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Capacitors: Who is Right? What ages them faster?

Power supply electrolytics - the main thing audiophiles worry about getting old and having to replace.

What's the truth here?

Manufacturers can be quoted as saying the life expectancy of caps is anywhere from 10 - 15 years. Is this true? Why is it that Krell amps seem to need capacitor changes in 8 years, while people have receivers from the 70's that never had caps replaced?

Another controversy, with three viewpoints:

(1) I was told that caps age faster in amps that are left on continuously. The rationale here is that the lack of a discharge cycle is not good for the caps since they are in a constantly charged state.

(2) Others claim that leaving a unit unused in a box for years also shortens the life of the caps, as they never see a charge.

(3) Others say the lifespan is the same whether on the shelf, or in the unit.

Who has the technical background or the knowledge to sort this out?
kevziek
seandtaylor99
1,262 posts
 
My educated guess is that none of 1, 2, or 3 are correct, and that what really causes cap aging is thermal cycling. Krells tend to run hot (never owned one, but they have huge heatsinks for a reason), so this might shorten the life.

Leaving equipment off for a long period is probably OK, leaving it on for a long period is probably OK, but switching on and off every day is probably not so good due to the thermal cycling, which causes mechanical stresses (expansion and contraction).

The lifetime will also vary with the quality of the parts.

So if I were you I'd leave all solid state stuff on all the time to minimize temperature variations and condensation problems.

Another thing to bear in mind is that some manufacturers and repair houses make a lot of money swapping caps, and so it pays them to put fear into the audio community that their caps are bad and need changing. By analogy, try to find a car mechanic who'll tell you that oil really doesn't need to be changed every 3000 miles.
gs5556
1,239 posts
 
I have seen data sheets that give operational life as much as 300,000 hours (34 years), with a shelf life as high as 10 to 15 years "...without deterioration of quality". What will affect the life span is the ambient temperature (if too high, the caps will start leaking current), the ripple current frequency and the initial temperature rise (on/off operation). If you leave the amps off, then you increase the life span by virture of zero frequency but lose it when you turn on the amps (high initial temp rise). If you leave the amps on, then the reverse is true - so, to me, it's a wash whether you keep the amp on or off.

But 8 years to a ps filter cap? Doesn't sound right to me, nor have I heard that Krell caps have such a problem; however 34 plus years for a cap is, IMO, a bit on the optimistic side. I would guess that 15 to 20 yrs would be in the ballpark. Then again, my ML 20.6 pc boards were replaced twice in 15 years. Because of bad caps.
unsound
7,333 posts
 
What does this mean with regard to those amps that use few large value caps as opposed to those amps that use more smaller value caps?
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