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Capacitors - Does size matter?

Lieberung

pfm Member
When designing an amplifier, and you want a total amount of capacitance as a power reserve for the power amp, lets say a total of 50k microfarad (F). Will there be any difference in sonic characteristics between a design using 2 large (25k F) vs another design using 10 small (5k F), when all else is identical and the total F is the same?

Im not a electric engineer, just curious on why some manufacturers (e.g. Accuphase) use few large capacitors in their amps, while most others use smaller, but more.
 
It's historically the way it was done, due to availability of parts, why bother soldering 30 parts into a pcb when one will do it?

The output stage of a big ole amp doesn't care about a few mOhm of series resistance in a 50v rail.

It has become a design fad lately, though there will be rare examples where marginally higher esr could be an issue, ie badly designed digital circuits...etc
 
Thanks for your input. I have read somewhere that big caps generally are more expensive per F and that its more difficult to evenly match few identical caps in F down to decimals for each channel, than matching a pool of several smaller.. Or was it the other way around? Anyways, components cost and practicallity is ofcourse important factors for manufacturers. I was more interested in if there were other reasons. For example would big caps in theory provide better dynamics (e.g. typical in Orchestra music) but be slower to regenerate than several smaller, which might better for other types of music with less dynamic variations in dynamic scale but at a faster tempo (e.g. like rock, metal, techno).
As you say, it might be just marketing or cost considerations.
 
From a ‘Right To Repair’ perspective the less that need to be replaced the more likely the kit is going to dodge landfill. Whenever I see pictures of “high end” audio with huge, huge banks of small capacitors I strongly suspect no one will ever be arsed replacing them in 20-25 years which effectively renders that piece of kit environmentally damaging junk. Great design is way more than trying to extract the final 0.0002% of performance IMO. It is always a ‘whole picture’ view; function, fit, finish, reliability, serviceability etc. It is what separates the classics from the rest.
 
From a ‘Right To Repair’ perspective the less that need to be replaced the more likely the kit is going to dodge landfill. Whenever I see pictures of “high end” audio with huge, huge banks of small capacitors I strongly suspect no one will ever be arsed replacing them in 20-25 years....
Often a lot less than that. Small capacitors have smaller volume and hence shorter lifetime at best. These big banks have to be heavily derated as it is impossible to ensure that ripple current is shared fairly unless you put a resistor in series with each part
 
There is a ton of large capacitors nowadays that are very high performance with very low ESR so I wouldn’t bother having multiple small caps other than for cost or space concern.
And as said, a large capacitor will dissipate heat better than a bank of small ones that are tight in a small enclosure.
 
All aluminium capacitors leak through their rubber seals. More electrolyte means a longer lifetime. Just look carefully at the datasheets from reputable manufacturers like Panasonic and see how the lifetime varies with diameter
 
Less mass so they heat up more, its about the reaction that causes the heat, rather than the heat itself per se. Smaller caps, lower ripple current rating, greater self heating, faster failure. Its an absolute for two same make caps varying only in capacitance.
 
ripplecurrent^2 * esr, is the internal heat generation, basically.

Physically-smaller caps likely have larger ESR, from basic geometry proportional to 1/(radius ^2) - which lies behind davidsrsb's comment - and markedly less ripple-current capacity as a result.
Sticking a bunch of tiny caps in parallel close together is no satisfactory answer - simply because each surrounds the next with am equally hot cap.

Just buy the one good part.
 
I saw some large reservoir capacitors in Naim and Exposure amplifiers still running strong after 40 years, can’t say that with smaller ones with same function.
 
I guess that can volume wasted with the can itself and insulation becomes a high proportion at smaller sizes, leaving less room for the electrolyte
 
As we are talking about ripple, is it as simple to measure as switching my DVM to VAC and measuring across the cap? I assume it is.

Numpty question really :)
 
I saw some large reservoir capacitors in Naim and Exposure amplifiers still running strong after 40 years, can’t say that with smaller ones with same function.

I recently re-capped some 130 or so caps in various 20-40 years old gear and noticed that almost all old lytics had correct capacitance, most of them even a bit higher than rated, and especially the larger ones seemed to be far from end of life.

But after recap everything sounded so much better that I thought it was worth the hassle. Still wondering about the need for recap of those bigger older PSU caps which BTW looked well built and sturdy. Also will todays caps last longer than the old ones...?
 


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