Hi,
 I bought some JJ 47uF 450 Volt electrolytic capacitors to use in typical CRC PSU type design, and when they arrived they were very small in comparison to what I expected.
They Were just over 1" tall and 1/2 diameter.
Usually I would expect to see a size of 2" tall and 1 1/2" diameter for this size cap.

In the image is the small 47uF 450V next to a 50uF 500V (JJ also) The capacitance/voltage ratings are relatively similar and presumeably to swap these in a less than 400V enviroment is acceptable. I can see that the larger cap has 2 x 50uF - but it is still appreciably bigger than 2 of the small one !

My question is - Is there anything to be gained (or lost) by using the physically bigger (or smaller) type of capacitor.

I am referring to the PSU powering of audio type circuits - presently building the EQP1a.

I have searched the Power supply meta with no answers and obviously a search for capacitor brings floods of results so apologies if I missed the answer to this question.



Thanks in advance  ;)
« Last Edit: November 20, 2009, 09:10:02 AM by schlamn »


hobiesound

Re: Physically Larger capacitors Vs Smaller capictors question ???
« Reply #1 on: November 19, 2009, 02:59:17 PM »
bigger caps usually have a lower esr value than smaller caps. at least that's the case when i look up the data when ordering. bigger caps usually also have a higher voltage rating but that's not always the case.

greetings,

Thomas

JohnRoberts

Re: Physically Larger capacitors Vs Smaller capictors question ???
« Reply #2 on: November 19, 2009, 03:15:48 PM »
It is difficult to make general assumptions about different technologies. Thats why they print data sheets.

Typically the smaller capacitor will be a newer technology, so in general newer technology will improve some aspects perhaps slide on others if trying to reduce cost along with size.

If you have them both in front of you there are bench tests you could perform. One that might be interesting is form a simple voltage divider with the two, then hit it with a (low voltage) waveform at frequencies of interest. Any dramatic deviation from an in phase sine wave ant the junction of the two, will point toward which is different and how.

Keep the driving voltage modest at higher frequency so you don't run too much current through the caps.

JR
Don't only half-ass tune your drums. Visit https://circularscience.com to hear what properly "cleared" drums sound like.

gemini86

Re: Physically Larger capacitors Vs Smaller capictors question ???
« Reply #3 on: November 19, 2009, 03:58:01 PM »
I've found some of those big (vintage) looking cans are just a modern cap put into a larger bucket, to maintain the look of the equipment that it's going into... may not be the case here, but I've seen it a couple times. (mostly chinese knockoffs)




edit: poor english (it's part of being an American idiot)
- Rodney

"...you better call Kenny Loggins, 'cause you're in the danger zone."

Re: Physically Larger capacitors Vs Smaller capictors question ???
« Reply #4 on: November 19, 2009, 04:56:56 PM »
Hi,
 Thanks for replies...

Searched for Datasheets and could only find the larger 1 - not really a datasheet, but from JJs site ...

Type/        Rated uF/ Rated Vdc/  Dimensions/ max. tanδ at  Iac mA

TC 529       50+50       500          35 x 50        0,20          200+200   *****Big Cap

ANH 0475011   47        500           25x42         0,18             160       *****Lil Cap (closest value for a smaller similar sized cap)

ah ha - "tanδ" sounds abit phasey to me !!

So I did as you said John and formed a voltage divider with the pair. gave the highest 1 Khz voltage I could get from my little gen - 25 Vpp  (8.8Vrms)
scoped the input and the junction showed me a deviation of the crest of the sine wave of ~50uS (microSecs) later. (This was hard to judge accurately). The Vpp was about half at the junction - preseumably that is to be expected.

Winding down to 100Hz seemed to bring the waves almost together and going up thro 5k to 10Khz seemed to bring them together also ??

Not sure what this means ?
 
So I charged both caps up to 5VDc.. (Actually both of the dual 50u and the wee 47u). left them standing for 5 minutes and very quickly measured the Dc on them.....

The large ones were at 4.65/4.60 - and the wee one 4.35.. so it was discharging a little quicker.

All this tells me is there are differences, but I am not sure how this will effect the audio in say the pultec I am presently building ?

Hmmmm...

JohnRoberts

Re: Physically Larger capacitors Vs Smaller capictors question ???
« Reply #5 on: November 19, 2009, 05:05:02 PM »
Perhaps a miscommunication but I said to avoid large voltage.

Your generator may be current limiting.

This test will show differences... of any flavor... if they phase shift wrt input one is inductive or higher ESR

JR
Don't only half-ass tune your drums. Visit https://circularscience.com to hear what properly "cleared" drums sound like.

Re: Physically Larger capacitors Vs Smaller capictors question ???
« Reply #6 on: November 19, 2009, 05:10:27 PM »
Oops didnt realise that 8Vrms was large !  I had to wind it up to get some picture on the scope ( nice clean sine waves)..nothing died anyway.

abbey road d enfer

Re: Physically Larger capacitors Vs Smaller capictors question ???
« Reply #7 on: November 20, 2009, 03:51:56 AM »
These caps don't seem to have a much different size/value ratio since one is a dual, the other a single...
tanδ is an essential indication of the quality of a cap, gives an indication of how much losses it could generate. They are very similar in that respect.
Who's right or wrong is irrelevant. What matters is what's right or wrong.
Star ground is for electricians.

Re: Physically Larger capacitors Vs Smaller capictors question ???
« Reply #8 on: November 20, 2009, 07:42:20 AM »
These caps don't seem to have a much different size/value ratio since one is a dual, the other a single...

I appreciate the picture does not show the different sizes too clearly..

In fact the volume of the larger dual one is ~ 48cm³ (2.9inch³) and the sml one is 7.6cm³ (0.47inch³).  

That is 6 x larger (not double !)

However I am picking up that ppl here are not shouting out about any obvious significant differences Esr aside.

As a side note the Large Dual costs over 3 x the price of the sml one.

Thanks for the replys  :)
« Last Edit: November 20, 2009, 07:44:26 AM by schlamn »

Re: Physically Larger capacitors Vs Smaller capacitors question ???
« Reply #9 on: November 20, 2009, 12:58:14 PM »
I used the Weber version of that JJ in my Pultecs.  They've worked great so far.  Though I haven't done any direct A/B comparisons, I would suspect the bigger ones might give a little more output voltage bump in the PS.  As for performance under situations of high current drain they may have a little more reserve 'juice'.  In the Pultec circuit of course that's not an issue.

These were assumedly designed with guitar amp PS use in mind.  At just under 10 bucks they're a real bargain compared to CP custom cans $30 and up for lesser capacitance values.  At 500V you have a nice safety margin in case you're walking the line with diode rectifiers and a hot winding. They make for a much neater build than axials which are kind of clumsy on standard turrets.


canidoit

Re: Physically Larger capacitors Vs Smaller capacitors question ???
« Reply #10 on: November 20, 2009, 05:07:50 PM »
Interesting question!

Does anyone know if the bigger cap means better heat dissipation, longer life or smaller tolerance?????
iva dunit formerly known as canidoit

jdbakker

Re: Physically Larger capacitors Vs Smaller capacitors question ???
« Reply #11 on: November 20, 2009, 05:18:32 PM »
Does anyone know if the bigger cap means better heat dissipation, longer life or smaller tolerance??

It is difficult to make general assumptions about different technologies. Thats why they print data sheets.

JDB.


 

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