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Capacitors drying out in an old amp

If one is evaluating old amplifiers how does one know if the capacitors are drying out/dried out. Does the drying out process take a long time? Say, 1 or 2 years or is it quick?

Can the ears tell us if it is so?

I tried to check this but could not come up with anything. However most agree that an amp which is over 15 years old most probably needs the capacitors to be changed.

Quad amps have the current dumping system and according to what I have read are sort of self adjusting amps which do not change the sound characteristics over certain period of time. Is this also related to the issue raised above.

Sorry for so many questions but if someone can explain in laymans terms if possible, it would be greatly appreciated.

Thanks
128x128quadophile

Showing 3 responses by herman

herman
2,215 posts
 
Hpims, thanks for colaborating my point with your experience with the 240.

Electrolytics deteriorate and must be replaced periodicaly. If the 225 starts to hum tomorrow do you think it was perfect today. NO, the sound degrades slowly and at some point the cap will deteriorate to the point that you can hear some hum, but the sound has been degrading long before you hear a hum.
herman
2,215 posts
 
The only ones that deteriorate are the electrolytics.

Check out this discussion of aging capacitors. If it were mine I would change them. It is cheap and easy if you can solder.

The current dumping topology is another matter.
herman
2,215 posts
 
It has little to do with the build quality. A 40 year old electrolytic capacitor is not behaving the same as a new one. A 40 year old amp may be functioning with no apparent problems, but it is not functioning as well as it was when it was new.
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