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Thread: Wiring up a blend pot

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    Wiring up a blend pot

    I'm wiring a 2-humbucker guitar with a volume, tone and blend (or pan) pot, with the blend pot taking the place of the normal 3-position switch. I bought a pan pot from Stewart MacDonald, 500K.
    Here's a link to the wiring diagram from the Stew-Mac site:

    blend pot
    In practice, both pickups sound muddy and dull. Looking at the diagram, it seems to me that I now have two 500K pots in parallel (the pan pot and the volume pot), in essence giving me 250K to ground. This would be like putting a 250K volume pot in a Les Paul. Am I reading this wrong, or is there a better way to wire this up?

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    Neal,
    Blend pots suck, maybe you can locate a 1meg blend. 3 way switches exist for a reason.

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    Quote Originally Posted by David King View Post
    Neal,
    Blend pots suck, maybe you can locate a 1meg blend. 3 way switches exist for a reason.
    Thanks, Dave. I'll keep experimenting...
    I've always loved the in-between tones that Les Paul players get by adjusting volumes, but I'm a single-volume-control type guy, and I'm old and set in my ways. When I need to turn up for a fill or solo, I want to grab 1 knob and be done. I thought the Vol/Tone/Blend configuration sounded ideal, but now I see why it's not done more often.
    I've seen 1Meg volume pots, but not 1Meg blend pots. I'll keep looking.

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    Neal, Custom pots might be an option, you could check with MEC in Germany.
    M.E.C. Pickups
    They can do various stacks and a 500k stack might be a good compromise for you.

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    Neal, you are right, Stew-Mac is wrong. Disconnect the grounds on the blend pot and your tone should improve. I use a blend pot on my RWRP ASAT, and some of the best tones are off center.

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    Quote Originally Posted by Glass Snuff View Post
    Neal, you are right, Stew-Mac is wrong. Disconnect the grounds on the blend pot and your tone should improve. I use a blend pot on my RWRP ASAT, and some of the best tones are off center.
    Thanks for the replies, guys. I tried disconnecting the ground to the blend pot, and the result was at the extreme rotation of the blend pot, the other pickup was still on a little. It never grounded out completely. Not a deal-breaker, but not how I envisioned it to work, either.

    Just for fun, last night I wired in a 1 Meg volume pot, and wired a 500K resistor between the blend pot and ground. The tone is back, but again, neither pickup shuts off completely.

    I'm really liking this control scheme... lots of tones with very few knobs.

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    Ooops! Sorry, should have mentioned that. I concocted a scheme to switch out the other pickup by rebuildng a toggle with the blades reversed so it was off - on - off, but that meant foregoing the tone knob. As I really like the "woman tone" thing, I found in the long run I could live without the sound of the "pure" pickups.

    I keep thinking about using a stacked pot for both tone and volume, but as you say, there's a beauty to simplicity.

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    Quote Originally Posted by Neal View Post
    Thanks for the replies, guys. I tried disconnecting the ground to the blend pot, and the result was at the extreme rotation of the blend pot, the other pickup was still on a little. It never grounded out completely. Not a deal-breaker, but not how I envisioned it to work, either.

    Just for fun, last night I wired in a 1 Meg volume pot, and wired a 500K resistor between the blend pot and ground. The tone is back, but again, neither pickup shuts off completely.

    I'm really liking this control scheme... lots of tones with very few knobs.
    Close, but not quite enough. I just was wiring up a blend pot and realized this was going to be a problem while drawing the schematic. Your problem is not having 2 paths to ground. Your problem is having three paths to ground, one from the volume, one from the tone, and one from the blend pot (in the Stew-Mac schematic, it is illustrated as a direct connection from the blend to the tone ground, but you can redraw the schematic with ground directly off the blend pot). In that case, you only get a 166k resistance to ground, and your signal is going to cut out badly. Lifting the blend pot with a 500k resistor and using a 1M volume is going to get your tone back, but it isn't going to allow you to blend out either pickup fully.

    What you need to do is use a 500k blend pot in conjunction with both 1M volume and tone pots. The resistance to ground is then restored to the proper 1 / (1/1M + 1/1M + 1/500k) = 250k.

    I hit this problem in a particularly bad way as I am using a coil tap and also a phasing push / pull switch on my control pots and locating 1M audio taper push / pull pots is rather difficult. I did find them though, and I think the results will be totally worth it, not only on dialing in-phase tone combinations, but also dialing in out of phase combos.

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    Quote Originally Posted by Neal View Post
    I'm wiring a 2-humbucker guitar with a volume, tone and blend (or pan) pot, with the blend pot taking the place of the normal 3-position switch. I bought a pan pot from Stewart MacDonald, 500K.
    Here's a link to the wiring diagram from the Stew-Mac site:

    blend pot
    In practice, both pickups sound muddy and dull. Looking at the diagram, it seems to me that I now have two 500K pots in parallel (the pan pot and the volume pot), in essence giving me 250K to ground. This would be like putting a 250K volume pot in a Les Paul. Am I reading this wrong, or is there a better way to wire this up?
    Yeah, I didn't realize that until I drew out the schematic. You're right about the 250k. If you want to put a blend pot in a Les Paul, you need a 1M blend pot, and then on top of it, 1M volume and tone pots as well. I haven't managed to find a 1M blend pot yet. If they don't exist, other options would be using push / pull pots to lift either of the pickups off the blend pot; then you could get a 50% blend, plus 25% in either direction off center, or both extremes of isolated pickups.

    Another option is to use 2 volume pots, but I hate doing that. I'm drawing up a circuit for it now, and the problem there is that you are still going to get some color from the other pickup. So I'm trying to figure out a way to get a "single pickup switch", an "out of phase switch", and a "split coil switch" which still lets me get both isolated pickups. Not succeeding at that so far, maybe if I use a virtual ground I can combine it cleverly with the phase switch to make the "single pickup switch" switch between treble and bass pickups when in single pickup mode.

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    hey folks. I'm in this same situation right now. I have a 500k blend 1meg V and 1 meg Tone. Any updates on the outcome of above??
    thanks

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    Quote Originally Posted by bellybuster View Post
    hey folks. I'm in this same situation right now. I have a 500k blend 1meg V and 1 meg Tone. Any updates on the outcome of above??
    thanks
    Yah, I did something pretty unusual though. I was too scared of tone suck with a volume pot and blend pot, so I removed the volume! I now have a PMT Humbucker Control Pot (lets me pan from single coil to full humbucking mode) instead. Not sure what the load is on this. It could be made in such a way that there is no load at full clockwise, which the product literature says, and I admit I didn't really believe, but it seems to be the case. BTW, I tried the "filter" mode on the humbuckers, and I almost couldn't tell the difference between zero and full clockwise - however "tap" mode worked exactly as expected, and is hum-cancelling if the pickups are fairly well matched as it pairs inner coil of one humbucker with outer coil of the other.

    I converted my tone pot to a 1M no-load pot as well (self made). Not sure I liked this mod too much. I will probably replace it with a standard 1M tone. When going open to no-load, there is a lot of high frequency coming back in the signal - high frequency noise that the low pass filter was cutting out before. I am a high gain player, so this might not matter in other circumstances. There is like 5-10% more brightness coming through when going open, some people might like that

    I'm using the blend to blend between an Air Norton and Tone Zone. All I can say is holy shit. Harmonics fly out of this thing and there is so much detail that seemed missing with the stock pickups. With pickup height adjustment added to the number of variables, there is no tone I can't get out of this guitar. EVH - check. Buckethead - check. Dave Navarro - check. This transformed what sounded to me more like a rock guitar (PRS Custom 24 with HFS / Vintage bass) into a metal soloing guitar, exactly as intended, with so much flexibility of tone. I'm still looking to nail the Kalmah guitar tone (e.g., intro to "Hades"), but I think I should be able to get that once I get the amp settings right. Oh yeah, and repair my Bloody Murder. Trashed the op-amp with reversed polarity power

    As for the missing volume control, I have a rack mount CryBaby wah, I plan to get another pedal for volume control. I like the idea of being able to do volume swells, which is something I could never pull off with a knob. My volume control is permanently at 10 anyway, unless going direct into gear, in which case, I can just use the input level trim to cut any output I don't need.

    So my experience with a passive blend mod is entirely positive and entirely awesome. I would probably have not been as happy if I left the volume control in, but I can't say for sure. Actually, I probably could try it with a passive volume pedal and see if the suck is as bad as I was expecting, but I'm too lazy to properly record it and A/B test anyway, and right now the baby is sleeping, so I'd only be able to do it with the Kemper, and I would expect a real amp to suffer more from passive suck than something with auto-levelling inputs.

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    Do your mag pickup blending into a buffer with the volume control after the buffer or interstage. I do this on my Electroline Piezo + Mag + Mag basses...the mags blend passively and then that combo, whatever it is, blends actively with the piezo. You can also then adjust the impedance load as you like it at the input of the preamp. You can have it both ways...

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    Quote Originally Posted by Rick Turner View Post
    Do your mag pickup blending into a buffer with the volume control after the buffer or interstage. I do this on my Electroline Piezo + Mag + Mag basses...the mags blend passively and then that combo, whatever it is, blends actively with the piezo. You can also then adjust the impedance load as you like it at the input of the preamp. You can have it both ways...
    If you want to blend a piezo bridge with passive pups, you'll need to do that. I think bellybusters question was about purely passive pickup blending though.

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    You'll notice that I said that I mix magnetics together passively and then mix that actively with the piezo. But the blend pot(s) (500 K per section) are the only "extra" load on the mags before they hit a 1 meg input, so I don't feel too bad about it, and it sounds just fine. A nice alternative scheme is wiring the mag pickups in series with a PU select switch, a DPDT on-off-on for simple.

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