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  1. #1

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    I know this question has been discussed many times on various groups, but all the posts I see are about guitars designed for rock. I am going to put a floating Johnny-Smith type humbucker on an archtop. I want to have both volume and tone controls and I generally like a “dark” tone. Before ordering new pots, I checked out my parts drawer to see what I have lying around. I found a pair of mini pots that came off a similar setup back in time. I would have expected both pots to be 500k, but I notice that the volume pot is 500k and the tone pot is 250k. Can I use this combination? What would be the effect of mixing them like this? Should I still use the standard .022uF capacitor on the 250k pot? Any advice would be much appreciated.
    thanks,
    Keith

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  3. #2

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    Quote Originally Posted by floatingpickup
    I know this question has been discussed many times on various groups, but all the posts I see are about guitars designed for rock. I am going to put a floating Johnny-Smith type humbucker on an archtop. I want to have both volume and tone controls and I generally like a “dark” tone. Before ordering new pots, I checked out my parts drawer to see what I have lying around. I found a pair of mini pots that came off a similar setup back in time. I would have expected both pots to be 500k, but I notice that the volume pot is 500k and the tone pot is 250k. Can I use this combination? What would be the effect of mixing them like this? Should I still use the standard .022uF capacitor on the 250k pot? Any advice would be much appreciated.
    thanks,
    Keith
    If it sounds good to You, yes!

    My ES-175s are from 1984 and 2015. Both have (according to the Gibson Customer Service) 300 kOhm vol pots and 500 kOhm tone pots. Older has Shaw humbuckers and newer has P90s. Both sound great!

    The capacitor values have some thumb rules, ”Fender one coils this, himbuckers that”. The JS pickups surely have a rule too. They are cheap, You can easily buy ”the right one” and some others to experiment. I don’t remember the values but I was delighted what a smaller value cap sounded in my P90 Les Paul.

  4. #3

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    Now that I look a little closer, this set up was wired the other way around - 250k volume pot and 500k tone pot. I could unsolder things and switch them around if I need to. Or, I can just order a new set. These are nice clean vintage pots though, and it might be nice to use them.
    Keith

  5. #4

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    It's more work, but you can try different capacitor values as already suggested. They generally cost pennies, and the shipping cost is far higher than the price of the caps. I would tend to try whatever I had on hand and see if that worked. It's certainly possible to use different values for the pots, and it's not really difficult to switch them if needed. It's just a hassle to remove and replace them in an archtop. Buy or make a helping hand like Stew-Mac sells and it's not so much of a hassle. Doesn't eliminate it, just mitigates it somewhat.

    A re-read of the OP indicates that the pots will be going on the pickguard perhaps. That makes rewiring much easier.

  6. #5

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    Quote Originally Posted by sgosnell
    It's more work, but you can try different capacitor values as already suggested. They generally cost pennies, and the shipping cost is far higher than the price of the caps. I would tend to try whatever I had on hand and see if that worked. It's certainly possible to use different values for the pots, and it's not really difficult to switch them if needed. It's just a hassle to remove and replace them in an archtop. Buy or make a helping hand like Stew-Mac sells and it's not so much of a hassle. Doesn't eliminate it, just mitigates it somewhat.

    A re-read of the OP indicates that the pots will be going on the pickguard perhaps. That makes rewiring much easier.
    Yes, everything will go on the underside of the pickguard, which will be easy to deal with. I also found what looks like a Mallory capacitor in the parts drawer. I attached a picture. Is that ok to start with?
    Mixing pot values-0f50035e-981a-466c-88d5-32ad96a924b9-jpeg

  7. #6

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    Yes to all of the above. I don't have the skills to be able to predict what combination is going to work best, but I can say that Kent Armstrong advised me to use a 500K volume pot and a 250K tone pot with and .047 capacitor to darken up the sound of my PAF0 floater.

    Experimentation might be the name of the game. The 250K in the volume position might render things a little dull, but I guess you never know unless you try. The JS pickup is a little brighter than the PAF style, so it might be good with the 500K in the tone position with the .022 capacitor. If you decide that it's too dark, then all you would have to replace is the volume pot.

  8. #7

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    Quote Originally Posted by Cunamara
    Yes to all of the above. I don't have the skills to be able to predict what combination is going to work best, but I can say that Kent Armstrong advised me to use a 500K volume pot and a 250K tone pot with and .047 capacitor to darken up the sound of my PAF0 floater.

    Experimentation might be the name of the game. The 250K in the volume position might render things a little dull, but I guess you never know unless you try. The JS pickup is a little brighter than the PAF style, so it might be good with the 500K in the tone position with the .022 capacitor. If you decide that it's too dark, then all you would have to replace is the volume pot.
    Thanks so much for the detailed response. I’ll give it a try.
    Keith

  9. #8

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    Quote Originally Posted by floatingpickup
    Yes, everything will go on the underside of the pickguard, which will be easy to deal with. I also found what looks like a Mallory capacitor in the parts drawer. I attached a picture. Is that ok to start with?
    Mixing pot values-0f50035e-981a-466c-88d5-32ad96a924b9-jpeg
    A couple of years ago I purchased about half a dozen of Mallory 150 caps and installed them in two or three guitars (humbucker and P 90) and I like them quite good.

  10. #9

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    Caps are caps. They all do the same thing, and as long as they're in spec, it's not possible to tell one from another. That one should work. I prefer the smaller disk type, because they're smaller and easier to fit into small spaces, but otherwise it makes no difference. People rhapsodize about oil/paper, orange drop, etc, but the truth is that they all do exactly the same thing, and the type and brand are immaterial, as long as they are within spec.

  11. #10

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    Not only does the cap technology have no audible effect but also changing the value to .047 from .022 has no effect when the tone pot is at full. With tone at full, the two pots are effectively in parallel, damping the resonance between the pickup and the lead. Turning the tone pot down from 500k to 250k will increase the damping, darkening the tone a little, independently of the cap value. The tone needs to be turned down further before the cap value becomes significant. Ultimately, the pickup resonates with the cap to give a characteristic sound with a peak at a few hundred Hz. The .047 resonates half an octave lower than the .022.

    Turning down the volume a bit isolates the pickup from the cable capacitance, moving its resonant peak to a higher frequency where it will be inherently less audible. It also puts a low pass filter of part of the pot resistance with the cable capacitance into the circuit. These two effects together dull the sound slightly.

    The Johnny Smith (1967) uses .022 ceramic caps and 500k pots.

    https://www.gitec-forum-eng.de/wp-co...ntiometers.pdf

  12. #11

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    Quote Originally Posted by sgosnell
    Caps are caps. They all do the same thing, and as long as they're in spec, it's not possible to tell one from another. That one should work. I prefer the smaller disk type, because they're smaller and easier to fit into small spaces, but otherwise it makes no difference. People rhapsodize about oil/paper, orange drop, etc, but the truth is that they all do exactly the same thing, and the type and brand are immaterial, as long as they are within spec.
    I do agree and the fact that the Mallorys made a difference may be due to tighter tolerances in their specified value compared to ceramic discs they replaced...

  13. #12

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  14. #13

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    It's true that not all capacitors have their specified value. Nor do resistors, including potentiometers. Everything has some tolerance, and some devices have as much as 10% plus or minus. That's quite a bit, but such is the specification. You will not find any pots that are exactly 500k or 250k ohms, nor any other value, unless it's just by pure luck. But for the applications being considered here, they're almost all close enough.

  15. #14

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    Quote Originally Posted by sgosnell
    It's true that not all capacitors have their specified value. Nor do resistors, including potentiometers. Everything has some tolerance, and some devices have as much as 10% plus or minus. That's quite a bit, but such is the specification. You will not find any pots that are exactly 500k or 250k ohms, nor any other value, unless it's just by pure luck. But for the applications being considered here, they're almost all close enough.
    And the solder joints that secure and connect them can have far greater effect on tone than the caps and pots themselves. Heat can drastically change the value of a part or render it useless, so you need to use the right size iron and control the spread of heat. A poorly soldered joint can add capacitance, resistance / inductance, or some combination of them.

    Heat is one enemy of a good joint and a poor mechanical join is another. Make sure the parts to be soldered together have as tight a physical connection as possible after cleaning the mating surfaces thoroughly. If you can’t twist or otherwise secure them together (eg when soldering a resistor or cap lead or a wire to the body of a pot), clamp the lead to the pot with a hemostat or similar metal tool. I also clamp a small hemostat on each lead to serve as a heat sink.

    The joint has to be hot enough to melt the solder - do not melt it on the tip and wipe/drip it onto the joint. It has to flow freely onto and into the joint to be properly conductive. Too much can alter the RC parameters of the circuit, so only add enough for a thin and shiny joint. Let it cool thoroughly before touching anything, to avoid shifting the parts. If the joint looks hazy when cool, redo it.

  16. #15

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    My 2 cents. If you like a dark sound for jazz, what will really get you there is a 100k volume pot. 250k for volume is darker than 500k but it isn't really that dark in a jazz context. For the tones, I use 250k no load pots for everything. That way on 10 it is max bright, and then I will start to notice it get darker as soon as I pop it to 9 or 8. The top of the sweep of a 500k tone pot is all coloring and not really darkening until you get around the 250k range. About the caps, there's a difference in tone between cap materials that is audible. Saying caps function as only a result of their spec is circular reasoning and the same as saying the only parameter that affects the way a string sounds is its diameter.

  17. #16

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    Quote Originally Posted by Clint 55
    About the caps, there's a difference in tone between cap materials that is audible. Saying caps function as only a result of their spec is circular reasoning and the same as saying the only parameter that affects the way a string sounds is its diameter.
    There is nothing circular about the reasoning and that critique doesn't even make any sense.

    Think about how the capacitor functions in the guitar tone circuit. All of the signal that passes through it is bled off to ground. You never hear the signal that goes through the cap. As a result, the construction of the cap (ceramic, polymer, paper and oil, etc.) can't make any difference because none of that signal is ever heard.

    The capacitance value of the capacitor is all that determines which frequencies are bled off to ground. The accuracy of the specification may vary by construction, I don't know about that; +/- 20% seems to be about standard for capacitors but perhaps some construction designs have a narrower range than others, which would make the outcome more predictable. But you are still not able to "hear" the capacitor.

  18. #17

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    Different cap materials can still filter differently and result in different sounds even if they work by filtering highs to ground.

    Also, tone caps are only ever bypassed if it's a no load pot. They're still in the circuit and darken the sound even if the regular pot is on 10. Not so much with 500k but audible with 250k.
    Last edited by Clint 55; 07-20-2021 at 02:19 PM.

  19. #18

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    Quote Originally Posted by Clint 55
    there's a difference in tone between cap materials that is audible
    Yes there is. And the reasons are not mystical or mythical. Probably the most important element in a cap that can affect the tone of signals passing through it in a circuit is the dielectric, and this varies in composition, dimension etc from type to type and brand to brand. The variation in design, construction, and composition of caps definitely affects sound quality. Walt Jung and Richard Marsh have studied this intensively and attribute it in large part to the parameters of capacitor function known as dissipation factor (DF) and dielectric absorption (DA). For a deeper dive into this, see this 1980 article by them in Audio. To behonest, I've never found a meaningful difference when changing the type of caps in the control circuit of any guitar I've ever owned - I suspect the differences were mostly from altered capacitance rather than different types of capacitor. No cap change ever made a guitar sound significantly better or worse to me.

    There's also a great article on this by Bob Pease ("Capacitor Soakage") and a series by Cyril Batement ("Capacitor Sound"). Pease agrees that there's a difference, but he's skeptical that it's sufficient for very many people to hear it in audio circuitry. To my ears, the caps in the signal path are far more influential in audio equipment than in the pickup circuitry of a guitar, but the effects were definitely audible the few times I've done blinded comparisons myself in my own audio systems. For example, I upgraded all the caps in my Marantz 7c many years ago and was able to ID mine consistently next to a stock one that tested to the same specs in the same system at my dealer's shop, when his tech tested us and a few other customers. My dealer and most of the customers also called it correctly each time. Yes, mine sounded better - cleaner, more open, and with greater detail across the spectrum (but better as frequency went up, as you'd expect).

  20. #19

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    I notice meaningful differences.

  21. #20

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    Thanks for the helpful information that all of you provided. I ended up using a matched pair of pots after all, and the result was very satisfying. I saved the other 500/250 combination to use on the next installation. I have learned a lot from this thread. Thank you!
    Keith

  22. #21

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    Herbie:
    "My ES-175s are from 1984 and 2015. Both have (according to the Gibson Customer Service) 300 kOhm vol pots and 500 kOhm tone pots."

    What hogwash. Don't believe what you hear.

    My '81 L5CES and my 2001 57 RI LP both had pots that ranged from 90K to 310K. And some of them stopped working. What kind of QC is that?

  23. #22

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    Pots have a nominal value ( 500k, 250k, etc) but the actual value is variable. Most have a 10% tolerance, and not all meet the tolerance spec. They're generally the least reliable (for accuracy) element in a system. Mostly because high accuracy isn't necessary for them to work satisfactorily.

  24. #23

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    Great, and we all know that, but it doesn't help when we are trying to maximize the tone of a guitar. When I have to turn the Treble control on my Fender amp to 8 to get a nice tone out of a guitar, (and even then, it still isn't speaking to me) it's time to do some "under the hood" inspection.

  25. #24

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    Note that the frequency response of a 250K tone pot set to 10 is identical to a 500K tone pot turned to half resistance. If it’s an audio pot, half resistance won’t be at half rotation. If you have no need for the upper (brighter) half of the range of a 500K tone pot, you may be happier with a 250K pot, as it will have a more gradual tonal effect as you roll it down.

    The capacitance value and the resistance of the volume pot have a much more complex effect on tone, as they both interact with the impedance of the pickup. Selecting those values is mostly a matter of experience or trial and error, but there are frequency response calculations on the internet that can help guide which direction to go if you are trying to tailor your pickup’s response.

    This might be moot since you’ve already decided you’re happy with your values, but I thought it was worth mentioning.

  26. #25

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    Quote Originally Posted by KirkP
    Note that the frequency response of a 250K tone pot set to 10 is identical to a 500K tone pot turned to half resistance. If it’s an audio pot, half resistance won’t be at half rotation. If you have no need for the upper (brighter) half of the range of a 500K tone pot, you may be happier with a 250K pot, as it will have a more gradual tonal effect as you roll it down.

    The capacitance value and the resistance of the volume pot have a much more complex effect on tone, as they both interact with the impedance of the pickup. Selecting those values is mostly a matter of experience or trial and error, but there are frequency response calculations on the internet that can help guide which direction to go if you are trying to tailor your pickup’s response.

    This might be moot since you’ve already decided you’re happy with your values, but I thought it was worth mentioning.
    That's very interesting. I will be doing another project soon, so this will be very helpful.
    Thanks,
    Keith