It feels good to see a designer/engineer wrote articles on design guidelines while brave enough to debunk some myths at the same time; and I am happy to know I wasn't the only one saying things like:
"
Measurements are not meaningless, and real world signals are sinewaves! The only difference is that with music, there is usually a large number of sinewaves, all added together. There is not a myriad of simultaneous signals passing through an amp, just one (for a single channel, naturally)."
"
We need measurements, because they tell us about the things that we often either can't hear, or that may be audible in a way that confuses our senses. Listening tests are also necessary, but they must be properly conducted as a true blind A-B test or the results are meaningless. Sighted tests (where you know exactly which piece of gear you are listening to) are fatally flawed and will almost always provide the expected outcome."
His linked article on power supplies is also a good read, it should answer some of the questions
@RickyT raised recently on transformer size. Highly recommended for "DIYists".. It explains in easy to understand language, why manufacturers are able to go with PS transformers much smaller than what appears to be another apparently popular that it has to be sized to account for the class AB efficiency of between 50-75% (approx.).
ESP - The Audio Pages. Linear power supply design information - Learn how to design your own high performance amplifier power supply.
sound-au.com
Commercial designs
always have a series of compromises and trade-offs, while a DIY design does not have to play by the same artificial rules to make a $.
There are a few authors for amp design that have several books that should be read and understood by any audio electronics engineer or designer (commercial or DIY).
Douglas Self
The Signal Transfer Company, audio, preamp, power amps
www.signaltransfer.freeuk.com
G Randy Slone
https://www.amazon.com/gp/product/0071341196/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1
Bob Cordell
https://www.amazon.com/gp/product/007164024X/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1
If you read and understand their work, and apply their principles taught, you WILL be a world class amplifier designer! Of course, no snake oil here, other than debunking their rubbish!
I started my amplifier design journey at the Power Supply. I have designed, sourced parts, and built a few Power Supplies for DIY amps and other audio gear. So, I have a thorough understanding of what is needed, and what is not needed or detrimental for an amplifier power supply.
Spoiler Alert: for a power amp, the ideal PS is a robust non-regulated linear power supply, while a SMPS is the worst choice. The caveat is that there have been advances in SMPS, but the parts count, and inherent problems that require workarounds for audio applications make SMPS remain a less ideal option (if pure performance
measurements and reliability are the dominate design goals).