|Nothing. It has everything to do with solutions designed to save money (vs. better solutions) though
not true.It is just a way and for some the best way,others not.I personally have and have built every manner of topology there is and at this point in life prefer the simple single ended class-a stage above all others on the sonic merits.It is a taste thing and no more
Back to Opamps and if discrete is better than chip amps or visa-versa
Chip amps are and must be a comprimised solution because they are a generic part and not a highly specialised part.The manufacturer can "suggest" uses but in the end they have no idea what you will be using it for so must design for just about any contigent over a very wide range of possibilities.
This is not inherently a bad thing but the limitations are WE have no access to the inner workings and must accept whatever parameters the substrate designer decided were best.
Sometimes this leads to a good sounding chip but even thenm is and must be a comprimise.
Next.There is no such thing as a class-A monolithic opamp and there can not be.the size of the package and heat dispersion alone would dictate a much bigger area (footprint) AND some means of heat sinking so right there is a huge built in comprimise since it is well known class-A sounds better and that is not just "hype" but reality
Not only are chip opamps not capable of class-A but some not even Class-A/B but are in fact Class-B amps though in the long run class-B may be a better choice than an imperfect A/B stage and here is why
Class-A : Output section transistors are always turned on full throttle so they do not have to respond to music signal but just pass them along amped to a new level.Unless this amp is fully balanced from input to output all the output section transistors will be the same polarity (All NPN or all PNP)
Class A/B : Output section transistors only respond to a signal of the same polarity as the input voltage so a positive going signal activates the "P" channel transistor and the negative going half of the signal activates the "N" channel part.This may sound OK in theory but the reality is there will be a "disconnect" at some point between the P and the N trasistors that is totally dependant on where in the range they are biased into class A and where A/B takes over.Because of the package size of the opamp the "A" zone is virtually non-existant.The chip could not cast off the heat so is not asked to and that means crossover distortion where the + signal goes to a - signal and the transistion zone between the N and P channel transistors are not in sync
The reason why most opamps use this method is because it is more efficient,uses less power and does not require additional heat sinking but NOT because it is a superior way.Cost savings,low heat generation no more.Not merit but cost
class-B : This is where the output transistor is either totally ON or totally OFF just like in class A/B.Where it differs is there is no "cross" to a polar opposite but like class A all the signal is handled by a single device (either N or P).It is like Class-a in that way but unlike Class-a which is always on full boogie ready to rock
class-B is off until activated by an actual signal.This may sound bad but in reality to me is a better way than AB though not as good as A.
Any real limitation will be at the leading edge
of an audio signal where it must go from "off" to "play" so if it lags a bit then the front end of a note will be slightly truncated but the GOOD NEWS is if designed properly all the notes will STOP at the same time since it will go to "off" as soon as there is no signal.
This means the lowest heat generation of all three types (most efficient) and no crossover distortion because the plus does not hand off to the negative
That is what a monolithic opamp IS.
Discrete Op-amps ARE superior because the user determines the mode of operation at each stage and can optimise each for both the position in the circuit and for end use.If that end use is music then fully class-a operation with no limits is not only a possibility but what every audio specific discrete opamp design I know of operates at !
So there is the "why" of my statement that a properly designed discrete opamp will whip the sh*t out of any monolithic opamp.they can and they do and the only reason to consider a chip amp is portable operation,heat generation or low cost but NOT because it has better sound and that is what all this is about right ?
Told ya I was gonna be bad but when I
am bad I am good !