Kevziek: Most of Nelson Pass' amps are of a high bias design and run hot. Leaving them on exposes the caps to a greater amount of heat, so they will end up "cooking" themselves and drying out. Then again, if one turns the amp off and on as needed, the caps are exposed to big temperature swings from the amp being stone cold and then coming up to operating temperature. Doing this repeatedly stresses the caps more than leaving them turned on all the time. That is, so long as the amp has proper ventilation both internally and externally to begin with.
This is not to mention that leaving them on reduces the amount of exposure to high levels of in-rush current. It is in-rush current that damages equipment the most due to the huge surges involved and the rapid internal temperature changes that take place when this occurs. This is why light bulbs typically blow when turning them on, not once they are already on.
Other than that, Seandtaylor did a nice job. GS's comments are right in the ball park too, but one has to realize that not all caps are made the same or have the same spec's and reliability. For that matter, caps from the same manufacturer and of the same product line may differ due to variances in the dielectrics used from batch to batch. Some batch's of products are much better / reliable than others.
As a side note, just a while back i pulled some caps from an amp that Nelson designed and released in appr 1990. While this amp is 13 years old and idles at about 130* at the heatsink, it has been on 24/7 for over three years. With all of that in mind, the electrolytics in the power supply actually tested above their rated values by almost 20%. Needless to say, i didn't replace them as there was no need. Sean
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