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Thread: Resistor Question

  1. #1
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    Resistor Question

    I added the two resistors shown in the diagram to a Clapton Mid boost pot in order to lower the gain. This is what was used in the powerhouse strat. I am happy with the reduction in gain but it also seems to have brightened up the sound way too much for my liking. Are both of these resistors necessary to reduce the gain or is one of them doing something with the tone? If so I could remove it. Thanks. (I have attached a schematic from Fender)
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    Last edited by gtto; 03-03-2017 at 03:28 AM.

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    Are you referring to items 19 and 20? Without breaking out the photos into an actual schematic, its impossible to accurately analyze unless someone here has done the same mod. But as a general rule you have to understand that any change to the resistances and/or pots in guitar pickup wiring is going to change both the signal level and the tone. The only exception is when the pickup signals are buffered by active electronics, which I'm sure you don't have unless there's a battery hidden in that guitar somewhere. And you also have to realize that the human ear doesn't have the same response at all volume levels, so that even if there were no actual change in tone, it could sound brighter at a lower level.
    Last edited by PeterPan; 03-03-2017 at 03:38 AM.
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    Yes. 19 and 20. Actually there is a 9 volt battery powering the whole thing. As for the ears and volume, the volume ultimately is the same. I wanted to lower the gain not to lower the overall volume but to make the boosted signal and non boosted closer in volume. Before adding the resistors the difference was way too much. Now even the non boosted signal is much brighter. I can compensate to some degree on the amp but I still prefer the tonality before the resistors were added. I am not sure what photos you are referring to. I attached a schematic not photos.

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    Member PeterPan's Avatar
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    What I meant was, its not a complete diagram, in the sense that there is no way to know what goes on inside the PC boards (Item 11 or 22). If the wires going into the POT (item 14) are coming directly from pickups, then the added resistance will change the tone, because it would change the load on those pickups. If it decreased the load, it would cause the tone to be brighter, because it would shift the pickup self resonance up to a higher frequency. On the other hand if that POT is wired to an active circuit that is capacitively coupled, the opposite might be true... increasing the load could take away some of the lows, which will sound brighter.

    Again I'm just stating possibilities, because its not possible to analyze the circuit (the PC boards are essentially "black boxes"). If the resistors are indeed causing increased highs, it may be possible to add some capacitors to cancel the effect. If they are not really adding highs, but are removing lows, then those resistors are probably not the best approach to dropping the gain without side effects. I'm sure what you want to accomplish is possible, but you may need more complete diagrams to nail down a solution. Otherwise, its a guessing game unfortunately.

    Perhaps someone else on the forum will have a better working knowledge of these PC board(s)
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    Take your pick.

    ericclaptonmidboost-1.jpg

    ec_midbst_user.gif
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    Peter,
    OK. I understand. Thanks for the reply. I see that someone posted the schematics. I was hoping that there might be an easy way to get the tone less bright butI can live with the treble if I have to. G

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    Quote Originally Posted by gtto View Post
    I was hoping that there might be an easy way to get the tone less bright
    Try disconnecting one end of Ref.#20 (24k). The mid boosted signal will still be attenuated by Ref.#19
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    Dave,
    Thanks. I will try that. g

  9. #9
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    If I were you, now having a complete schematic of the PC boards, I would print out a copy and draw in all the other guitar components using schematic symbols and labels. That way you have a complete "all inclusive" reference on a single page. From that, mods for what you're looking to accomplish now and in the future will be a lot easier to devise, and it won't be such a guessing game. Not "preaching" here! Having made mods to every guitar, pedal, or piece of music equipment I've ever owned, I've learned the hard way how easy it is to forget exactly what the hell I did, and then I end up wasting hours tracing out and drawing the complete diagram I should have made. :-)

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