Back in the day, I used to build Class A directly heated triode tube amps for hi-fi. These are poo-poo'd by the self-styled "scientific" hi-fi community for their high THD specs. But it's important to think about not only how much distortion is happening, but where the distortion is happening. In super-simple triode tube circuits with no negative feedback loops, THD is pretty much linear to the volume. For small signals - the detail in the mids and highs - distortion is effectively unmeasurable.
The mainstream A/B transistors + heavy negative feedback architecture has the benefit of low manufacturing cost (no need to match devices when you just feedback the differences out) and good specs. But where does the distortion happen? At the Class A/B crossover point, somewhere in the first watt. Until the amp hits maximum power and clips, the WORST distortion is in the first watt, where all the small signals live.
To my common sense and my ears, this explains how good-spec amps can sound very harsh and cold, while bad-spec amps can sound sweet and warm. It's not "euphonic distortion", as the pseudo-scientists claim. Rather, it's that the warm amp is actually distorting less where it actually matters.
The mainstream A/B transistors + heavy negative feedback architecture has the benefit of low manufacturing cost (no need to match devices when you just feedback the differences out) and good specs. But where does the distortion happen? At the Class A/B crossover point, somewhere in the first watt. Until the amp hits maximum power and clips, the WORST distortion is in the first watt, where all the small signals live.
To my common sense and my ears, this explains how good-spec amps can sound very harsh and cold, while bad-spec amps can sound sweet and warm. It's not "euphonic distortion", as the pseudo-scientists claim. Rather, it's that the warm amp is actually distorting less where it actually matters.