it seems like literally every stereo amp performs bad
You have to take these detailed measurements of amps, DACs, etc. in context.
The "audiophile" press is small, and is directly sponsored by the industry via paid advertisements. Therefore Amir and other independents who perform these kinds of measurements are performing an important service to the community and to the industry at large.
Amir takes the most detailed measurements possible with his equipment, and that's important for science and transparency's sake. However, that doesn't mean small differences (or even some large differences) are necessarily audible.
Consider the following:
- Unless an amp is damaged or is being pushed to the point where it distorts heavily, your
speakers will have far more effect on your system's sound than the rest of the signal chain... by orders of magnitude.
- Unless an amp is damaged or is being pushed to the point where it distorts heavily, your
room will have far more effect on your system's sound than the rest of the signal chain... by orders of magnitude.
- Unless an amp is damaged or is being pushed to the point where it distorts heavily, your
speaker placement within your room will have far more effect on your system's sound than the rest of the signal chain... by orders of magnitude.
- This is a big topic, but some types of distortion may sound subjectively pleasing to many folks. Obvious example is even-order harmonic distortion exhibited by many tube amps, but there are many others.
- Your room will probably have at least 40dB of background noise, and sounds over 90dB are well into "bad for you" territory, so the effective dynamic range we really "need" from the signal chain feeding our speakers could be said to be only around 50dB. More dynamic range and less distortion is definitely better, but consider that next time you're comparing amps whose SINAD differs by a few dB.
- When Amir points out anomalies at 20khz or higher, that's interesting from an engineering standpoint but not directly audible unless you're a bat. At 30-40 years old, you're lucky to hear anywhere near 15khz, and your limit is quite likely below that.
The reality is that just about any amp you can buy, including a lot of cheap class D amps, and certainly including a lot of $100-$200 class AB home theater amps, will sound pretty darn good. You can have a very good sounding system for a few hundred bucks even if buying new... even modest bookshelf speakers can sound darn nice with proper positioning (typically, this means on stands a few feet away from a wall, but will be different in every room)
I'm sure that some will see this as a criticism of detailed measurements such as Amir's. Nothing could be farther from the truth: I'm a fan... this work is a huge boon to the community.
Better-measuring gear almost always
will sound better to some extent.... sometimes to a large degree, and sometimes to a miniscule degree. Just don't think that you need to chase down gear with jaw-dropping measurements to have a good time.