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Thread: "Greasebucket" tone control mods

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    Member Emeritus Forever Steve A.'s Avatar
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    "Greasebucket" tone control mods

    Facebook 11/28/2014: "I just ran across a tone control circuit which looks very interesting. With the tone control maxed its like having a .02uf tone cap; with the control set to zero it's like having a .015uf cap (for the EC woman tone.) If you reverse the two caps it would go from .05uf to .015uf, more appropriate for a tele or strat. By changing the values you can get different high and low tone cap values. For example if both caps were .047uf, the values would go from .047uf down to ~,024uf. Without trying it out I don't know if it would work better with a linear or audio taper tone pot. (In my analysis I have ignored the added resistor which Is is 4.7k which should not make much of a difference."

    The actual Fender "Greasebucket" circuit uses a .1uf and a .02uf cap.





    Some links about the circuit...



    Greasebucket Tone control | Telecaster Guitar Forum

    http://music-electronics-forum.com/t31603/

    Mod Garage: The Fender Greasebucket Tone Circuit

    Click image for larger version. 

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    Steve Ahola

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    I don't think that the tone cap value (assuming the normal range of values used) or type makes a noticeable difference when the tone control is set to max resistance (assuming a tone control in the normal value range).
    This is because the the main action of the tone control at max resistance is to add a little load on the pickup, thereby lowering the frequency, magnitude and Q of its main treble resonance a bit; the cap can be replaced by a short without changing that effect.
    It's an easy thing to test for yourself, ie just bodge up a switch to short the tone cap out. That would be the 22nF cap in this case, as the 0.1uF cap is already shorted out when the tone control is set to max resistance.

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    ToneOholic! big_teee's Avatar
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    Strange looking, and looks pretty exotic.
    Anyone try it?
    I sure wouldn't want to add all that stuff, if it didn't work?
    T

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    It's only Rock and Roll, but I like it!

    Terry

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    Member Emeritus Forever Steve A.'s Avatar
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    Quote Originally Posted by big_teee View Post
    Strange looking, and looks pretty exotic.
    Anyone try it?
    I sure wouldn't want to add all that stuff, if it didn't work?
    T
    Fender has been using it on their Highway One guitars and on some of their custom shop strats since 2005. Here is another drawing...



    Greasebucket tone circuit for guitar

    Quote Originally Posted by pdf64 View Post
    I don't think that the tone cap value (assuming the normal range of values used) or type makes a noticeable difference when the tone control is set to max resistance (assuming a tone control in the normal value range).
    Many people including myself would disagree with you on that. Because of the very low voltage generated by a guitar pickup I believe it to be very susceptible to the influence of the type and value of tone capacitor used with the typical 250k and 500k tone pots set to maximum resistance. Even though the results of RC computations might seem to suggest otherwise...

    I'll see if I can find some A/B testing to support my position.

    Steve Ahola

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    Senior Member Silvertone Jockey's Avatar
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    A variation on that is two tone controls with normal wiring in parallel each having a different value of cap on them. My favorite guitar is my Charvinez (late 80's Charvell body with an Ibanez neck) with tone wiring as described. The bottom tone with the smaller value cap is really useful

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    This guy has several videos where he compares components, they are very informative and BS free:
    https://www.youtube.com/watch?v=W8dp9clGe-I

    From what I understand the 4.7K resistor keep the tone control from going full mud at the bottom of the rotation. There is another way to wire a tone control courtesy of Bill Lawrence. A traditional tone control is a variable resistor in series with a capacitor, connected between the hot an the ground. The alternate way is to connect one end of the potentiometer to the hot and the other to the ground. The capacitor is connected between the wiper and the ground. I assume that the capacitor prevents the pot from loading the pickup at low frequencies in a traditional setup and this allows the pot to load all frequencies possibly cutting bass slightly. I may play around with this on my next rewiring.

    Here's a few links about the greasebucket:
    Mod Garage: The Fender Greasebucket Tone Circuit
    Bass Bench: Decoding Fender?s Greasebucket and TBX Circuits | Premier Guitar

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    Old Timer Leo_Gnardo's Avatar
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    Quote Originally Posted by Steve A. View Post
    Facebook 11/28/2014: "I just ran across a tone control circuit which looks very interesting. With the tone control maxed its like having a .02uf tone cap; with the control set to zero it's like having a .015uf cap (for the EC woman tone.) If you reverse the two caps it would go from .05uf to .015uf, more appropriate for a tele or strat. By changing the values you can get different high and low tone cap values. For example if both caps were .047uf, the values would go from .047uf down to ~,024uf. Without trying it out I don't know if it would work better with a linear or audio taper tone pot. (In my analysis I have ignored the added resistor which Is is 4.7k which should not make much of a difference."
    There was a time - late 80's - when some of the local guitarists insisted I change their tone caps over for 0.015 uF "because that's what EC has!" OK, I saw the sense. Who wants to fiddle with their tone control trying to find the sweet spot where it's almost all the way down? Having the 015 there kept just a pinch of brightness, you just whipped the tone all the way down and there you are. Looks like this slightly fancy circuit pretty well accomplishes the same thing, and that 4K7 in series with the "tail" cap to ground simply imitates the effect of not having tone control all the way down, big deal.

    As for tone cap value altering guitar tone with tone control full up, it's a discussion with a long beard on it. One day I tried to hear the difference between several tone control conditions: 250K vs 500K control, .022 vs .047 uF cap, TC in circuit & out of circuit. I thought I did hear a tiny almost undistinguishable difference between these sets of conditions but nothing that would be a deal breaker either way. Then again it was no double blind test; of course my perception may have depended on thinking "I'm supposed to hear a difference." It would be delightful to hear from anyone who does a DBT test on this effect especially with multiple listeners. At this point AFAIC it's a "do you believe in flying saucers" subject.

    By the way I stocked up on 015 caps but the trend quickly fizzled and nearly 30 years later still have a bunch of them. <:0/

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