Quick question about filtercaps

[Oddvar R]

I have some electrolytic capacitors that differ in size, but have the same value. Does size matter?

[martin manning]

As long as the voltage ratings are adequate they should be ok to use. The size difference can be due to manufacturing technology, voltage rating, temperature rating, or service life, where increases in any of those parameters generally produces a larger part.

[Oddvar R]

Thanks...

[Stevem]

In a tube amp size does not matter ( as long as you have the real estate) as much as the caps temperature rating.

Filters rated at 85 degrees C will live a shorter life and start to go down hill much faster then the superior ones rated at 105 C.

[Oddvar R]

In a tube amp size does not matter ( as long as you have the real estate) as much as the caps temperature rating.

Filters rated at 85 degrees C will live a shorter life and start to go down hill much faster then the superior ones rated at 105 C.

Tha is an interesting question, because often the tempreture ratings isn't stated in layouts. When I made the Soldano Slo 100 w from Rob Reeder at C3 amps he said this about the caps:
"The cap temperature refers the quality and longevity of the caps. The 105 degree caps are milspec and have a higher hour rating. Either will work fine in the amp."

I wonder what "higher hour rating" means. Is there two hour difference or 200 hours?

[pdf64]

Electrolytic caps have a rated operational life, x hours @ y volts @ z°C. Have a look at the info at Mouser etc.
My impression is that cap life increases at least linearly, perhaps near exponentially, as the voltage or temperature is reduced from the rated level.
So 5k hours at 105C and 500V would be at least 10k hours, probably far more, at 50C and 500V.

[gktamps]

You can find life x temp ratings for most caps in the datasheets for the particular series.