quality differences in electrolytic caps

[pietro_moog]

hi guys. i know this may be a stupid question, but i need to know:

is there any difference in quality between different brands of electrolytic caps?
i always used sprague on cathode caps, and cheap capacitors for filtering duties.
some people use sprague atoms on filtering, but i never thought about it because they
cost a lot. i was just wondering if they could be any better, i always thought they were expensive because of fashion/marketing reasons.
what do you use?

[Ken Moon]

Bonjourno, Pietro.

To me, the first consideration is physical size and shape - some amps need axial types, some radial, and some use can-style caps.

After that, I look for voltage rating (hardest to find are caps over 450V), high temperature, long life, and low ESR.

Here are a couple of high-quality filter caps:

450V Radials - Nichicon PW series:

http://www.nichicon.co.jp/english/products/pdf/e-pw.pdf

450V axials - Vishay 041-043 series:

http://www.vishay.com/docs/28329/041043as.pdf

For over 450V, you're pretty much looking at F&T or Sprague Atom axials only (except for motor caps, which are rarely used outside of tube hi-fi).

I much prefer the F&Ts - they're smaller, and every bit as good as the big blue Atoms.

Another possibility is to use big film caps like the Solens, which handle 630V, but they are huge, and they give a different tone to the amp than a typical electrolytic.

My favorites for cathode bypass duties (over 1uF) are the Vishay 138AML and 118AHT series, in 25V or 63V ratings. Under 1uF I just use a film cap.

[Chuck H]

And FWIW, to answer the OP, yes there is a difference in performance with quality caps. Poor quality filters can allow ripple into the audio path and fail prematurely, but... One anomoly is that a low ESR isn't always best for every amp. The reasons are complicated but on some designs a not so low ESR actually has a positive effect on tone at the expense of a small amount of ripple when over driving the amp. When I design and build I do use low ESR caps though. Sprague Atoms have been performing poorly on my last two builds and I'm switching to the Nichicon PW series caps. A bit of a PITA since the PW's are radial lead and all my designs have been axial lead. But I can't abide the way Sprague/Vishay is gouging people for a cap of questionable quality.

[Alex R]

I echo Chuck on this. I prefer to use caps that are manufactured in large numbers for lots of different uses. They are going to be more reliable imo than niche-market stuff however expensive. You can find plenty of mass-manufactured caps at 450v or less - easy to spot, they are the cheap ones! If you happen to need 500v rated caps then you are into a more difficult area as they are made mostly for our valve amp niche market. Alas whatever brand these niche market caps are, I see failures with them in a way I don't see with the 450v caps. I have seen new Sprague Atoms fail, and a new F&T cap fail, and I don't use either type any more unless customers ask for them. Where possible I would use caps in series with balancing resistors to get above 450v. However I bought in a stock of TAD-labelled 22uF 500v axial caps - no idea who makes them - and they have been good so far. Same goes for the Illinois 22uF 500v axials I used before, these are Chinese made I think, as probably are the TADs. This is too handy a value for old Fender amps to use series caps. Just my bit of experience for you.

[pdf64]

I understood that F&T made the TAD electrolytics.
F&T seem good quality and performance, and make a 22uF 550v, useful for later SF Fenders that run a little over 500v.
F T Axial Electrolytic 22uF 550V 18x39mm
I can recommend the above supplier for anyone in the EU. Pete.

[Ken Moon]

is there any difference in quality between different brands of electrolytic caps?

I agree with everything the other posters said, but I'm not sure everyone know that all electrolytic caps are not the same.

Even within a major brand such as Vishay or Nichicon, there are dozens of series of electrolytic caps.

The price difference is not that big from the cheapest to the most expensive.

If you don't have to have a particular size (like when you need the leads to fit into the holes on a pre-made PCB), why not go with the ones that have longer life and can handle higher temperatures?

The two caps I listed above, the PW series from Nichicon (radial), and the 041-043 series from Vishay (axial), are the highest quality mass-produced caps I know of, and I've used both many, many times with not a single failure.

The worst thing you can do is buy filter caps from eBay - sure, there are a few good ones mixed in, but there are a lot of the fake caps there (I bought some fake Elons about 2 years ago). Others may be factory rejects.

I'd advise getting filter caps from a major distributor/retailer like Newark, Mouser, Allied and Digi-Key. Their buying practices are such that there is less chance of a fake getting into their stock (they buy huge lots straight from the manufacturer, and can trace lot codes and such if failures arise).

The reported failures of F&T 500V caps are starting to worry me a bit - on my next amp I'll be using JJ can caps in the power amp, and Nichicon PWs for the preamp nodes.

[Chuck H]

Just to add...

Nichicon PW's are available to 450V at the Mouser site but aren't listed in their paper catalog. I spec'd them throughout for an amp I designed for another MFG. The first four prototypes were built with these and do sound better than the later MFG'd amps that used cheaper caps to cut costs. No other difference other than pot taper between the two. Further, I expect the prototypes with the PW's will prove more reliable with age.