Current handling capability: big F&T power supply caps vs new design Nichicon

[mikepukmel]

If I compare the new design caps Nichicon: 500v 22uf 560ma ripple current etc

https://www.mouser.com/ProductDetail...1z6jN6aA%3D%3D

to the old style F&T

https://www.tubesandmore.com/sites/d...t_ft-a_new.pdf

am I reading the specs right, that the big heavy leaded F&T 500v caps are really 100ma, to 200ma, compared to the Nichicon? The little skinny lead nichicons have over 2x ripple current? Is this good or bad?

Are the nichicon's really suitable for power supply caps in these old tube amps

[Mick Bailey]

Caps have followed the path of many electronic components in getting smaller along with increased performance. The physical size and lead diameter of pretty much everything is reduced. I have no problem at all with using this type of cap in older tube amps and they perform very well. The F&T cap leads are flimsy compared to the old Mallory caps in (say) silver face Fenders, now the Nichicons are thinner still.

Ripple current becomes an issue either when designing a PSU or when replacing capacitors so that the PSU ripple current doesn't exceed the capacitor rating. A cap operated beyond it's ripple rating will have increased temperature and shortened lifespan. Ripple current is related to ESR, so low-ESR caps have better ripple figures - important in high-demand applications such as switch-mode power supplies. Fitting a capacitor with a higher ripple current rating than necessary doesn't harm things - you get a slightly more efficient capacitor that runs cooler, though perhaps not noticeable. I liken this to using 5W resistors in a circuit where 2W would be fine.

There was a time where I never even looked at ripple and you'd have to dig out specs to find out what the value was for a certain cap. In my experience tube amps don't exhibit high enough demands on the power supply for ripple to be a real consideration. Having said that, If I'm shopping for caps at a given price I'll usually pick the ones that offer higher ripple figures - it can be a sign of better construction and durability and often a high ripple cap will have a better thermal rating, but not always.

[mozz]

Best cap does not mean the best sounding amp. F&T's have a good reputation among guitar amp repairers, builders and upgraders. If you look at the specs, they are not the best cap to make the best power supply, they have faults and weaknesses but "I" think they actually improve the sound without making it too sterile.

I mentioned once before, there was a website where they had a good sounding Fender Bassman, they tested the power supply for a bunch of parameters. They then tried to duplicate this power supply with some lab equipment and subbed it into the amp. The sound changed.

Look at some Valcos and Premiers, they used cheap disc coupling caps yet they sound great. You can get those F&T 22/500v for $3.95 or 4.95, i always keep at least 10 in stock.

[Enzo]

And I hate to repeat myself, but...

It is only a guitar amp, tiny little differences in specs is not going to matter in the overall circuit.


"Better" is an illusionary term. What does better mean? Better as in smooths ripple more completely? Better as in sags reliably? Better as in "sounds better"? And so on.

To use another cliche, don't let the cap be a solution looking for a problem. In other words determine if the existing arrangement lacks anything a "better" cap can provide first, then consider replacements.

[mikepukmel]

Thanks Everyone!!
Well, for me, I don't know the physics well enough, so "better" means "it won't blow up in my face because I used new design caps that had a lower frammistan rating". Then, of course, there's the frickazoid adjustment.

I have a friend who did electronics for years, don't get a chance to talk to him much. He said once in passing something about 105C caps ve 85c caps, that unfortunately stuck. So, Im thinking, geez, all these little projects Ive tinkered with, all have F&T caps, let me go look up the rating, and sure enough, they're all 85c.

But then one of you guys on one of the blog posts, mentioned that, heck, compared to 1964 manufacturing technology, the F&T's are miles above, so just don't worry about that, worry about, e.g. lead dress. ...

Cool, so, even not knowing the details of comparing caps, these will probably work fine in this little Supro mimicking project. Thanksa gain.

[Enzo]

Ever notice the doors in places like hotels or schools? The hinges are so much more heavy duty than ones in your home. Same for the latch and knob. That stuff is meant to last years under heavy use. Clearly they are "better" hinges and knobs than ones in your house. yet the home ones have worked just fine the life of the house in many cases 40-50-60 or more years. So what would my home gain if I replaced my lesser hardware with the better stuff? Nothing really. Just my opinion, but when we micro-analyze caps like this, it is a similar matter.

[Leo_Gnardo]

compared to 1964 manufacturing technology, the F&T's are miles above, so just don't worry about that, worry about, e.g. lead dress.

I was recently donated a shoe box full of ancient wax & paper caps. Maybe I'll offer 'em one of these days in our Flea Market. Or go for the big bucks on EepBay or Revoib. "Get that vintage sound at a price you can't afford!" Also have a box full of huge 400V electrolytic "beer cans" from 1966. They oughta make a big hit as they go kablooey when someone tries to charge 'em up, what fun. I'll have to give 'em a go, next 4th of July...

[Gingertube]

Double the ripple current rating infers 1/4 of the temperature rise and MUCH longer lifetime.
I would perhaps use the F&T for repairs to replace F&T purely to keep an amp "original".
I would use the Nichicon for new builds - actually I generally use Panasonic ED for new builds BUT not the F&T.
JM2C
Cheers,
Ian

[Chuck H]

Nichicon convert right here offering his endorsement. I got tired of all the large diameter axial cap shenanigans (fakes on the market, small cap in big can, hiding mediocre specs from the general public and "exclusive" price point). I switched to Nichicon PW's many years ago and have never looked back. Better cap, lower price and easy to source. I think Nichicon makes a longer life cap than the PW, but I haven't tried it yet. Compared to what's in a typical guitar amp the PW's are already miles ahead. I don't even flinch when I have to shrink tube and zip tie things to safely use them in axial applications. Form follows function so it looks fine to me

[NoelW]

Ian & Chuck,

What are your views and experience on, electrolytics, whether 105C is better than 85C (or necessary) or that either will do the job fine?
I have not found temperatures that high in amp chassis, but I tend to buy 105C caps anyway.

I use Nichicon & Panasonic mostly, but also United Chemicon and Rubycon and I have used F&T once or twice.
So far I have not had problems or failures with any of them, but I prefer the Panasonics and the 'cons for their size, over any of the axial caps.

Cheers, Noel

[Chuck H]

"MY" opinion... Well, maybe you can state a spec of 105C no matter how mediocre it's performance at that temperature, as long as you state what it's actual performance is at that temperature. I wouldn't be at all surprised if some caps rated at 105C are no better under such conditions as many 85C rated caps. I think I've actually seen some of that in derate specs. But I don't actually know if there's any stringent criteria for being able to print a 105C rating outside of disclosing performance.

[Gingertube]

105 degrees C rating for tube amps and even then apply a bit of thought to physical placement - where possible place away from heat sources.

Cheers,
Ian

[Enzo]

It isn't that the caps are intended to run at 105 degrees, it is that they will withstand that better.

Your amps seldom get hot enough to boil water.

A 105 will potentially be stressed less than an 85 by whatever heat levels you have.

[Gingertube]

Electrolytic Cap life is dependent on their internal temperature which has a drying effect on the paste electrolyte.

Caps self heat according to Power = current squared x resistance, in this case the current is the ripple current and the resistance is their ESR (equivalent series resistance).

They also absorb heat from adjacent components.

To give some idea about this we see an equivalent idea in aircraft wiring standards, wire rating is based on temperature rise. If 2 wires are bundled together so they can heat each other then the current rating of each wire is reduced to 0.94, if 3 wires bundled to 0.86 etc. Source is Fig 11-5, AC43.13-1B Chapter 11 "Aircraft Electrical Systems".
So don't bundle all your high ripple current caps together (like in Fenders "doghouse") and keep away from other heat sources.

I said above that I use Panasonic ED but have also use Nichicon and Rubicon. Higher Voltage Caps, in general, have higher ripple current ratings. Don't be afraid to use a cap with much higher voltage rating than absolutely required.

Cheers,
Ian

[SoulFetish]

It isn't that the caps are intended to run at 105 degrees, it is that they will withstand that better.

Your amps seldom get hot enough to boil water.

A 105 will potentially be stressed less than an 85 by whatever heat levels you have.

okay, here is how it works:
It has to do with the manufacturers providing a published general "expectancy" of working life for the cap. This is usually stated in hours at it's MAX ambient operating temperature. Another factor which contributes to the working life is it's operating voltage, although less so than temperature.
So, in general, a published working life of *** hours @ 105˚C (or 85˚C) can generally be expected.
Two important things to consider:
first, is that for every 10˚ lower, the capacitor life can be expected to extend by a factor of 2.
Second, if the capacitor's internal temperature is increased more than 10˚ of it's max ambient temperature rating, then the capacitor's life is decreased by a factor as well. The main factor leading to this is caused by the capacitors ESR dissipation due to high ripple current.