While repairs for surface mount components happen in other fields the cost of them turns an amp into a disposable item. 5 years from now will there be the correct class D module that will fit and match other other channel? Let alone 50 years like tubes.
Replacing an entire 'module' requires treating an entire part of an amp as just a single component. It really embraces the 'throw it away and ship another one half way around the world' reality that we all know now. But enjoy the 'efficiency' of the cheap amp....
Do SS AB amps typically need components replaced rather than just checked and adjust the bias?
Based on Restorer-John's earlier comment I'm half tempted to put a tiny schematic and biasing instructions in my amps, along with spare transistors with the hope that maybe someday someone would give them more decades of life.
OK. So what’s the most expensive part to replace I an amp: any Hypex module, or the genuine WE 300B tube?
Which of the two is most likely to be repairable? Which is most likely to be recyclable?
Which has the longest MTBF?
Which amp containing one of the two is most likely to have a different sound after replacement?
How does those questions work against any class A amp of equivalent or even lower power? It’s not like components used in class AB amps have never gone out of production, or been replaced with lower quality equivalents.
And can you name any.class D module that has gone out of production in ten years after introduction? Twenty? Come on. Some chip amps, maybe, but how many of them don't have equivalents, either?
The answers to some of these questions obviously can change over time. That class D module with surface mount components is obviously only viable for repair by a trained person with surface mount equipment, and that may not be the average hifi repairer today. Most surface mount equipment has a shorter life because it is technology like TVs and computers that are replaced as outdated equipment often before they fail, so there's a question of viability of a business doing those kinds of repairs. If in five years' time more stuff is worth having surface mount repairs done to them, why should we not see more qualified repairers and businesses? Car maintenance has changed massively in recent years, but the industry changed to match, didn't it?
But to say that one technology is more reliable than the other, as a general case, I'd say is wrong. Looking at the question today from a historical viewpoint (my fifty year old amp is fine) puts blinkers on the requirements and infrastructure needed for an amp bought today to be reliable or worth keeping into the future. That module may be fully recyclable and still cheaper than maintaining a high power class AB amp built today, with today's components. What we need maybe are the
standards of fifty years ago, not necessarily the same products.
A point relevant here is self repair of products, which will demand module replacement as the repair. I do see this as a problem for people used to maintaining their own equipment, which is part of the hobby here after all.
Finally, my point of view here may be different to others because my amp is a Marantz PM-10, where the modules are part of the amp, but hardly the percentage of the product that a reference build based Hypex or Purify power amp would be.