George:
"Every amp I know of also has Class-A input stages, and "why suddenly is the Class-A linear the preferred way for the input", why not for the output as well???"
Hello George,
I don't think anyone's claiming a class A input stage isn't an excellent typology for an input stage since the class A typology is well known for it's very high sound quality performance. At low preamp stage input voltages, the excess heat generated by the highly inefficient class A typology circuitry constantly being in operation is not a major cause for concern.
While the extremely inefficient class A typology for an output stage is also excellent for sound quality, the excess heat generated by the highly inefficient class A typology circuitry constantly being in operation is definitely a major cause for concern since it's easily able to significantly raise the temperature in a typical domestic room.
But you already knew all this, George, before you made your comment. My question is why, knowing all the above, you even bothered to make it?
Obviously, one of the major advantages of utilizing class D output stages rather than class A output stages is its electrical efficiency and resultant dramatic decrease in the amount of electricity that is wasted by simply being converted to excess heat. Class A is about 10% efficient and class D is in excess of 90%.
Class A amps are typically expensive, operate at very high temperatures,are very large and heavy due to the numerous, large and heavy heat sinks required in an attempt to dissipate the large quantities of excess heat produced as a result of their extreme electrical inefficiency.
Class D amps are typically less expensive, operate at much lower temperatures, are much smaller and lighter due to the their lack of need for heat sinks required to dissipate the very small quantities of heat produced as a result of their extreme electrical efficiency.
The difference can be demonstrated clearly by a raw egg. Drop one on a class A amp at peak operating temp and you'll shortly produce a fried egg. Drop one on a class D amp at peak operating temp and you'll just have a raw egg mess that will remain until you decide you may want to clean it up.
Besides the advantage of your amp not acting as an HVAC component, there's also the class D advantage of cooler operating temps likely resulting in improved reliability and longevity due to the well known principle that sustained excess heat is a major factor in electrical component part failures.
However, I believe an individual's amp choice is likely made primarily on the basis of perceived sound quality and price to performance ratios, with amp typology traits being less important to most. I think Class D amps need to be leaders on these two factors to achieve continued success.
Tim
"Every amp I know of also has Class-A input stages, and "why suddenly is the Class-A linear the preferred way for the input", why not for the output as well???"
Hello George,
I don't think anyone's claiming a class A input stage isn't an excellent typology for an input stage since the class A typology is well known for it's very high sound quality performance. At low preamp stage input voltages, the excess heat generated by the highly inefficient class A typology circuitry constantly being in operation is not a major cause for concern.
While the extremely inefficient class A typology for an output stage is also excellent for sound quality, the excess heat generated by the highly inefficient class A typology circuitry constantly being in operation is definitely a major cause for concern since it's easily able to significantly raise the temperature in a typical domestic room.
But you already knew all this, George, before you made your comment. My question is why, knowing all the above, you even bothered to make it?
Obviously, one of the major advantages of utilizing class D output stages rather than class A output stages is its electrical efficiency and resultant dramatic decrease in the amount of electricity that is wasted by simply being converted to excess heat. Class A is about 10% efficient and class D is in excess of 90%.
Class A amps are typically expensive, operate at very high temperatures,are very large and heavy due to the numerous, large and heavy heat sinks required in an attempt to dissipate the large quantities of excess heat produced as a result of their extreme electrical inefficiency.
Class D amps are typically less expensive, operate at much lower temperatures, are much smaller and lighter due to the their lack of need for heat sinks required to dissipate the very small quantities of heat produced as a result of their extreme electrical efficiency.
The difference can be demonstrated clearly by a raw egg. Drop one on a class A amp at peak operating temp and you'll shortly produce a fried egg. Drop one on a class D amp at peak operating temp and you'll just have a raw egg mess that will remain until you decide you may want to clean it up.
Besides the advantage of your amp not acting as an HVAC component, there's also the class D advantage of cooler operating temps likely resulting in improved reliability and longevity due to the well known principle that sustained excess heat is a major factor in electrical component part failures.
However, I believe an individual's amp choice is likely made primarily on the basis of perceived sound quality and price to performance ratios, with amp typology traits being less important to most. I think Class D amps need to be leaders on these two factors to achieve continued success.
Tim