A question I suspect reveals a lot of ignorance...

I believe that when a tube amp is at idle, it draws full rated power/current. Increasing volume doesn't draw more than its rated power...however, it can drive the amp to clipping, which can be detrimental to the life of the tubes..especially tubes that are worn down, and don't hold their bias.

Beavis
Question.How do you know you are at 85db when listening?Do you use a meter?If so why?I suspect for safe hearing levels but I like to hear your reasons!
Regards
George

Kehut

The amp would only draw full rated current from the power supply if operates in Class A. All single ended amps are class A but few others are. Most operate in Class AB and draw much less current at idle than when driven.

I know from experience that power tubes in guitar amps have shorter life when routinely driven hard. I think the same will be true for high fi tube power amps, though the conditions in most hi fi amps are much less severe than in the average guitar amp.

Thanks all.
Kehut - yes, I agree on the dangers posed by over-driving and clipping. That hasn't been an issue so far even though I'm driving Totem Forests (not very efficient) with a Jolida 502B. Good news there from what I've read is that the Forest's impedance curve doesn't drop all that low. (as a side note the only CD where I thought I was starting to get some distortion is the Stones, "A Bigger Bang"...that is a loud recording and I usually have to back off the volume on that compared to some older CDs.)

My practice too is to turn on the amp 30-60 min before I sit down to listen. Sometimes I'll play a CD on repeat while off doing other things. Seems like the amp warm up result is different after a period of simply being on vs having "worked" during that time. FWIW I also unplug my equipment when not in use.

I don't know what class of amp my Jolida 502B is or what the various classes mean...I can certainly research that but if anyone feels inclined to summarize - that would be appreciated.

I'm not sure there's a concensus here about the original question. Intuitively, it seems like playing louder would work the tubes harder but I'm not a an electronics engineer. I suspect its true as several have noted, differences in hi-fi/home listening volume levels won't have a significant impact on tube life.

Thanks again.

I'm not posting this to start an argument. I equate this from a mechanical view.Consider the life of a gas powered motor vs. a diesel motor.Higher rpm's equals shorter life span.Simple idea.
A good question. If we could get someone that absolutely knows the answer,it would be great.