Capacitors wear out with time. Like it or not, it’s a fact of life.

All audio gear has plenty of capacitors in them.

Replacing is a mandatory step in preserving your gear and having it perform as per the original specs. (of better if you use TOTL parts)

 

Running a 15+ years old amplifier without a recap, is like running a 15 year old sport car on its original tires, as rubber deteriorates and cracks with time, rendering tires and the car unsafe.

 

Refreshing capacitors in audio gear brings them back to life.

• Bass authority is restored. We often forget the "slam" an amplifier used to provide.

• Treble definition returns.

• Mid-range pureness is possible once again.

• The power amplifier usually benefits the most, as they normally generate more internal heat. Heat accelerate the capacitor wear.

 

Today’s parts are much better than parts manufactured just 10 years ago. Performance increases in both electrical specs and reliability and they are often much smaller as well. For a given circuit board room, one can use bigger values and stay within physical size allowed.

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Some capacitors now have a useful life of 10,000 hours at 105ºC, such as the Panasonic FR series for example. This is a big contrast from typical OEM parts in 10 year old audio gear rated at 1,000 or 2,000 hours at 85ºC.

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If your gear is 15 years old or more, I always recommend at least a partial "recap".

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Excerpt from Wikipedia: https://en.wikipedia.org/wiki/Electrolytic_capacitor

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“The lifetime, service life, load life or useful life of electrolytic capacitors is a special characteristic of non-solid aluminum electrolytic capacitors, whose liquid electrolyte can evaporate over time. Lowering the electrolyte level influences the electrical parameters of the capacitors. The capacitance decreases and the impedance and ESR increase with decreasing amounts of electrolyte. This very slow electrolyte drying-out depends on the temperature, the applied ripple current load, and the applied voltage. The lower these parameters compared with their maximum values the longer the capacitor's “life”. The “end of life” point is defined by the appearance of wear-out failures or degradation failures when either capacitance, impedance, ESR or leakage current exceed their specified change limits.

The lifetime is a specification of a collection of tested capacitors and delivers an expectation of the behavior of similar types. This lifetime definition corresponds with the time of the constant random failure rate in the bathtub curve.

But even after exceeding the specified limits and the capacitors having reached their “end of life” the electronic circuit is not in immediate danger; only the functionality of the capacitors is reduced. With today's high levels of purity in the manufacture of electrolytic capacitors it is not to be expected that short circuits occur after the end-of-life-point with progressive evaporation combined with parameter degradation.

The lifetime of non-solid aluminum electrolytic capacitors is specified in terms of “hours per temperature", like "2,000h/105°C". With this specification the lifetime at operational conditions can be estimated by special formulas or graphs specified in the data sheets of serious manufacturers. They use different ways for specification, some give special formulas, others specify their e-caps lifetime calculation with graphs that consider the influence of applied voltage. Basic principle for calculating the time under operational conditions is the so-called “10-degree-rule”.

This rule is also known as Arrhenius rule. It characterizes the change of thermic reaction speed. For every 10°C lower temperature the evaporation is reduced by half. That means for every 10°C lower temperature the lifetime of capacitors doubles. If a lifetime specification of an electrolytic capacitor is, for example, 2000  h/105°C, the capacitor's lifetime at 45°C can be ”calculated” as 128,000 hours—that is roughly 15 years—by using the 10-degrees-rule.

However, solid polymer electrolytic capacitors, aluminum as well as tantalum and niobium electrolytic capacitors also have a lifetime specification. The polymer electrolyte has a small deterioration of conductivity caused by a thermal degradation mechanism in the conductive polymer. The electrical conductivity decreases as a function of time, in agreement with a granular metal type structure, in which aging is due to the shrinking of the conductive polymer grains. The lifetime of polymer electrolytic capacitors is specified in terms similar to non-solid e-caps but its lifetime calculation follows other rules, leading to much longer operational lifetimes.

Tantalum electrolytic capacitors with solid manganese dioxide electrolyte do not have wear-out failures so they do not have a lifetime specification in the sense of non-solid aluminum electrolytic capacitors. Also, tantalum capacitors with non-solid electrolyte, the "wet tantalums", do not have a lifetime specification because they are hermetically sealed and evaporation of electrolyte is minimized.

Electrolytic capacitors with solid electrolyte do not have wear-out failures so they do not have a lifetime specification in the sense of non-solid aluminum electrolytic capacitors.”