Tone Caps, Bright Caps, Input Impedance & Other Nerding With Simon Jarrett – That Pedal Show

I came across this very interesting video:



So, I rambled on Mylespaul, as I often do:


“I love a lot of this, especially how amazingly beautiful this dude’s playing is, how clear he explains stuff, and the passion he has for all of it. I would sit and drink an entire bar with this guy if I had the chance.

That said, I gotta be an asshole and point out some stuff that needs an immense grain of salt here.

Some concepts are way off and should not be taken at face value, which is a shame really because the guy obviously knows quite well what he’s talking about. I mean his explanation of resonance and peak shift is not only spot on, it’s actually even better than the way many of my teachers ever explained it, and I’m talking about engineers, so you gotta respect that from a guy trying to boil down a complicated concept for a wide YouTube audience in just a few minutes.

However, several things are off here:

Asymmetric distortion and compression are being mixed up from the get go.

There is distortion happening due to the saturation of the tubes, regardless of symmetry, which results in compression and because of that, added harmonic content comes into play, i.e. harmonic distortion. This happens even when the sound doesn’t seem distorted at all.

Compression, which is also mentioned, is a consequence of the tubes getting saturated, and in this case is a direct consequence of distortion itself. The way it’s mentioned is confusing and inaccurate as well.

These phenomena are equally true for both asymmetric and symmetric types of distortion. What differs between both scenarios is the proportion of even and odd harmonics being created. Odd harmonics become less and less musically correlated to the first harmonic as you go down the harmonic series, while even ones do not, which is why even ones are generally favored by many. The way this is explained mixes up the concepts and makes no sense.

All of the above is probably why Mick never heard it explained that way, it’s so wrong it hurts.

Then the rolling of highs to ground by the tone control, that’s not how that works, nothing gets “rolled off” to ground. What you do by turning the tone knob is “blending in” the value of the tone cap to the rest of the capacitance present on the circuit, shifting the entire transfer function to a lower, different resonant peak, as if you added a different cable with a huge capacitance. There is however, no actual rolling of the highs to anywhere, but a change in how the source creates the signal. It might seem like the same thing, but it’s not.

This is a frequent mix-up because we look at the tone control as a low pass filter. It is not. It’s more like a Zobel network, a completely different beast.

And while I love that he points out that cap type doesn’t matter, it’s a shame he does it for the wrong reasons. Again, ignoring the fact that “going to ground” is not correct here, the components that are subtracted from the signal are just as important as the ones that remain (like the light that’s absorbed by a material is just as important as the one that’s reflected to make you see a particular hue of color), so attention to the way the signal is subtracted is key, not something to be thought of as a drain of shit to be discarded in whatever way. Regardless, I agree (well, physics agree), capacitor type is irrelevant here.

Now, one thing everyone should indeed go listen to is beginning at 44:56. Ignore the “bleed to ground” thing, again, but pay attention to the detail about series resistance he mentions on the volume pot, and how he points out that the higher it is, the more is causes treble loss when the volume is rolled down.

That’s the reason why I keep saying 500k pots are a big offender on the frequent cases of guitars going dark on low volumes, and why 300k pots are often better in this regard. Yet, higher value pots are always suggested as a fix for this very issue, when they actually make things worse.

I doubt anyone will get this far, and again, I know I’m being the asshole but all I wanna do is help where I believe I can. Besides, it says “Nerding” on the title, so as far as I’m concerned, I was invited to chime in.

TL;DR: Dude plays great and obviously knows a big deal about this, but some stuff is way off.”

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