Ultimate No-load Ungrounded Blend Pot (Pics!)

Discussion in 'Pickups & Electronics [BG]' started by walterw, Aug 13, 2014.

  1. walterw

    walterw Supportive Fender Commercial User

    Feb 20, 2009
    not sure what you mean

    that's the wiring diagram regardless of whether the traces are cut or not. in theory leaving the traces uncut causes a little bit of "leakage" from the other pickup, cutting them creates a definite "off" for the unselected pickup
  2. Ringhammer

    Ringhammer Supporting Member

    Sep 3, 2016
    S. F. Bay Area
    In the diagram, there is no wiring connected to the lugs that would have their traces cut. If nothing is connected to those lugs, isn’t the same as cutting the trace, since it’s only a fraction of an inch away from the open ended lug?
  3. Stephen Gagel

    Stephen Gagel

    Feb 27, 2020
    guitar-wiring-diagram-jpg.jpg I have been working on the issue of the blend being somewhat of an on of switch with a non-grounded blend. What I have been doing is using 100k m/n and 50k m/n pots. What I found was a 250k m/n pots have a very small blend area. I used some strat knobs with numbers on them and found that from center detent (which is 5.5) ether way (4.5 to 6.5) you were done blending and you were ether on one or the other pickup. So one number difference in ether direction is all you have to blend with. Lets say you have five numbers from center each way so 250k divided by five is 50k. So I found some 50k and 100k pots. I tried the 100k first and found that it gave me about 2.5 to 3 numbers worth of blend ether way from center and a positive solo at each end. I tried the 50k m/n and it gave me blend from one end to the other but not a good solo on ether end so I went back to the 100k m/n pot. Now the only 100k and 50k m/n pots I found or Alfa pots made for a circuit board and have prongs on them rather than solder terminals. So you just make a loop on the end of the wire, slide them on and solder. They also have a small shank diameter of .268" so I made some step down washers out of brass to adapt them to my 3/8 holes. Anyway I am using a 250k linear pot for Vol. a 100k m/n pot for Blend and a 250k audio with a DPDT switch on it for tone. The switch is for series / parallel and the entire system works wonderful.MN Taper - Rotary Potentiometer - Potentiometer / Variable Resistors (taydaelectronics.com)
  4. walterw

    walterw Supportive Fender Commercial User

    Feb 20, 2009
    no, it's very different with the trace cut
  5. Ringhammer

    Ringhammer Supporting Member

    Sep 3, 2016
    S. F. Bay Area

  6. Maybe this drawing will help.

    With one end of the pot disconnected, the pot is now a variable resistor (aka rheostat).

    Left drawing, without a no-load cut, shows a slight leakage signal thru the variable resistor to ground. Slightly diminished signal goes forward.

    Right drawing shows that, with a no-load cut in the proper spot, no leakage can happen. Full strength signal goes forward.

    NoLoad detail.png
    Papaschtroumpf, XLunacy and walterw like this.
  7. Ringhammer

    Ringhammer Supporting Member

    Sep 3, 2016
    S. F. Bay Area
    In the pics earlier in this thread, he is showing a cut on the trace to a lid that has nothing connected to it, including ground, so I don’t get how cutting a trace to a lug that is in effect left open (not connected to anything) has any effect at all. Your diagram shows a cut interrupting a path to a volume control. I must be missing something somewhere…
    fig likes this.
  8. No you aren't, this was my bad. I showed you a diagram for "full-on" from a different circuit. Same concept, though. I apologize for that.

    You want a "full-off", correct? Where the wiper arm is rotated to the disconnected ground terminal and no-load cut?

    If so, give me a few minutes to do a diagram.
  9. Ringhammer

    Ringhammer Supporting Member

    Sep 3, 2016
    S. F. Bay Area
    What I thought was that in my ungrounded V/B/T configuration, when I dialed all the way to the neck position it would be that pickup absolutely solo, as if the bridge pickup was not there at all. Not really concerned with having it that way for the bridge because I would likely never want to solo the bridge.

    Earlier in this thread there is a diagram of the ungrounded V/B/T for Jazz and I thought the unused lugs were the same ones he cut.
  10. NoLoad detail.png

    Since a blend pot is essentially two pots, one physically reversed from the other, this drawing represents only 1/2 of a blend pot. The very same "full-off" no-load cut near the ungrounded lug applies to the second half of the blend pot.

    Terminal 1 is where the ground would go. With the cut shown in the right-hand drawing, no leakage happens (no slightly hearing the 'off' pickup). Full solo function of the remaining 'on' pickup.

    I hope this helps. Again, my apologies for the earlier confusion.
    walterw, Papaschtroumpf and XLunacy like this.
  11. I know this is a fairly old thread, so I hope someone sees this and can explain something to me. I am wondering why a linear taper pot for the volume in this configuration? Most manufacturers seem to use an audio taper for the volume pot.
  12. bigtone23


    Dec 10, 2014
    Denver, CO
    Linear volumes are great for instruments that stay on the cleaner side of things downstream. You get a wider and finer range of adjustment, particularly on the top half of the pot's rotation. Audio taper is usually preferential for those that like distorted or crunchy tones, as the faster drop in value helps 'clean up' the tone with less rotation of the pot.
    For example, I like linear volumes on my basses and audio tapers on my guitars. I play mostly cleaner tones on bass and always crunchy tones on guitar. I like when my guitar volume rolls back to about 5 or 6 and my tone cleans up. On a typical, modern audio taper pot, 5 on the knob is about 10% of the pot's value. On a linear taper pot, 5 is 50% of the pot's value. To get to that same value for a clean tone, I have to roll a linear pot back to about 1-2. That's a wide sweep and a lot of rotation for someone that rides the volume control for cleans.

    The opposite is true, too. Lets say I have a clean tone and just need to drop my volume a touch. On a linear taper pot, dropping the volume to about 7 is a noticeable drop (which is also about 70% of the pot's value). The equivalent resistance on an audio taper pot is at about 8. However, on the audio taper, that drop doesn't have a forgiving wiggle room. Overshoot your desired setting (of 70% resistance) and drop to 7 on the audio taper and you are now at about 50% of the pot value and the volume really drops out. On a linear pot, dropping an extra number (to 6) is still only 60% of the value, which is not terribly lower.
    This is why VVT controls on newer basses are usually linear volumes with an audio tone. It just gives the player finer adjustment of those blends. Audio taper is still the preferred tone pot-linear tones are more like a on/off switch--all the action is from 2-0. I theorize that Fender used audio taper all around just to keep the parts orders smaller. Get a batch of solid shaft 250K audio for the Teles, Ps and Js, and a batch of 250K split shaft audios for the Strats.
    walterw, fig, bassically_eli and 2 others like this.
  13. Thanks Bigtone 23. So the world isn't going to end if I use a linear taper pot in my G&L SB-2 along with a blend pot? Here's another scenario. An SB-2 has just two volume controls; no tone. That's OK by me, except I like a master volume. A blend pot is one way to do this. I'm also looking at running a concentric stacked pot for individual volumes and run that signal to a master volume, but I don't know how to manage the resistance there or the tapers for that matter, so this blend pot idea might be the best. Thanks again.
  14. Ringhammer

    Ringhammer Supporting Member

    Sep 3, 2016
    S. F. Bay Area
    I would love to find a source for some solid shaft linear taper 250k and 500k CTS pots, with the short thread length for use on pick guard mounting. Anyone have that info. I usually get mine through “guitar parts factory”, but they never seem to have them.
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