The story goes that audio-legend Paul Klipsch wore a button under his lapel that said Bullsxxt. He would flash it to someone who would engage with him on some audio-related topic (when appropriate of course).
I'm not at all an engineer, but like to read and learn to educate myself the gear I use and how they work (Roger's product manuals are great that way).
Over the years, I've come across various statements frequently made on discussion boards regarding amplifier design. As with all things, there is a bit of truth and some B.S. with each in the list below. These are NOT my ideas. Curious as to what others think ...
1. Transformers: The bigger “iron”, the better, hence massive power supplies and output transfers sound best.
2. Rectification: Tube rectification is better than diode, preferably with a choke in PS
3. Tubes: NOS is generally better than today's Chinese, Russian, Czech and former Yugo production. It's more than just testing well.
4. Parts I - Caps : Good ol’ Sprague caps sound better than new expensive exotics
5. Parts II - Materials: Silver is better if you can afford it. Silver transformers, wiring, etc…
6. Design: Fewer stages the better
7. Negative Feedback: Preferably none. Zero NFB is best
8. Design II: Class A … nuff said, generally sounds better than AB, B and other variants
9. Construction: Hand wired is generally better than PCB
10. Straight wire with gain : Tone controls are generally bad, another complexity to degrade the signal from "purity"
11. Transformer II: Transformer-coupled amps perform better than those using a cap between stages
12. Made in the USA: The Chinese don't care about quality of products. Made in the USA is best if you want your amp to last.
I would say with all of these, its a matter of implementation, thus "generalized" statements are mostly untrue. However, what is the "real story" with these? They can't be entirely right or wrong either.