I have a couple of hifi amp units that I haven’t used for a few years and consequently thinking of moving them on. I really can’t be expected to remember how they sounded when last used and wondered if capacitors degrade over time when power isn’t applied to them or the degradation only happens in use. I suppose it depends on what time of capacitor they are I suppose. What’s the answer. If I need to re-cap them what makes a particular manufacturers capacitor better than somebody elses given the same values?
To answer your titular question briefly; yes!
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All electrolytic capacitors will degrade even when not powered. The liquid in them can begin to dry, making them less effective.
However, long term use, in my view, will do more to degrade the capacitors than being stuck on a shelf unpowered. It is also true that many capacitors will measure within spec after decades have passed.
If you paid someone to recap a unit you are unlikely to recoup the cost of paying for that service when you sell it. In the case of kit from Naim it will help get a better price due to most Naim customers know that recapping is a good thing periodically.
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Generally speaking, I believe the answer is “None to very little.” Indeed, that seems to fit with my own experience. I recently took an amp out of storage that had not been powered up for about 5 years. Sounded excellent. It also depends to some extent on how the amp was stored. If it was kept in a damp and dusty environment where grime and moisture can build up inside, (or very hot or very cold) then it may require some work or not work at all. Perhaps a bigger problem might be the switches, volume pot, relays, etc. If you are thinking of selling, then why not power it up, see if everything is working and then sell accompanied by an honest description?
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@Loki. I know they do but when unpowered? @Robinho says they do but much more slowly. The units I’m thinking of moving on are Musical Fidelity 3.2 pre and power amps. They were the British made one’s before they shipped out their manufacturing to Taiwan. However, I believe they didn’t use the best capacitors available when they were British made. I’m thinking maybe I should give them a listen as is and then re-cap them myself if they sound a bit flat. A visual inspection is one thing but, unless they’re showing obvious signs of bulging, it won’t tell my if they’re shot or passed their best. What characteristics in terms of PRaT will they exhibit if they’re buggered? My soldering skills are good so I’m happy to replace them myself but don’t want to do that if they’re OK. There are different types of capacitor of course and then there are specific specialist audio ones but I’ve really no idea what makes one better than another. There’s a big difference in cost. What are you paying the premium for?
From the Naim website:
- Equipment servicing (certain components, predominantly capacitors, degrade with age and require replacement periodically to sustain optimal performance)
Yes that’s true but given that the advice also is to leave equipment powered they will indeed degrade faster than capacitors just sat on a shelf.
If I was the OP I would test the equipment for function and as mentioned above sell with an honest description.
They won’t, the degradation is due to a chemical reaction unrelated to electrons passing through.
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It would take a long time to explain.
If it works and sounds OK, I’d sell it as unserviced. If it needs recapping, I’d buy a kit.
It’s not as simple as just selecting a type of capacitor. They don’t sound the same. They are used for different applications. EG. Feedback, coupling, decoupling…
I’d always do that. When I last used them a few years ago they certainly delivered. Presentation and soundstage was all there. Definitely not Naim amps but great in their own way and probably more suited to rock than classical. I’ve been down the Naim route a long while now and overall the sound suits me but I’d never knock those amps. Probably why I’ve kept hold of them. If I had a home with several music rooms it would be ideal for comparison purposes but hey ho. 2 systems is all I have. One in the lounge and one in the office, both Naim but the latter being a more modest Naim system.
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I disagree but as well as being powered the warmth generated by being on does effect the capacitors and will degrade them faster. The charging and discharging cycles effect the chemicals in the capacitor. I have some very old unused capacitors that measure within spec. I don’t expect they would sound great or last a long time if fitted but they measure OK.
Some can sit in the drawer and go bad too but that is potentially manufacturing issues.
My recollection on when this has been discussed before, is that the biggest factor is just age, then the next factor is being powered on then off again, hence why Naim users tend to leave them on most of the time. The usual response to this is , “so what’s all this standby business then”, and the answer to that is simply the requirement to meet the latest power rules and regulation which force Naim down the route to offering this, but there is still often the option to leave on if wanted.
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Most electrolytic capacitors have a defined operating lifetime stated on their specsheet including the period within which they should be used in manufacturing after their initial production. That shelf life alone is usually quoted as 18 months to 2 years. After that period, they will still function and measure within spec but their remaining service life may not be sufficient for the warranty requirement of the product they are going into.
Polymer caps will last substantially longer but not forever, and ceramic caps longer still. But ultimately everything degrades with time.
As they behave differently they are generally not that interchangeable except at the boundary areas where type of cap’s functional limits end and another’s begin there is crossover allowing for selection of either.
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What caps used in 500 series? @feeling_zen
David
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Certainly electrolytic capacitors can degrade when not in use. One risk with powering up something that has been dormant for a long time is the potential for a dried out capacitor to explode. However I think the time period is many years, perhaps decades, and IIRC primarily a risk with high voltage circuits such as valve (tube) amps. My understanding is that the main difference between being in use and out of use is heat, particularly in power amps and power suppliers which can get hot, the heat accelerating degradation, the hotter the greater likely rate, especially idf run above their rated maximum working temperature. That said, some years ago when I sent a MF P270 for service at about 25 years of age, they didn’t replace the reservoir capacitors because they tested within spec - and that is despite the amp casing around them getting up to around 60 C when playing spiritedly, which was not uncommon with my use.
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That’s probably a question for Naim but they won’t invite any user self-servicing.
But it’s also a bit vague. The 500 system comprises of various products which use a wide variety of capacitors of different types in different places from different vendors. They will almost certainly use all three constructions from ceramic, polymer and electrolyte in hundreds of different places across a 552, 500, 500PS, 555, 555PS, 552PS.
And if I was Naim, my first response would be with a question, “why do you want to know?" What problem are you attempting to solve?”
Curiosity
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Usually the capacitor list for a PCB is very long. I don’t see them providing that. They might mention the large caps on the power supplies but for everything else, you will need a mirror and a loupe.
Note that for the hundreds of surface mount ceramic caps on a PCB like in the ND555 they are likely the very small ones with zero text on them. You’d just have to know or take them out and measure. The chances of doing so without breaking the unit being nearly 0% for most people.
The big caps you can just see for yourself after removing the case.
It’s interesting that you pulled that up from AI because I was looking at the same stuff which lead me to the OP. I also have a Musical Fidelity Tri-Vista 21 DAC that I’ve had for several years. It was when looking at Maudifi’s videos on you tube I was wondering if I should re-cap it. From memory I bought it used for about £800. Maudifi sell kits to re-cap and modify it at various stage of upgrade. The bill of materials for the stage 3 upgrade would cost more the DAC cost me initially. It also mentions the Rock Grotto upgrade for the X-Can. Mine packed in and I replaced the valves and recapped it myself for a lot less than their kit (which didn’t include the tubes) and I still have it in use. It must be 20 years old now and probably worth another recap but can’t say I’ve noticed degradation in sound quality. In fact I prefer it over my Headline. Seems like there is a very lucrative business in servicing hifi equipment that may or may not be purely nugatory.
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I’ve a Rega io which has been used for a month and from now will be used only as a back up to my valve amp. I’ve boxed it back up and it’s stored under the desk in our home office/study. Room is a fairly consistent temperature. I am assuming that’s fine and the biggest factor will simply be age?