Sunday, July 20, 2014

Capacitors: All Things are NOT Created Equal - Part 0

I have been struggling with how to go about this series since so much has already been written on the subject. I don't want to repeat what so many have contributed but I still find myself looking for someone to say it the way I would explain it with no results. So here it goes: a brief high-level explanation of the most commonly-used component in audio gear next to the transistor: the CAPACITOR.

Part 0 – Introduction

This series helps to demystify the claims manufacturer’s make about their extreme and justify the cost of their pricey capacitors. This series is a bit technical, focusing on more than just aesthetics, but the summary to this series will provide an insight to everyone explaining what works well and why.

It is true that capacitors sound “different” and there have been many subjective studies regarding this topic. Audiophiles and engineers argue back and forth about specifications and observed results with both sides quoting their own sets of tests confirming or disproving their particular position. (This is sort of like saying: I love standards because there are so many from which to choose.

But this series takes a slightly different approach where I believe that the assertions from subjective observations are true AND that the skepticism from engineers is also deserved.  Is this an oxymoron? Nope! Read on and see why.

When someone claims they observe something, in order for an engineer to accept that claim it must be reproducible and repeatable. The standard way in which such assertions is confirmed is through double-blind testing. But there is something that happens in the behavior of the results of a double-blind test when the results are repeated many, many times: the engineer assumes that the results will ALWAYS be the same as that of these undisputed samples. Is this true OR is the sample size just too small OR is the design of the double-blind test itself in some way flawed OR are the participants? Good questions and this reminds me of the Kodak-Nikon test.

Let me summarize this test briefly for those of you unfamiliar with it. A while back Kodak sponsored a test to see if someone could tell the difference between various 35mm cameras taking pictures using their film. The test was to see if someone could pick out the ones taken with a Nikon camera and lens. What sounded like a slam dunk readily revealing that the subjective evaluations of photographs is in itself flawed because of the biases of the observers turned up one interesting twist. While almost all of the major photo critics of the time failed the test as anticipated, one picked out the Nikon photograph 100% of the time. That's right, zero errors.

What does this mean regarding such tests? Even tests to prove people are biased can themselves be biased if the sample is too small. Just imagine what conclusions would have been reached if this one person had not succeeded? Moral: Tests must be constructed very carefully, moreso than most are.

This series takes a different slant: it is an objective study that uses these subjective preferences as a starting point, and focuses on how the design of a capacitor preferred by these subjective ratings may gain a sonic edge over another. This approach will hopefully point you to a manufacturing process (aka a manufacturer’s series or material composition or whatever) that will give you the sound you want, or at least close to it, without having to go through the evaluation process yourself. It will also demystify how a capacitor is made and the planning involved in making a really good one (as opposed to a quick-and-dirty one).

Before I begin, I wish to provide some links to the works of others in this field acknowledging their superb efforts in analyzing the sound various capacitors possesses and the consistent way in which they have subjectively described the sound between them. It is a massive undertaking to describe the sonic attributes of anything, much less take the time to understand the audible effects of swapping a single capacitor in an electronic circuit. However, some folks have done a superb job in such an effort. Unfortunately by the definition of the word “subjective” this does not mean you can correlate one person’s views or impressions with another. Although they both may arrive at the same conclusion that Brand X sounds better than Brand Y, the reasons for saying so will probably differ.

In my opinion, the best audio-grade signal-path capacitor review is by the Netherlands’ based Humble Homemade HiFi analyzing an amazing diversity of products and providing a uniform – although subjective – rating system.  The second purely subjective multi-part article was written by Jon L. of Enjoy the Music while less thorough brings up very valid points. The great Joseph Levey also ventured into the fray with his Great Capacitor Shootout recommending specific brands over others.

Another work of important note is that of Martin Collums who way back in 1985 did what it is that I am attempting to do now. He risked his reputation back then from the professional audio community (few people desire being labeled a heretic by their peers) daring to claim that capacitors sounded different. History tells us now that Martin was indeed not a heretic but a man of science way ahead of his time attempting to correlate subjective impressions with objective measurements. He believed similarly to my own philosophy: what someone hears, we should be able to measure. The trick is to find what or how to consistently measure the observation, something that can prove to be far more complicated, elusive, and uncommon.

In his 1985 conclusions, Collums identified the following measurements and values associated with a quality capacitor, the last two of which are unfortunately non-standard specifications:

  • Dielectric Absorption of less than 0.1% (the property of retaining an electrical charge)
  •  Higher voltage than the designed circuit minimum (e.g., use 200V rating or higher in a 50V circuit)
  •  Low Equivalent Series Resistance (the losses incurred by adding the capacitor to the signal path)
  •  Low inductance (the electrical property that restricts transient response and high-frequency extension)
  •  Low internal leakage (self-discharge rate NOT the same as the ESR)
  •  Low piezo (mechanical-resonance and microphonic) effects
  •  Low delay error (ability to instantaneously track an abrupt change or impulse)

As you can see, there is a lot that must be examined to grasp the characteristic behavior of the lowly capacitor. For you to understand what I will explain, you must learn a few fundamental things about electronics (don’t worry, I’ll keep this to a minimum and make it as painless as possible). For those of you allergic to math, no worries here either. And for all of you, if you read this faithfully, your knowledge of how capacitors work will be greatly enhanced far beyond Wikipedia or other similar online helpful aids. 

So in Part 1, I will go over the generic fundamentals of a capacitor – any capacitor. In other parts of this series I will describe how engineers have tweaked these basic concepts to give the high-end community a superior product. So hang on…you are in for the ride of your life. Above all, remember to listen with your ears, not your eyes.

Related articles:
The Vishay 1837 Review and Modification
Bypass Capacitors
Mundorf Supreme Capacitor Review - Part 1
Mundorf Supreme Capacitor Review - Part 2
Capacitors: All Things are NOT Created Equal - Part 0
Capacitors: All Things are NOT Created Equal - Part 1
Capacitors: All Things are NOT Created Equal - Part 2
Capacitors: All Things are NOT Created Equal - Part 3

Yours for higher fidelity,
Philip Rastocny

Skeptics are essential to keep us sane; skeptics do little to keep us inspired. Philip Rastocny, 7-16-2014

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