VFA's and you can get around some of the speed issues by using MIC.
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Why not make it simpler.
CFA is non VFA. It is one or more of single device or single enhanced devices amplifying, means simplest, quickest, more flexible, more stable, no major design rules and technique (In VFA it is always differential input pair, Miller Compensator, TPC, TMC, ...).
Bonsai,
I'm confused. Are you referring to the first stage of a CFA as a TIS? How can that be?
Cheers,
Bob
Lets make it like this. TIS with feedback is CFA. So there is no misunderstanding.
Lets keep things realistic, the diamond is used because it it is better in all circumstances and options, not dependant on any overall system. There isnt any cook recipe either. Its the choice of Opamps manufacturers and with good reason.
It's a bit more nuanced than that Ontoaba. VFA also fits your description!
If we take conventional VFA and conventional CFA (as I have assumed in my previous post above) then the distinctions are quite clear. However, they blur with the topology enhancements and under certain operating conditions. For example if you replace the conventional CFA TIS with a beta enhanced 'VAS' type or you run the CFA at high closed loop gains.
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Ok, no food recipe, but not always better in technical view is better sound. There is some other technical results that decreasing caused by increasing of other technical results.
For example faster configuration also gives lower gain. And in this case, bjt has its own sound characters that could be minimized with enhancement.
Is that similar with a differential input pair of VAS that using resistor to feed their emitter instead of using current source? and this resistor value is just too low.
This is why I asked about Jfet inputs. I was thinking the FE of this amp had potentital
http://www.diyaudio.com/forums/diyaudio-com-articles/194809-burning-amplifier-ba-3-a.html
Don't worry it is techincally measured, but it is usually covered by major measurements, because it just a very small phase most in damping timing. That is why it depend on overall circuit.
No, an LTP fed with a resistor is still an LTP and does not change the fundamental operation. Of course, if your current setting resistor is too low or too high you will have problems, but I am not talking about those conditions here.