Re: Capacitor value?
Nice post, other than it being 100% completely inaccurate on every single point.
My advice is actually try it before you post on something you don't understand, and you might also do some research on the actual frequencies that get rollled off.
.0022uf on a humbucker has a very pronounced effect. It takes a solid body and makes it sound like a good L5. The tone is VERY useful in a band situation as it mellows the tone out BUT DOES NOT KILL THE MIX CUTTING ABILITY OF THE INSTRUMENT like .047uf or .022uf.
The other thing you don't know is that pickups in parallel respond differently than single pickups, and that single coils respond different to a tone cap than a humbucker. In general, to get the same roll off, you need double the size cap to get the same aural affect on pickups in parallel than on a single pickup, and double the size cap on single coils as humbuckers.
Thats why on humbucker guitars I often put in a push/pull with a .0022uf and a .0047uf, or on singles a .0047uf and .01uf or .0033uf and .0056uf.
So why don't you actually try it and listen to it before spouting off. I've done that mod on more guitars than I can even count, I have yet to have anyone tell me they couldn't hear it or didn't think it was an improvement.
Well, when you consider that pretty much every stock guitar on Earth has either a .022 or (shock! horror!) .047 tone cap in it, your "amp buried in the back yard" comment is ... a wee bit of an exaggeration maybe?
Also, keep in mind we're talking about a tone
pot, i.e. it has a large range of effectiveness over the rotation of the pot. You can roll the pot all the way down for a big cut (a very useful smooth, jazzy tone actually), turn it down to 9 to shave off a bit of highs and high mids, or anything in between. It's not like we're talking about an all-or-nothing switch here.
Really, it just comes down to what your goal is with a tone pot. If you want to be able to take a bigger bite out of the treble and high mids, use a .022 or even a .047. If you want to roll off treble only, that's a .010. Anything lower than .010 is going to only be effective on the high treble band. That's completely fine if that's what you want from your tone control, but don't pretend it's anything other than a high treble/presence cut.
As for the actual frequencies that get rolled off, I'm sure a smart guy like you knows how to calculate the corner frequency of a first order passive low-pass filter, right? Of course you do. But for the benefit of everyone else, here's the formula:
fc = corner frequency (the highest frequency the filter lets through)
R = series impedance load, in Ohms
C = capacitor value, in
Farads
In the case of a guitar's tone pot, the series impedance load is the impedance of the pickups themselves, therefore the results of this equation will vary depending on your pickups. For the sake of argument, let's try this out with a '59 bridge, which is 6.8k.
For a .047 uF (47 nF) cap:
fc = 1 / (2 * pi * 6800 * 47 * 10^-9) = 497 Hz
For a .022 uF (22 nF) cap:
fc = 1 / (2 * pi * 6800 * 22 * 10^-9) = 1063 Hz
For a .010 uF (10 nF) cap:
fc = 1 / (2 * pi * 6800 * 10 * 10^-9) = 2341 Hz
For a .0047 uF (4.7 nF) cap:
fc = 1 / (2 * pi * 6800 * 4.7 * 10^-9) = 4980 Hz
For a .0022 uF (2.2 nF) cap:
fc = 1 / (2 * pi * 6800 * 2.2 * 10^-9) = 10638 Hz
A hotter pickup will lower the corner frequency, of course, but as you can see those really low value caps are only shaving off the highs. The .0022 is basically a presence control, in fact.
Final note: the cut-off at the corner frequency is more of a slope than a hard chop. There is no such thing as an "ideal" low-pass filter in the real world, so keep in mind that even at zero, your tone pot is letting through plenty of frequencies above the corner.
Like I said, if that's what you want from a tone pot, that's totally fine, but don't make like anyone who chooses otherwise is an idiot.