SirSpeedy:
Does turning equipment on and off damage it? Over time, yes, some equipment more than others depending upon how hot equipment gets, as the hotter a piece gets when powered up, the more expansion and contraction occurs when it is turned off and cools down (it is expansion and contraction that causes components to fail over time). Leaving equipment on 24/7 does subject the caps to additional wear, as a cap is smacked around by alternating current waveforms (hence the term "A/C") whenever power flows to it, but good caps last many years even when seeing power 24/7 and are easy and relatively cheap to replace. The other parts of a component are not necessarily easy or cheap to replace, however, and the best way to protect them is to keep them at a constant temperature. People think that solid-state amps are easier to own and more "reliable" than tube amps -- wrong -- ask Krell and Madrigal amp owners that question after they lose transistors and then discover that the transistor is no longer made. In this regard, the riskiest component to buy used is probably a solid-state power amp -- most people turn them on and off, and after a number of years of being "pulled in and out of the fire", so to speak, some internal components have literally become brittle (a tube amp, on the other hand, essentially becomes a "new" component when it is retubed). Ask any honest tech who works on these things (the dishonest ones will say "turn it off", as it helps keep them busy). Manufacturers will tell you the same off the record, but often say "turn it off" in owners manuals because of liability concerns. Others want you to have best sound and most reliability, and do not include an on/off switch at all -- when the component is plugged in, it's on. Some components have to be turned off or can be more safely turned off. For example, tube amps must be turned off because output tubes pass a lot of current and last longer if powered down when not in use. Class A-biased solid-state amps burn a ton of electricity and heat up a room when left on constantly, as well as go out of bias too quickly. A component using small-signal tubes (preamps, DAC's, etc.) can be turned on and off if it also uses tube rectification, as the tubes in the power supply bring voltage up to the other tubes very gently, but most tube gear uses solid-state rectification, which is the biggest reason why people are constantly, and unnecessarily, replacing small-signal tubes (at power-up, the voltage applied to the tubes is like a kick to the groin).
All of that said, if you feel that you have to unplug your equipment to protect it against electrical storms, then you have to unplug your equipment -- suddenly running a few hundred thousand volts through your equipment is an extreme example of the deleterious effects of thermal cycles.
Does turning equipment on and off damage it? Over time, yes, some equipment more than others depending upon how hot equipment gets, as the hotter a piece gets when powered up, the more expansion and contraction occurs when it is turned off and cools down (it is expansion and contraction that causes components to fail over time). Leaving equipment on 24/7 does subject the caps to additional wear, as a cap is smacked around by alternating current waveforms (hence the term "A/C") whenever power flows to it, but good caps last many years even when seeing power 24/7 and are easy and relatively cheap to replace. The other parts of a component are not necessarily easy or cheap to replace, however, and the best way to protect them is to keep them at a constant temperature. People think that solid-state amps are easier to own and more "reliable" than tube amps -- wrong -- ask Krell and Madrigal amp owners that question after they lose transistors and then discover that the transistor is no longer made. In this regard, the riskiest component to buy used is probably a solid-state power amp -- most people turn them on and off, and after a number of years of being "pulled in and out of the fire", so to speak, some internal components have literally become brittle (a tube amp, on the other hand, essentially becomes a "new" component when it is retubed). Ask any honest tech who works on these things (the dishonest ones will say "turn it off", as it helps keep them busy). Manufacturers will tell you the same off the record, but often say "turn it off" in owners manuals because of liability concerns. Others want you to have best sound and most reliability, and do not include an on/off switch at all -- when the component is plugged in, it's on. Some components have to be turned off or can be more safely turned off. For example, tube amps must be turned off because output tubes pass a lot of current and last longer if powered down when not in use. Class A-biased solid-state amps burn a ton of electricity and heat up a room when left on constantly, as well as go out of bias too quickly. A component using small-signal tubes (preamps, DAC's, etc.) can be turned on and off if it also uses tube rectification, as the tubes in the power supply bring voltage up to the other tubes very gently, but most tube gear uses solid-state rectification, which is the biggest reason why people are constantly, and unnecessarily, replacing small-signal tubes (at power-up, the voltage applied to the tubes is like a kick to the groin).
All of that said, if you feel that you have to unplug your equipment to protect it against electrical storms, then you have to unplug your equipment -- suddenly running a few hundred thousand volts through your equipment is an extreme example of the deleterious effects of thermal cycles.