Can the sound of SS amp deteriorate over time??

Short of bench testing an amp to determine if it meets spec, there is no way to tell for sure. Many, who consider measurements verboten, foolishly waste time & $ with ZERO improvement.

I've left my modified Adcom on for 15+ years and I've heard no deteriation in the sound.As someone said the design and how well you take care of your equipment comes into play. I also feel that providing your SS equipment with purified electricity provided by a good AC line conditioner and good power chords can't hurt.

Porziob: Thanks for clearing that up for me. I, my annnually calibrated test equipment ( HP spectrum analyzer, tracking generator, AF & RF signal generators, Tek scopes, etc... )and the experiences of the mass majority of my customers must all be mistaken. I guess that i'll have to start denying the differences that the customers experience and what i can measure, based on your above testimony.

Qdrone: It is my personal belief that leaving equipment on causes less stress than power cycling it up and down on a regular basis. That is, so long as their is more than adequate ventilation for such and "dust bunnies" that can accumulate both on and in the gear are addressed on a somewhat regular basis. Not only that, but i think that most gear sounds better too. Obviously, this is just my personal opinion, so take it for what it is worth. Sean
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Sean...In the field of ballistic missile guidance systems (lots of very complex and precise solid state electronics) we have rather extensive experience with continuous operation and with on/off operation. (The Air Force operates continuously while the Navy operates on/off). Navy systems are commonly deployed without problems for six to ten years, whereas Air Force systems last a much shorter time (which I can't tell). Believe me, the Navy has also looked very closely at possible accuracy benefits of continuous operation, and it is not significant. However, it is important that the Navy systems opearate in a "Dormant" mode when "off", where heaters distributed throughout the system maintain temperatures very close to those that exist during operation.

Yes it can, for a varity of reasons. The main resevoir caps(the large cans) in most high end amps are charged thru a very low series resistance. The current surge upon turn on present a "shock" to the cap, and over time causes excessive DC leakage. This can easily be measured, however after 10 yrs of, say daily cycling, it becomes prudent to replace them in order to avoid the possibility of the cap shorting. Many quality amp provide a means to adjust output transistor idle bias and DC offset. This needs to be periodicly checked and/or adjusted. Semiconductor chactoristics change over time and temperature cycling. I can provide assistance in most cases, if you are interested.