We have all seen the marketing. We all know the hype. What’s worse is that we should all know better.
I’m talking about the magic mojo of the carbon composition resistor. For years and years there has been a growing belief that the use of carbon comp resistors can somehow transform a lifeless, poor sounding circuit or effect into tone-breathing machine of which legends and tales will forever be told! There are many ways to go on from here. What I would like to do is cover two things; how or why this myth has taken root, and whether or not there is ANY truth or proof in it.
Before I go on, I should point out that I am speaking specifically of carbon comps being used in low power effects (under 30V or so). This pretty much includes everything on your pedalboard.
In order to truly understand this subject, we should uncover the roots of the belief. There are varying thoughts on this, but the one that makes the most sense to me is our obsession with the tones of the past. When researching guitar effects, how many times have we seen marketing lines like, ‘VINTAGE (insert trendy amp name here) tones!’ Better yet, which of us have not Googled the same things while trying to narrow our search for the next pedal that will make us sound more like SRV, David Gilmour, etc. ‘Forget practice,’ we think, ‘there must be a pedal for that.’ *author’s note, build a pedal that actually DOES make you a better player.
Ok, back on topic. The point is that we often are in search of the gear that is going to make us sound like our heroes of old. Somewhere along the line, some genius actually thought, ‘Well, if everyone wants to buy gear that sounds old, why don’t I just build my new gear with the same parts as the old stuff?’ BOOM. The carbon comp resistor myth was birthed. Before we knew it we were bombarded with promises of NOS (new old stock) carbon comp resistors freeing us from our previously dull and boring tone, because obviously ‘they just don’t make them like they used to.’ And to be honest, it actually kind of makes logical sense, but does it make scientific sense? The answer is sort of yes and no.
So, we have uncovered a logical explanation to why and how the carbon comp craze was born, but the bigger, more important question is whether there is any truth in it, and if so how do we prove it? Much of what I cover in this next section will be referencing an article written by R.G. Keen. If you have read any of my previous posts you will probably recognize this name. I often reference his writing because he knows what he is talking about, much more than I. In his article here he talks about carbon comp resistors and there use in guitar amplifiers. After researching carbon comp manufacturer’s info there are a few things that pop up over and over.
1. Carbon comp resistors have excess noise (compared to metal film resistors)
2. Carbon comp resistors have a higher variability (a 100K CC resistor may actually measure anywhere from 90K to 100K)
3. Carbon comp resistors have high drift
So, I guess it is true, they don’t make them like they used to… they make them MUCH better than they used to.
All these shortcomings aside, however, there is one distinguishing characteristic that may just give this myth some legs. Carbon comp resistor have a high voltage coefficient of resistance. This basically means that the resistance of a carbon comp will actually vary depending on the amount of voltage applied to it! Because of this, a phenomenon called ‘resistor distortion’ can become present. This distortion is typically only in the 2nd harmonic and not enough to be HEARD as distortion, just enough to add a bit of love. And THIS, we love. So there you have it, proof that carbon comp resistors sound better than metal film!
Not so fast. As we look closer at this resistor distortion we find that it is only produced when two variables exist.
1) there must be a high voltage applied, around 100V and higher
2) there must be a large signal swings across the resistor
So I ask you, does this sound like the parameters that your 9V powered Tube Screamer functions within? No, not at all. And oh, how the plot thickens! Essentially what has happened is we have let our love for the days (and tones) of old, coupled with a half-baked-half-truth steer us into believing these pedal builders when they claim that what REALLY sets them apart is their use of NOS carbon comp resistors. What I wonder is whether they actually know that it is false marketing. Unfortunately, there will always be the man with the Golden Ears claiming that he can hear the difference, leading the masses like the Pied Piper of tone and thus reinforcing this marketing myth.
For more in depth info, I encourage you to read the full article by Mr. Keen.