How long electrolytic caps last?

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I have just removed some electrolytics from my preamp with a thought that I might use them in my SOZ. After I checked them I was quite dissapointed. They measure nothing and don't get charged when I connect them to PS. They've been in a preamp for 7 years and the power was always on. Four caps in parallel, 3,000uF/40V ea. Is that normal? I've heard about caps aging but never observed it first hand. BTW I still have the same caps which I never used and they measure perfectly. The ones that are more yellow are the defective ones.
Thanks for your advice.


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There are many factors

1. Technology: Dry electrolytics last "forever"
2. Wet ones: Depends on a) physical size (takes longer to evaporate), temperature exposed to, core temperature, construction of seals.
3. Overloading/loading -- voltage and current.

Caps that are smaller than .75" diameter should not be trusted for more than 10 years unless particularly high quality or if kept at low voltages, or better still low currents.

If they have not been used for a while, you might want to charge them up 10 120% of rating through a resistor so that current is kept low + leave with voltage on for 10-15 minutes. You could use say 100-1000 Ohms, it is not critical, but you probably need a high power unit.

Electrolytic life is highly dependant on how you use them. The big killer is heat. Heat can come from both external sources and internal sources. If you put those in a power amp that runs hot, that could be an issue. In a low temp pre-amp, that should not be so much of an issue. Internal heating is of course from losses in the cap from in-circuit use. One thing to watch is that you are not exceeding the ripple current. That can drastically shorten the life! If you look at electrolytic data sheets, they generally have a stated life at a given temperature. Reduce the temperature, and that life increases significantly. Not too long ago, most were rated at 85 celsius. Now, some of the better ones are rated at 105 or 125 celsius. That is better in terms of life, you still need to determine how they will behave in your system, though most of the high temp ones are also very low ESR and hence may make a good power supply capacitor.

I am sure your new cap bank will sound better. Several audio manufacturers have replaced large electrolytics with many smaller ones. Lower ESR and better high frequency characteristics.
Your new cap bank looks good.


P.S. You must have a machine shop at home, you have got most of us jealous.
Your design looks very sexy

Your design looks very sexy. You may wish to solder wires onto the capacitor to increase the thickness of the Copper.

What I did was to use 2 copper sheets, and make large/small hole patterns + use spacers. That way I had .5mm Cu to handle current. I was further able to fold these plates so as to get very short distances to output devices.

I notice that you are using rectifier bridges. Shame on you! Get into some Hexfred's. I decided to standardize on 16ETH06 -- check out the specs at, but if you are using low voltages, go with Schottky units!

Qudos to you for doing the right thing while keeping the thing looking great!

Thank you all for your kind comments and advice.

I checked IRF site and I found 15ETH06 (16 is not listed). It's 15A diode. I had bad experiences before with blowing rect. bridges at turn on (I'm using thermistor as inrush suppresor). In your experience is 15A enough and what is the difference in sonics when compare regular bridges and Hexfred's?

Peter Daniel
i think nelson pass has mentioned that high speed diodes (e.g. HEXFREDS) for rectifiers are not necessarily desirable, he prefers traditional bridge rectifiers as long as you put a capacitor across each diode to reduce noise across the device. however, others have argued that it's not the speed but the soft recovery of the HEXFREDS that make them desirable. i've personally used HEXFREDS in my amps (always with a decoupling cap across them) and i think they "sound" excellent, but i've never A-B compared them to more traditional diodes. i have a feeling that if you use a good high-current bridge like HPotter but with a small film cap (e.g. .01uF 50V) across each leg, the difference in perceived sound quality with a HEXFRED or other high-speed type will be very small to none. but that is pure conjecture, what do i know... :p


p.s. is that a PREAMP power supply??? sheesh...

p.p.s. have you tried Nichicon Muse ("Great Supply") caps? i've used them extensively in my projects and think they sound excellent. their durability should be quite good as well, i think most of them have good temperature ratings (105C). i've used them close to their rating limits and they have never failed on me.
Good to see some good Aussie presence over there - teach you Yanks a thing or two !. :D
Yes Peter Stein has made some very nice stuff.
An ME850 running a pair of Duntech Sovereigns was pretty damm impressive in its day !.
Glad that you are enjoying your ME gear.

Regards, Eric.

BTW - heard a story of an owner using an 850 connected to an audio sig generator to TIG weld a couple of thin steel sheets edge to edge and then sent it to Peter.
I understand that he was not impressed that someone should do this to one of his amps - nevertheless this is testimony to ME reliability under extreme conditions !.
Everybody else who heard this thought it was funny - me too.
That's what I used here: Nichicon Super Through combined with regular grade Nichcons GQ. This is Son of Zen power supply. This project is more like an experiment to check how good SOZ really is. Then I will built my reference amps, either Alephs or SOZ with all the good parts I keep for that purpose: Elna Cerafine, Vishay resistors, FRED diodes, silver wire etc.
Sometimes it's hard to draw a line when choosing parts quality. I can buy seemingly good electrolytics and bridges in a local surplus outlet for very little money. Then the question arises: should I use them or spend $300 for new caps, the decision is not always easy.
I have quite a lot of ROE Elko-EYV electrolytics in my box. They look really good but been there for probably 8 years. Should I go for it and use them in my Aleph project or forget about them?

very nice, welding with a power amp... though i can understand peter's disdain at what someone did with one of his babies.

i actually got the ME amp through a small audio publication over here that i review for, Bound for Sound. There was an extra review sample on-hand that needed repair so i fixed it up and bought it from ME. it's too bad ME does not have a distributor over here, i imagine i am one of a handful of ME owners here in the states. a pity considering how nice the amp sounds, better than a lot of "high-end" gear over here costing twice as much. i guess the ME gear does not have the "sexy" looks of a Krell or Levinson or what not, but peter puts his brains and money into what actually counts, solid engineering and good-sounding circuits, god forbid...
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