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Thread: New electric build, tone pot volume problem

  1. #1
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    Default New electric build, tone pot volume problem

    Thought I'd post here instead of builders section as that is often very acoustic based - but please let me know if you think that would be more appropriate.
    I've just completed my first electric build but think I've got some wiring wrong. When I turn the tone pot to zero the volume also drops to zero. This happens at the very end of the range, so no volume affect all the way to 1, then a sudden drop to zero at tone zero. Is that normal? I don't remember this from electric guitar playing days. Maybe related is that the tone pot isn't very effective until close to zero either, but I reckoned that might be too high a value (0.47) and will try a lower one. The volume pot works as expected.
    The wiring is a pbass pup split into two and then wired following the standard stewmac 2 single coils diagram. Poor quality pic of the insrument below, I could post pics of the cavity wiring but not sure that would help - just looks like lots of wires!
    Any ideas before I change the cap?
    Tony.
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  2. #2
    Registered User Tom Wright's Avatar
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    Default Re: New electric build, tone pot volume problem

    It's easy to make wiring errors (I have made plenty). .047 works fine for me. The thing is to take a wire from where the pickup wire goes into the volume pot and send it also to the tone pot. That will short to ground when the pot is turned the appropriate direction. It doesn't matter if you go "in" the wiper (center lug) or the side lug, but don't mix up where the capacitor wire goes. I think you are grounding out at first, maybe you connected the shunt wire to ground instead of the wiper.

    Here's the basic wiring, with inputs going in at the center lug and out through one side:

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    Registered User Tavy's Avatar
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    Default Re: New electric build, tone pot volume problem

    You definitely got something wrong, Tom's diagram is slightly different to how I do it, but the effect is the same. Basically, the cap goes between the outer lug and ground. And the both input and output line level goes to the middle lug. I use the opposite outer lug to Tom so that clockwise pot-knob-turn gives you "full open" with no cut.

    BTW .047 is way too large for a mandolin and will cut out almost all the frequencies, fine for an octave though, not sure which yours is, but for mandolin I would go for something more like a .010. Try some different ones and let your ears be the judge...

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    Default Re: New electric build, tone pot volume problem

    Thanks for the replies both.
    Yes, I've not got either of those methods. And quite a bit different from Toms diagram. If looking at the back my hot comes from volume right lug to tone left lug. Then my cap is linked between tone centre (wiper?) to ground. If I've understood right i think i need to link my cap back to centre vol, which is also my hot to jack. I need to have a look at that diagram again.
    It's a mandolin, gdae, I like the cutting tone it has at the moment, but yes I'll likely try a lower cap too. Thanks for your help, I'll let you know how I get on.

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    Default Re: New electric build, tone pot volume problem

    I've now got hot to middle tone lug and cap between left lug and ground. The cap has been reduced to. 22. It's improved the way the treble is cut - but it's still got the same effect to no, or very, very low volume when the tone is turned to zero. I can't see where I might have gone wrong. looks like I'd be best disconnecting and then start from scratch again. All good experience I guess.

  6. #6

    Default Re: New electric build, tone pot volume problem

    Audio vs linear pot-Choosing audio (log) vs. linear depends on what you will be using the pot for. You should always use audio pots for volume control, otherwise you will find that the volume does not change smoothly as you turn the pot up and down. With a linear taper pot, you will find that the volume increases slowly from 0 to about 60 or 70 percent, then increases rapidly from that point on. This is because there isn't a direct relationship between resistance and volume in a passive circuit (which is what a guitar with passive pickups is). Audio taper pots compensate for this, and give you a consistent volume change throughout the sweep.

    A tone control, on the other hand, works best with a linear taper pot. The role of a tone control is to feed part of your signal to a capacitor that bleeds the treble to ground. In order to have a smooth transition from bright tone to mellow tone, the pot has to be linear. You can use an audio taper pot in a tone control, but you won't find the tone roll-off to be as smooth as it could be.

    Regarding capacitors: a guitar's tone circuit is what is known as a passive low pass filter. The capacitor only lets high frequencies through, and it dumps these frequencies to ground. Whatever is left (low frequencies) continues on to the volume control and out the jack to the amp. This is why it's called a low pass, because the lows "pass" through the circuit while the highs are blocked.
    The value of the cap determines at what point in the frequency spectrum the frequency cut-off occurs. The higher the cap value, the lower the cut-off point will be. In other words, higher value caps will make your tone darker when the tone control is set below 10. Strats and Teles generally have .022 uF caps and Les Pauls generally have .047 uF caps. I have seen guitars with caps as high as .068 and as low as .010. Source Seymour Duncan

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    Registered User Tom Wright's Avatar
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    Default Re: New electric build, tone pot volume problem

    We're getting confused, perhaps, because you can do this two ways, but the principle is the same for either. The pot is a variable resistor, and you insert it between the pickup and the output. The ground side goes to ground everywhere. The hot side goes into either the outer lug or the center one (wiper). The function of the capacitor is that it passes high frequencies, which are shorted to ground when tone is turned down.

    The tone pot should have a bridging, or shunt, wire come directly from the hot side, not after the volume, but parallel to it. That is, bridge from where you first attach the pickup to the volume pot. So if you come in the outer lug, the tone shunt wire comes from that lug, not the center. Vice versa, if you bring the pickup wire to the center lug, the tone wire comes from that lug also.

    An .047 does take a lot of the highest notes, which is why I tilt my pickups to balance away from the bass. I use the whole tone range, usually rolled off some. Then again, I'm accommodating a C string.
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    Default Re: New electric build, tone pot volume problem

    Thistle - my pots were one of each and the audio was fitted in the volume position. There's always a chance I mixed them up, but I don't think it's a pot mix up problem.
    My wiring is the same as this image for a tele. Thanks again Tom for your explanation and I think I understand the difference to your diagram, but with the same effect. I'm now wondering if i have a dodgy tone pot, maybe shorting everything out at zero. Anyways I'm going to start afresh, check for bad joints etc.

    edit:realised the image was prohibited to reproduce so here is link instead http://guitarelectronics.com/tele-st...iring-diagram/
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    Registered User Tavy's Avatar
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    Default Re: New electric build, tone pot volume problem

    Quote Originally Posted by Hewines View Post
    Thistle - my pots were one of each and the audio was fitted in the volume position. There's always a chance I mixed them up, but I don't think it's a pot mix up problem.
    My wiring is the same as this image for a tele. Thanks again Tom for your explanation and I think I understand the difference to your diagram, but with the same effect. I'm now wondering if i have a dodgy tone pot, maybe shorting everything out at zero.
    Actually you want zero resistance in the tone pot when it's turned to full cut - that's perfectly normal - what's not normal is seeing a big difference between pot at "nearly zero" and zero if you see what I mean. Stick a multi-meter on it and check the resistance between ground and hot stays the same regardless of tone pot position: it should do as the cap only lets AC through. If not then either you have a short somewhere - something touching something it shouldn't (easy to do) - or you heated the cap up too much when soldering and it's shorting inside (been there done that too.... you can get get bad caps too).

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    Default Re: New electric build, tone pot volume problem

    Fixed it. And the problem was.... my capacitors were rated nano-farads, not micro-farads. Same numbers, 47,22 etc but different by a factor of 1000. The markings on caps weren't clear as to that, and I only figured it out when ordering more thinking I'd burnt them out. I can't really explain why that gave a volume drop but perhaps it was more how my ear perceived an all or nothing (I think) tone bleed on the nano caps.
    Thanks all for your help and info, all really useful. I'm pretty happy with the sound now - well, nearly. An Amuse pickup is on my Xmas gift list to sort the weak e string!

  12. #11
    Registered User Tavy's Avatar
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    Default Re: New electric build, tone pot volume problem

    LOL, well out by a factor of 1000 could be an issue for sure

    Congrats on getting it sorted!

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    Créateur des e-mandos Soundfarmer Pete's Avatar
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    Default Re: New electric build, tone pot volume problem

    Quote Originally Posted by thistle3585 View Post
    Audio vs linear pot-Choosing audio (log) vs. linear depends on what you will be using the pot for. You should always use audio pots for volume control, otherwise you will find that the volume does not change smoothly as you turn the pot up and down. With a linear taper pot, you will find that the volume increases slowly from 0 to about 60 or 70 percent, then increases rapidly from that point on. This is because there isn't a direct relationship between resistance and volume in a passive circuit (which is what a guitar with passive pickups is). Audio taper pots compensate for this, and give you a consistent volume change throughout the sweep.
    Ahhhhh the old A vs. B for volume ......... I know mandolins are a little different .....but.....Funny how just about every guitar company uses linear for volume and audio of tone ...... Fenders tend to use As for both tone and volume hence the quick roll off that some Strat players like so they can cut/swell with their pinky but I think this was probably done to keep things simple. Every Gibbo I`ve checked diagrams for use B pots for volume except the Explorer

  14. #13

    Default Re: New electric build, tone pot volume problem

    It's a grounding problem. When you turn the pot all the way it grounds the signal causing it to go dead.

    The best way to fix that is to do what's called a "star ground." That entails taking everything that should go to ground to a common ground point - usually a metal washer. Google is your friend.

    Do not solder grounds to potentiometer casings, that's the best way to cause problems like ground loops (heard as hum). If the pot case has to be grounded, run a separate wire from it to the common ground point.

    You end up with a big blob of ground wires that you wrap in electrical tape. It ain't pretty but it does wonders to clean up you electrical signal.
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