Thread: Does size matter? Capacitors - few big vs many smaller

Capacitors is a vital part of an amplifier
Some amplifier brands only use a few big capacitors (Accuphase typically) while most others choose smaller caps in size but more. If the total capacitance is the same, does capacitor size affect how amplifiers sound? Lets say an anmplifier with 2 x 50k μF caps vs an amplifier with 10 x 5k μF.

Thanks for your answers. I see now that I posted this under the wrong category. Should have been in Amplifiers or general audio section.. oh well.

My hypothesis is...it depends. Reason I say this is that there is almost always more than one way to provide or mediate a transfer function, y=f(x) that drives a functional response. And, all audio devices mediate one or more transfer functions.

From a systems engineering perspective, what the designer is trying to do, is use control factors to obtain optimal functional response of the performance transfer function(s) in the presence of noise factors. Control factors could be the type, composition, value of say, a resistor, capacitor, inductor, rectifier, diode, gain device (e.g. tube or transistor), or any combination of those attributes.

Noise factors here are not "noise" in the sense of what we normally think of (what he hear), but noise in the statistical & systems engineering sense: a factor or factors that adds variance and/or shifts the functional response off-target).

Altschuler's Theory of Inventive Problem Solving (aka, TRIZ), teaches that there is almost always more than one way to mediate a transfer function. One wants to choose or implement the transfer function in a way that achieves the optimal response (either in a maximal or minimal direction, or "on-target") while remaining robust to the impact of noise factors.

Examples of noise factors in circuits could be things like the tolerance value of resistors, performance of resistor based on composition, core saturation of iron-core inductors, impact of heat or vibration on performance of transistors, semiconductors or crystal oscillators, etc.

Then there's the bugaboo that results from the fact that most all engineers were taught OFAT at University: One Factor At a Time. Take, say, 3 control factors (aka "knobs"). Set one of them to a value with the others at "zero" or some standard setting. Turn Knob A to 100, measure. Reset it, then turn Knob B to some value, measure, and so on and so forth. This is the "basic scientific method" The big problem with OFAT is that it does not consider, examine or characterize the influence of INTERACTIONS. And interactions are very common in chemistry and physics. The Time*Temp interaction is a very common one that we all know about (even chefs know about this when cooking), but the the importance, influence, and frequency of interactions is not generally taught with rigor at Uni.

These are all things that bear consideration by the designer or engineer. And there's usually multiple ways to manage all these factors, the control factors and the noise factors.

So, the answer to the original question. Which is better: fewer big caps or greater number of smaller caps is: it depends.

A good engineer will understand the functional requirements well enough to be able to make a decision as to what is the best way to implement the transfer function as effectively as possible to obtain the desired functional response while having the system robust to the impact of noise. The best way to do this is by using a statistical approach based on ANOVA called "Design of Experiments" (aka DOE). DOE will let the engineer examine all the control factors, all the possible INTERACTIONS, and determine the impact of noise on the response. As well as produce a surface response plot, if required.

Shown here is a DOE I did some years back to determine where to set the controls of my REL sub (gain, XO, phase, etc) to integrate the sub optimally with my 2-channel Mains.

The ANOVA table for the DOE:


A surface response plot at a 155 Hz node


The above is an example of setting up a subwoofer, but same principles apply and can be used to any engineering objective, e.g. the performance of a circuit or components in a circuit topology, or...capacitor designs in an audio component.

Oh boy… I think I need a drink

Thanks for all replies. Im humbled by your knowledge. As most things in engineering its about compromises and it depends on what you are trying to acheive and whats most important.
I have read somewhere that big caps may provide more slam or dynamics, and having smaller caps provide more agility, faster response, just like Mr. Peabody wrote in his post above.
As an example, Accuphase has the last 20 years always used two big caps in their integrated and power amplifiers, and they are known for a smooth and laid back sound but with good dynamics, excelling at Orchestral music, classical, rock, jazz and blues etc very life like, but maybe not managing 'faster' stuff like metal with lots of double bass drums. Some might disagree..

Just curious if by looking intside an amp and its components, you could determine some of it musical qualities.

a] there are good amplifier designs with large capacitors.
b] there are poor amplifier designs with large capacitors.
c] there are good amplifier designs with small capacitors.
d] there are poor amplifier designs with small capacitors.
e] there are good amplifier designs with silver cases.
f] there are poor amplifier designs with silver cases.
g] there are good amplifier designs with black cases.
h] there are poor amplifier designs with black cases.

My point is, capacitor size is not a criteria for good amplifier design.

Actually it probably comes down to these (and other) factors:
a] enclosure profile height.
b] cost per microfarad.
c] manufacturing assembly costs.

It's not a very simple question to answer. There are many factors involved and come into play. There are different types of capacitors and they can and do behave differently when it comes to ESR or "equivalent series resistance" and frequency of operation. They act different depending on the frequency of the application and circuits. RF circuits will see a different set of variables than an audio amplifier when it comes to ALL measurements.

The main criteria for Audio Amplifier capacitor banks are to store and to smooth the DC as well as provide bursts of current into the lower impedance that is created by the speaker as it reproduced various frequencies. (Yes, that fancy AC that came in on your fancy power cord has been rectified and converted to DC to be stored and then used on the "voltage rails" to deliver instantaneous bursts of current when the speakers says "I need that burst of current for that initial attack of the snare drum")

As far as the overall design goes, it is always a balance of many parameters such as cost, physical chassis size considerations, total power, favored response and optimization of certain parameters driven by basic concepts of how various capacitors act in circuits.

One thing for sure, there have always been "legendary" amplifiers and they have always sounded "fast", "tight" and "in control". Eye flinching, rectum puckering dynamic transient response...Anyone who has been into audio for the past 3-4 decades is well aware of those "brands". Those brands were not shy about "Bigger is Better" adage...


Can you spot the eye flinching, rectum puckering capacitor bank in this amp? The man still builds them like he always used to.

By the way, the big capacitors do take some time to charge, it is not an instantaneous process and one can clearly see that in this video on the voltmeter. One can also appreciate the instantaneous discharge that is good enough to weld metal from a 1 KiloJoule @400V capacitor bank. Capacitor bank discharges. 12,500µF @ 400V - YouTube


How about kicking some aluminum cans around with a capacitor bank? Capacitor bank 11,3kJ 350V discharge test - Featured on Hacked Gadgets - YouTube

Mark Levinson legendary ML2 monoblocks. A 25w into 8 and 50w into 4 Class A amps. How much capacitance could it possibly need? Back in those days, nothing but the best would do. Sprague Nippon, very generous capacity capacitor bank.

Krell KSA-50S. Look at that "testicular fortitude" for a 50w amp Class A amp.

Solid-state stereo power amplifier. Specified output power: 50W into 8 ohms (17dBW), doubles with each halving of load impedance down to 1 ohm. Maximum output voltage: 75.8V peak to peak, 26.8V RMS. Maximum output current: 60A.

Just some of the capacitors in my preamp....and it doesn't need to be a big as a D'Ag amp.

Big caps bank vs small cap bank all are different and very dependent on output stage bias load demand. Regardless in every amplifier you are basically listen to the PSU, it is that important ..

Personal preference is large PSU main caps followed by multiple small caps of differing sizes ..

Regards

Larger caps are better behaved and more reliable than smaller ones. Issue is they cost more and they require a much larger overall case to fit. Most of the time a manufacturer is dealing with significant space limitations

Older amp designs used large caps because they were readily available at a reasonable price then. Now, modern industrial and commercial products use much smaller caps. These smaller caps use modern construction on newer machines. Their price per microfarad is lower and they are much more available.