technics CD機 class AA是代表什麼呢？

MASH = Multi-stAge noise SHaping，是一種常用於數碼聲頻上抑制躁音的技術。
Class A及New Class A 都是甲類放大，但發燒友一般嚮往纯A類(pure class A)，其他什麼 class AA或所謂new Class A已經是不正宗，只是Pure Class A好大食，以工作效率而言不易處理，所以便出現了變種的Class A或 Class AB，但緊記只有純A類是最好聲。
但據我所知，Technics 的 Class AA 並不是 Class A。
下文摘自Wiki:
Class A
Class A amplifying devices operate over the whole of the input cycle such that the output signal is an exact scaled-up replica of the input with no clipping. Class A amplifiers are the usual means of implementing small-signal amplifiers. They are not very efficient; a theoretical maximum of 50% is obtainable with inductive output coupling and only 25% with capacitive coupling.
In a Class A circuit, the amplifying element is biased so the device is always conducting to some extent, and is operated over the most linear portion of its characteristic curve (known as its transfer characteristic or transconductance curve). Because the device is always conducting, even if there is no input at all, power is drawn for the power supply. This is the chief reason for its inefficiency.

Class A Amplifier
If high output powers are needed from a Class A circuit, the power waste (and the accompanying heat) will become significant. For every watt delivered to the load, the amplifier itself will, at best, dissipate another watt. For large powers. this means very large and expensive power supplies and heat sinking. Class A designs have largely been superseded for audio power amplifiers, though some audiophiles believe that Class A gives the best sound quality, due to it being operated in as linear a manner as possible which provides a small market for expensive high fidelity Class A amps. In addition, some aficionados prefer thermionic valve (or "tube") designs instead of transistors, for several claimed reasons: