Class D, really? I suppose in the modern unsustainable consumer disposable society they may be relevant and sound ok. The question I pose is, will they be durable and serviceable in 20+ years or just another contribution to electronic waste ? I say this listening to a 30 + year old jfet cascode afe and mosfet ops Hafler 9500. This amp was restored to perfection by myself with all the best components (Audio Note, Mundorf, Dale , Exicon, Cardas, Sparko Labs front end power supply, etc..). Still believe super fast switching will never beat no switching. And tend to believe too much switching is detrimental to ones health. it could possibly be why analog audio is so meditative for me.... Ok thanks for reading my rant about class D. To be honest l, just don’t understand class D schematics and topology. I do understand that most here are not builders, but please to those who are not, consider that your choice will limit the supply of anything worth keeping out of the landfill in the future..
@pwayland If care isn’t taken, all sorts of things wind up in the waste stream. 35 years ago I pulled a set of vacuum-tube Western Electric microphone preamps out of a dumpster. We still use them (refurbished) in our recording studio. So I share that concern! It is for that concern that we have offered warranty reactivation on any of our older products should it be updated or renovated.
The semiconductor industry seems as if it prefers to make switching devices rather than linear devices. So the likelihood is good that in 30 years an older class D amp could be refurbished and put back on the road. Other than the class D module all class D amps have a power supply and chassis like a conventional amplifier. So at worst you would be replacing the module.
Class D as a class of operation proposed in the 1950s when tubes were King. You could make a vacuum tube class D amp if you wanted. The first home units were made in the 1960s and more were made in the 1970s and 80s, some by Sony and Yamaha (many of which are still running, so you have your answer since they are already over 30 years old...)
FWIW there is no health risk whatsoever from a class D module that meets European Directives for radiation. No-one in their right mind would sell a module that didn’t!! IOW they don’t radiate RF energy or the like that could be construed in any way to be a health hazard.
Class D is as durable as any other amplifier tech. I’ve been using a Crown class D amp in my keyboard rig in my band for over ten years. It gets quite a bit of abuse and keeps working fine. IMO/IME a conventional solid state AB amp is at greater risk due to oscillation concerns with certain loads, heat issues and the like. So, like a conventional AB amplifier, as long as the circuit has some protections in place it will be pretty goof-proof.
Its the distortion spectra and how much distortion that determines how the amp will sound. The class of operation does not. It is this very reason why class D can sound as good as the best class A or tube (possibly also class A) amplifiers, since with those amps the ’sonic signature’ is in fact the ’distortion signature’. Whether a designer of an amp understands this fact is a very different topic!
