Stress on Solid State Amps

IMHO its just "owned by a LOL" stuff; and probably just BS. I've been seeing a lot of that lately in the ads. Nothing is used more than 200 hours and all gently - oh yeh! Caveat emptor as always.

Yeah no kidding buddy.
And they "never play anything but the highest calubur of music on it" either

Honestly, if an amplifier cant handle something hard and heavy, like KMFDM, then why would anyone buy it? Its not that you HAVE to play that on it, but it SHOULD be able to handle it without having any problems.
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Oh, Look at Hoity Toity Me! I have a $100,000 stereo system that is so refined and delicate that Metallica would turn it into a big melted bubbly mass of plastic silicon and metal!

I call my stereo FiFi, and only allow the finest calibur of people to be in its presence! In fact, the system has been so sheltered and babied, that no crude beer guzzling heathens have ever beheld its presence and corrupted its pure nature!
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Give me a break. As if playing some rock on it will damage it. If it DOES damage it, i wouldnt let my dog fart on it to cool it down.

My take on your use of the word "dependable" is the synonym "reliable" as in probability of failure. In this case yes, an amp that has been pushed hard will be less reliable. Fuses might be more likely to blow if they've experienced repeated heating to near their "blow" point. The output transistors might likewise have experienced some aging from approaching their thermal limits. The power transformer will likewise have experienced some aging from high temperature operation. The power supply capacitors might have aged some from a history of high current.

Though the answer is yes, an amp that has been run hard will be less reliable (more prone to failure), I would not expect a large difference in reliability between it and a "lightly" used amp. Well made amps just don't fail all that often. A heavily used amp might survive many years. On the other hand a lightly used amp can fail from any of many possible "factory defects" that remain latent until exposed by use.

All else being equal, and having a choice, the amp with a "light use" history would be the better choice and worth a few bucks more.

As for the seller's honesty or judgment as to what's hard usage and what's light usage, the best bet is always to know the seller. Give him a call and get a feel for his situation (how he's used the amp). Also be sure he's the only previous owner (he likely can't vouch for the previous owner(s)).

If the amp was never stressed then you are stuck waiting for it to break/burn in. Unless you are planning to camp out in an igloo and subject it to dramatic temperature swings it is difficult to over stress it under normal household conditions.

Creating power requires heat dissipation and modern electronics are designed with high temperatures in mind. Dependable is a manufacturer trait and unless someone has totally swamped the amp with high loads or bridged it to beyond specification normal use shouldn't affect its life span.

In fact, the Wadia 27 DAC runs so hot, as it was designed, one can make breakfast on it.

I also have for sale a 69 Hemi Charger that my grandmother only drove to church on Sundays and has never been stressed.

An amp is "stressed" much more by turning it on from a cold start than by playing it full volume for weeks on end. An amp driven to clipping occasionally or if played at higher power settings is more dependable than an amp that has been sitting idle for years - but not less dependable than one that's been coddled. Things like humidity, temperature extremes, cigarette smoke, pet dander, electrical surges and the like will have a far greater impact on life expectancy than just by simply playing it loud or often. No one will mention those stress items in their ads too frequently...