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Thread: Low Impedance Electrolytic Capacitors in Power Supply: Advantages? Disadvantages?

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    Low Impedance Electrolytic Capacitors in Power Supply: Advantages? Disadvantages?

    Just wondering if there might be any advantages or drawbacks to using the low impedance E-lytics in my Twin Reverb.

    Like this one, for example:

    Nichicon

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    Senior Member ThermionicScott's Avatar
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    Electrically, they're great. The ones in your link are radial-leaded, so make sure you order carefully.

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    Thank you, TS. So, nothing weird will happen in this application. Radial leads is the only way to get these, I think. Not a problem for me.

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    Old Timer tedmich's Avatar
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    The ESR of caps in linear power supplies is very seldom an issue, an additional benefit to these is their price and the fact that they are rated for ~22 yrs of service at 1h a day.
    They represent a much better deal than Atom axials (TVA1620-E3) which are only rated to 85C, with no lifetime data, for 550% more, $16.53!

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    ... which is why I HAD TO ASK... Seems too good to be true.

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    "Thermionic Apocalypse" -JT nickb's Avatar
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    Quote Originally Posted by Krwkka View Post
    Just wondering if there might be any advantages or drawbacks to using the low impedance E-lytics in my Twin Reverb.

    Like this one, for example:

    Nichicon
    Those are 100uF 350V with a 290mA ripple current rating. An Atom TVA1718 100uf 450V is 800mA. The ripple current rating is very important and if exceeded the core temperature of the cap rises and failure soon follows. At the very least life is dramatically reduced. The ripple current in the cap is typically more than twice the average DC load current in a linear full-wave power supply.

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    Last edited by nickb; 02-11-2016 at 09:21 PM. Reason: 350V not 35V!!
    Experience is something you get, just after you really needed it.

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    Old Timer tedmich's Avatar
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    The Nichicon cap is a fair price/performance ratio, its the Atom's profitability that's "too good to be true" for Vishay IMHO

    Leaded caps in general will be going away, so snap in and then SMD caps will need to be in the Twin Reverbs of the next couple decades...

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    Senior Member ThermionicScott's Avatar
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    Quote Originally Posted by nickb View Post
    Those are 100uF 350V with a 290mA ripple current rating. An Atom TVA1718 100uf 450V is 800mA. The ripple current rating is very important and if exceeded the core temperature of the cap rises and failure soon follows. At the very least life is dramatically reduced. The ripple current in the cap is typically more than twice the average DC load current in a linear full-wave power supply.
    I don't often consider the ripple current rating, but perhaps I should. (Most of my amp stuff is derivative of existing designs.)

    Since the Twin Reverb uses two caps in series at the first position, do we get to double the ripple current rating, or are we not so lucky?

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    "Thermionic Apocalypse" -JT nickb's Avatar
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    Quote Originally Posted by ThermionicScott View Post
    I don't often consider the ripple current rating, but perhaps I should. (Most of my amp stuff is derivative of existing designs.)

    Since the Twin Reverb uses two caps in series at the first position, do we get to double the ripple current rating, or are we not so lucky?
    The current is the same in both caps. Sorry, you didn't get lucky.

    But as Tedm points out, they are cheap so you can put an extra one in parallel with each. The current is now shared so the ripple current rating of the pair is 2x that of one, you also get half the voltage ripple and still have money left over for a couple of beers. So you do still win after all

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    Old Timer tedmich's Avatar
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    Yes ripple current can be important!
    https://maaplibrary.files.wordpress....chapter-58.pdf
    Most modern caps should easily handle guitar amp ripple currents (especially if they use tube rectification ) but the calculations should be made to be sure.

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    Twin Reverbs us solid state rectification.

    NickB: I was looking for the specs on the Atoms. Where did you find that? (It's as if the manufacturer wants to keep the Ripple rating a secret!)

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    Last edited by Krwkka; 02-11-2016 at 11:07 PM.

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    Quote Originally Posted by Krwkka View Post
    Twin Reverbs us solid state rectification.

    NickB: I was looking for the specs on the Atoms. Where did you find that?
    This is all I have. Actually, this is all they have since it's what I got when I asked them directly.

    As a rough guide, if the cap is getting more than just warm, the ripple current is too high. A cap's ripple current rating is closely related to how well it can dissipate the heat the current generates. The lowest temps will be on the surface but the core will be much hotter. The life halves with every 10C rise in temp.
    Attached Files Attached Files

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    Old Timer tedmich's Avatar
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    The relationship between working voltage, current and lifetime is the way cheap axial caps (Ruby?) get to claim 500VDC ratings without any lifetime data. All caps can be run at higher than conservative voltage ratings, the trade off is lifetime. The same with ripple current, a 47uF cap rated at 500VDC with 1A ripple current is relatively easy to make with a <1000 hr lifetime...
    https://www.parts-express.com/ruby-g...citor--020-670
    no such thing as a free lunch etc...

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    Thank you for that, Nick my man. I'm a bit suspicious of those boys at Vishay because, as TedMich alludes, the specification is incomplete without a lifetime rating. Then there's the 85 rating on the Atom. Comparing that to the Nichicon above with 105 and 8,000 hrs. !! I dunno.

    Of course, either one of these would probably outlive me in this amplifier ... I just want to put something different in there to, you know, rattle the cages of my buddies with their insistence on using the "proper" "vintage-correct" components.

    I think I'm going to try the Nichicons for the fun of it (and I'm cheap — I should mention that).

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    Quote Originally Posted by Krwkka View Post
    ... I just want to put something different in there to, you know, rattle the cages of my buddies with their insistence on using the "proper" "vintage-correct" components...
    Those buddies will be horrified to know that a small modern chunk of capacitor guts is inside the "vintage-correct" size Atom cap case.

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    Bent Member Chuck H's Avatar
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    The Atom's have been around for a long time. I don't know if the construction of them has changed. I do know that it's only in the last decade that people report the "tiny cap in a big can" thing. I vaguely recall someone cutting open an old one and a new one and they were indeed different. I mention this because, like many tubes made today, it's possible the "specs" for the Atom caps is grandfathered in, but is actually a spec for the older design.?. Just "spec"ulating (yuk yuk)

    Regardless of that... The lack of a life spec is something I always found suspicious. I mean, if you fail to promise the product will last then it's pretty easy to bump a spec idn't it? Also, the 85* temp rating. As mentioned, this will have an affect on that ripple current spec. The Nichicon is rated at 105*. I wonder how the Atom would spec at 105* in it's 7000th hour

    Nichicon is a very good product. I stopped using Atom caps and Orange Drops because of their stupid high price. I mean, those products do have a little bit of celebrity draw, but at some point you gotta say "That's enough gouging, get the "F" outta here." That, and I was occasionally getting Atom's that would under perform when new or soon after installation. Some would "burn in" and be ok, others wouldn't. So I've been using the Nichicon PW's for about six years. And guess what.?. No more new amps humming like they don't know the words or making sum/difference notes like a ring modulator. Now, I'm not a repair tech or an amp company. I only build a few amps for people that ask me to. But I've used the Nichicon PW's in three new products and three repairs (one recap was an older amp I built sixteen years ago with Atom's) and I spec'd them for a design I worked on with a major manufacturer. So, for whatever my part is, I'll endorse the Nichicon PW's.

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    Quote Originally Posted by Chuck H View Post
    The Atom's have been around for a long time. I don't know if the construction of them has changed. I do know that it's only in the last decade that people report the "tiny cap in a big can" thing. I vaguely recall someone cutting open an old one and a new one and they were indeed different. I mention this because, like many tubes made today, it's possible the "specs" for the Atom caps is grandfathered in, but is actually a spec for the older design.?. Just "spec"ulating (yuk yuk)


    One of many in a 2013 thread over at our friendly neighbors The Amp Garage.

    http://ampgarage.com/forum/viewtopic...5d2794a244456e

    In case you decide to have a look & encounter any blarney from Google - "caution malware site" like that, just push past the well meaning guards & peep all you want, there's no malware. Someday TAG will get this fixed...

    Lately I've been experimenting with film caps for hi voltage power supplies. Lifetime factor just about forever. Pain is rectangular form factor, sometimes takes ingenuity (I hope I have) to fit securely. Full price, many compete with Sprague Atoms cost, and sometimes you can find films on close-out sale deeply discounted. I got about 35 x 30 uF 800 & 900V less than $5 each from Newark. So cheap my Scottish genes are dancing the highland fling. Happy hunting, & don't get shocked.

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    Bent Member Chuck H's Avatar
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    Quote Originally Posted by Leo_Gnardo View Post
    my Scottish genes are dancing the highland fling. Happy hunting, & don't get shocked.
    Well, I can't promise anything. Is the highland fling shocking?

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    "Take two placebos, works twice as well." Enzo

    "Now get off my lawn with your silicooties and boom-chucka speakers and computers masquerading as amplifiers" Justin Thomas

    "Being born on third base and thinking that you must have hit a triple is pure delusion!" Steve A

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    Old Timer Leo_Gnardo's Avatar
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    Quote Originally Posted by Chuck H View Post
    Is the highland fling shocking?
    Only if it's dry & cold, and you wear a polyester kilt and no underclothes. HOOOOT MON! Ai-yi-yi caramba!

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    The PW datasheet indicates 350mArms 120Hz ripple at 105C for 100uF 450V, if that provides some comparison to an Atom part.

    Some other aspects are that a 105C speced cap (such as the PW) would have a higher ripple current capability at 85C, as it could cope with the internal temp rise.

    The life hrs rating and temp rating are the main indicator of service lifetime, where arrhenius type improvements kick in for a normal amp not operating anywhere near the ripple and temp spec conditions.

    If you are keen, then using PSUD2 would quickly indicate the likely rms current experienced by the cap.

    For your use, the low impedance doesn't mean anything really. That moniker is related to the part having specs at 100kHz, to provide a smps designer with some assurance of the impedance at such a high frequency - although the datasheet doesn't actually show any generic impedance curve plots :-(

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    Senior Member ThermionicScott's Avatar
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    +1 on the film caps if you really want to drive your vintage-correct buddies up the wall. I'm strongly considering going that direction once I've used up my current stock of electrolytics.

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    Quote Originally Posted by trobbins View Post
    ... a 105C speced cap (such as the PW) would have a higher ripple current capability at 85C, as it could cope with the internal temp rise.

    The life hrs rating and temp rating are the main indicator of service lifetime...
    For your use, the low impedance doesn't mean anything really.... :-(
    Very helpful, TRobbins.

    Film caps look interesting — but I'm thinking I'll go with the Polyester Kilt type.

    Reminds me of my old friend Glenn's father, Alex who was fond of saying, "Yah, lad. Just watch yerself, baby-oh, or I'll piss up yer Kilt!"

    Thanks to all who chimed in!

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    Radial new production caps are the way to go. Forget about those huge crappy axial caps.
    Speaking of Nichicon which are one of the best you can get some of them with 10 thousand hours guaranteed and that is at 105 degrees (Celsius of course).

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    We did.

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    Senior Member ThermionicScott's Avatar
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    Quote Originally Posted by Gregg View Post
    Radial new production caps are the way to go. Forget about those huge crappy axial caps.
    Speaking of Nichicon which are one of the best you can get some of them with 10 thousand hours guaranteed and that is at 105 degrees (Celsius of course).
    Perhaps we should start encouraging the use of radial-leaded power resistors too. I hate the look of big axial-leaded power resistors wired to eyelets or turrets that are too close together for elegant placement.

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    Perhaps we should start encouraging the use of radial-leaded power resistors too.
    This is not a bad idea. I've seen them in Marshalls and other amps.

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    Bent Member Chuck H's Avatar
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    Hey! Slow up now... What about us guys that don't build PCB? I only use radial caps as a concession. Because the good and affordable caps are all radial now. I don't want to kludge a method for radial resistors too.

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    Senior Member Malcolm Irving's Avatar
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    In some old juke boxes the electrolytics weren't just can-caps, but had pins coming out the bottom which fitted into octal tube sockets. That way the service engineer could try swapping the caps instantly, if the thing was buzzing or humming!

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    Old Timer tedmich's Avatar
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    Quote Originally Posted by Malcolm Irving View Post
    In some old juke boxes the electrolytics weren't just can-caps, but had pins coming out the bottom which fitted into octal tube sockets. That way the service engineer could try swapping the caps instantly, if the thing was buzzing or humming!

    like this?

    Click image for larger version. 

Name:	O-OctalBaseCan.jpg 
Views:	152 
Size:	11.0 KB 
ID:	37785

    relays too

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    Senior Member Malcolm Irving's Avatar
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    Let's bring those back! We could be cap-rolling as well as tube-rolling!

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    Bent Member Chuck H's Avatar
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    Quote Originally Posted by tedmich View Post
    relays too
    Mouser was still selling screw terminal octal sockets about ten years ago. I don't know about now. And you can still get socket relays, but you need to buy the special, rectangular sockets they fit.

    EDIT: Ok... Check it out $$$!

    http://www.mouser.com/search/refine....&Ntt=135206977

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    Last edited by Chuck H; 02-14-2016 at 05:55 PM.
    "Take two placebos, works twice as well." Enzo

    "Now get off my lawn with your silicooties and boom-chucka speakers and computers masquerading as amplifiers" Justin Thomas

    "Being born on third base and thinking that you must have hit a triple is pure delusion!" Steve A

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    Old Timer Leo_Gnardo's Avatar
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    Quote Originally Posted by Chuck H View Post
    Mouser was still selling screw terminal octal sockets about ten years ago.
    I wuz gonna say: intended for plug in relays, but you can use 'em for tube experimenting.

    Or caps, whatever you want to stick on an octal header. Those you can get at Antique/CE.

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    Old Timer tedmich's Avatar
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    And you can "can up" multiple caps for octal sockets just like people do for the glass-> silicon rectifier conversions.

    You could probably do something like the Egnater Randall MTS modular amps entirely with octals!!

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    Senior Member ThermionicScott's Avatar
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    Quote Originally Posted by Leo_Gnardo View Post
    I wuz gonna say: intended for plug in relays, but you can use 'em for tube experimenting.

    Or caps, whatever you want to stick on an octal header. Those you can get at Antique/CE.
    I've got a big box of octal relay sockets, but wasn't sure if they were heat-rated for tubes or not.

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    Old Timer Leo_Gnardo's Avatar
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    Quote Originally Posted by ThermionicScott View Post
    I've got a big box of octal relay sockets, but wasn't sure if they were heat-rated for tubes or not.
    No problem with preamp tubes. As long as you're not running outputs/rectifiers at roasty temps you're likely OK. I've seen some photos of hifi breadboards on Audio Amateur, looks like an explosion in the spaghetti factory, works for them. Also, bulbs up please; inverted power tubes yes you'd be looking for trouble.

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