Advances in Electrolytic Caps

[fiftynine]

Sprague Atom 16uf 475v is 7/8" diameter x 1 5/8" long and five times the price of a Shiang Chen (SC Taiwan) 16uf 450v that's roughly 1/2" diameter x 1" long.

What gives?

[sluckey]

The actual Atom cap is really about the same size as that cheap Asian cap. It costs 5X as much to stuff a tiny cap inside that big ole Atom shell. 

[fiftynine]

Indeed. I've split an Atom and it's about a 3rd full. The internal assembly however, is still 2-3 times the volume of the cheaper ones, like for like. The far east factories could quite easily clone a Sprague for size.

So is it the compact consumer electronics demand that's made them smaller? And if they perform as well as the biggun's, why waste space and money if the cheaper ones won't fail in guitar amps.

[6G6]

I think at least part of the larger than needed size thing has to do with expectations.

[Willabe]

So is it the compact consumer electronics demand that's made them smaller?

I would say yes that's what happened. Through the years they developed better electrolyte compounds and better/thinner insulator (plate) material. Some/many of the insulator (plate) materials are now etched for more surface area.         

And if they perform as well as the biggun's, why waste space and money if the cheaper ones won't fail in guitar amps.

For 2 main reasons,

1. Traditional vintage look.

2. They fit the eyelet/turret board size/spacing.


                        Brad   

[kagliostro]

For the same reason I prefer to use 2W metal film resistors (and also because if they are smaller I have difficulties to read values  )

---

May be a larger capacitor has the benefit of a better heat dissipation ?

K

[HotBluePlates]

Sprague Atom 16uf 475v is 7/8" diameter x 1 5/8" long and five times the price of a Shiang Chen (SC Taiwan) 16uf 450v that's roughly 1/2" diameter x 1" long.

What gives?

It may sound silly, but I'd use a modern cap with a name ending in "con" (Nichicon, Rubycon, United Chemicon, etc) or Doug's F&T caps.

That said, there is an astonishing variety of electrolytic caps out there, and not all are the best at everything. Vishay and CDE have some very good pages of cap data sheets (like an 80-page list) that detail how some series are optimized for certain applications.

I think at least part of the larger than needed size thing has to do with expectations.

Atoms weren't made for the guitar market (though the guitar market may be keeping them around now). They were made for the "military renewal" market.

Say you have a piece of government- or military-owned electronic equipment. There is a set specification (including size) for every part inside. Most items have a set space for a cap to occupy (length, diameter, axial or radial leads, lead thickness, etc) especially if there are circuit cards inside. The piece of gear might stay in service 30, 40, 50 years, especially if it does the needed job and acquiring new equipment is more costly than maintaining old equipment.

So gov't/military needs replacement parts with the same form-factor as the part they're replacing. I imagine if I cut open an old Sprague Atom from the 70's (with the orange case covering), the entirety of the inside is filled. But the renewal market demands the case and leads stay the same size today as when the gear was made 40 years ago. So Sprague packages a smaller modern cap inside the bigger housing that maintains the form factor.

[alerich]

And if they perform as well as the biggun's, why waste space and money if the cheaper ones won't fail in guitar amps.

I don't use Sprague Atoms in my new builds. Never have, actually. I have had excellent results with Illinois and MIEC caps. I see Doug is now stocking F&T axial E-caps. I may try those, too. If I am recapping a vintage Fender amp for someone else and they specify Sprague Atoms and approve the cost, that is what I use.

[fiftynine]

Thanks for the input. I agree with the comments it's traditional and expected. The Mil Spec point, too.

But I can't justify that in a modern build and a new design. Compromising other elements to accommodate five 1" x 2" cylinders when it's not needed is nonsense.


Heat dissipation is a good point, though.

[sluckey]

A properly functioning electrolytic cap does not produce any heat. If you find one that is producing heat you should replace it.

[SILVERGUN]

A properly functioning electrolytic cap does not produce any heat. If you find one that is producing heat you should replace it.

Do you think that the extra wrapper room on an Atom cap might provide any additional heat rejection?...or somewhat of an insulation factor?
...making it somewhat less susceptible to heat exposure issues than other cheaper caps?

...making it a "better cap" for having that quality?

[PRR]

My brother's 1941 Plymouth has a 700 pound engine of 200CID making 72 horsepower.

My 1979 Ford had a 550 pound engine of 351CID making 144 horsepower.

My 2002 Honda has a 200 pound engine of 140CID making 148 horsepower.

I suspect the Ford and Honda are very similar cost-to-make, in a well-run factory. (The Honda is half the cylinders in alloy block, same number of smaller valves....)

Big engines are known for "slow grunt", but allowing for the vast difference in car and gearing, the Honda has wider better power-band.

I just replaced my hot-air furnace. The old blower used to start with a wwHHHuGH!! and dim the lights. The new blower comes up silently and no strain on the electric.

Things can change, "advance", even improve.

(And sometimes not. Modern affordable electric chain-saws are no match for a 40 year old Craftsman.)

> A properly functioning electrolytic cap does not produce any heat.

They do in *severe* service, making BIG rough power. Welder and motor supplies.

The ripple current times the ESR is a loss and a heat.

Audio amplifiers are far-far out of that zone. By the time we have enough capacitance to smooth our DC we have much more physical size than we need to dissipate the heat.

And the physical size goes down because of improved foils, which also reduces the ESR and ripple-current heat.

They did that to cut size and *cost* of power supplies generally.

Your best bet for new designs is "snap-caps".



Among other things, they are sold into those welder supplies. They have to have low losses and sturdy dielectric to withstand the massive currents and the cabinet heat. It is a very competitive market: Lincoln will cancel a deal with Joe-Con if Joe's caps turn out to have higher warranty returns than Fred-Con's caps.

[SILVERGUN]

Among other things, they are sold into those welder supplies. They have to have low losses and sturdy dielectric to withstand the massive currents and the cabinet heat. It is a very competitive market: Lincoln will cancel a deal with Joe-Con if Joe's caps turn out to have higher warranty returns than Fred-Con's caps.

And the best news about that is I can get em at 30% off list.

Haven't looked hard enough but I've rarely seen values that cross over easily, without being overkill, or huge.

The tank caps in our induction heater are about 3" around....they'll take 475V and give me 2700 usable ufs, but I cant squeeze em in an amp chassis.

I'll look harder now that you mention it.

[HotBluePlates]

... The Mil Spec point, too. ...

Being recently out of the military, "mil spec" is not the promise of super-high-quality marketers would lead you to believe.

"Mil-Spec" means the part meets the criteria established in a specification document. Now, if you have 1 manufacturer or 50,000, all can have the given part labeled with the same mil-spec #, which greatly simplifies logistics and procurement, as all notions of cross-referencing individual companies' part numbers are out the window. The burden is shifted to the manufacturer to get their part recognized by a supply agency and incorporated into the supply system.

So the spec makes sure the item is only as good as it needs to be for the intended job; if it was "too good" it would probably cost too much money. So the military specifies different characteristics for say, a pot, that doesn't need to be 2w, sealed and have gold contacts for less-demanding applications. Saves taxpayer money.

Having driven HMMWV's ("Hum-Vee's"), no one in their right mind would want one for driving on a paved road. 9 miles per gallon on diesel; tiny, cramped, uncomfortable seats; no radio & barely-functioning a.c.; ~55 mph top speed with the engine & transmission screaming-loud (to the extent the military is supposed to wear earplugs plus over-the-ear hearing protection... But if you need to go off-road, cross 4ft ditches, drive along the side of fairly high-slope hills and ford 6ft of water, they're great. That, and we weren't paying for any fuel...

Anyway, just trying to add perspective in place of hype.

[jojokeo]

It is a very competitive market: Lincoln will cancel a deal with Joe-Con if Joe's caps turn out to have higher warranty returns than Fred-Con's caps.

Joe-Con is now Joe-Tung