Amplifier specs, does they matter?

^^That.

I would say the most important spec is weight within a given amp type. The amp with the best power supply and running the most in class A always sounds better and controls the speakers better imho. This means larger transformers, filter caps, and heat sinks.

Kijanki, you appear to have taken a stronger position against use of NF than in the past where you argued results were very implementation specific.

Or are you just pointing out pros and cons, which all approaches always have?

Based on a stated 100X improvement with NF, negative effects would have to be quite significant to eliminate that completely.

The "its all implementation specific" argument still seems to ring true to me based on what I see, read and hear.

At least one company claims that their really-fast negative feedback loops eliminate the problems traditionally associated with negative feedback. Maybe the situation has improved to the point that it can potentially do more good than harm.

Nelson Pass published an excellent article on distortion and feedback:

http://firstwatt.com/pdf/art_dist_fdbk.pdf

The bottom line is it does not seem to be implementation specific.

About 50 years earlier, Norman Crowhurst had some similar comments on feedback and showed that harmonics can be added up to the 81st harmonics, with attendant intermodulations at the point of feedback (the feedback node).

This document is an excellent read:

http://www.pmillett.com/tubebooks/Books/crowhurst_basic_3.pdf