Blend potentiometer arithmetic (pot values, active and passive)

[Adieu]

Looking to experiment with a blend pot for pickup selection, between an active pup (EMG 89) and a passive pup (Super 70), in a good old Les Paul copy. Idea is that it'll take care of the expected output difference when panned somewhat toward the Super 70, or allow a small bit of classical flavour to bleed through from the raunchy A8 passive and spice up the sterile-ish active tone w/ the EMG at full blast.

After some doubts and a whole bunch of thinking, I've arrived at placing the Super 70 in the bridge, EMG 89 in the neck, flipped (like an EMG 89R - to get the single coil located under the harmonic "sweet spot" that would be the 24th fret, if the fretboard went that far). Reasoning: a) sweet spot, b) super 70 in neck gets too muddy and has too much sustain-killing stringpull (downside of A8), which is why I pulled one of the pups from the guitar to begin with.

So... blend pot values. After searching far and wide, I finally procured two blend potentiiometers - a 250k and a 500k. All I could find. Bought em both.


Now, I'll probably want at least a master volume, since the blend pot never shuts anything off, just pans between the pickups... I'm also forced to use the 25k push-pull that came with the EMG 89 to properly wire up & operate it to the full potential. Well, almost full, since it still doesn't allow mixing the humbucker and singlecoil signals, just either/or (hmm, maybe a 3way switch? not sure how to wire it, though, anyone know?). Also, I'm not exactly sure what a 25k would do, especially stacking values with the 250 or 500k blend pot, to the passive part of the signal.


SO - WHICH BLEND POT SHOULD I USE? And what about the volumes, independent 25k active and 500k passive? That would make for 260-ish kiloohms for the active, and 500 even for the passive (using the 500k blender), or 140ish on the active and 375 for the passive (using the 250k blender), right? So, 250k makes more sense right? With 25k-A/500k-P independent wiring before the pot? Or screw it, use the 25k push-pull for a master, since it'll average out to an inbetween value with the blend pot?

In that case, 250k Blend 25k Master for a 140ish average that right for neither passive nor active, but isn't as ridiculously far off in either direction (active pots run up to 50k, so 3x off for active, and 2-3x off from the 250-300-500k passive choices)?? 500k Blend 25k Master for 260ish average that's in the proper range for passives, but way off for the active???

OR is the whole logic inapplicable, and I should go with 250k Blend for blending and volume level purposes, and just use the 25k EMG push-pull to operate the 89 and as an "emergency master" - as a sort of kill pot if I get feedback or accidental earsplitting volumes, but otherwise keep it dimed and use amp/pedal volumes alone????

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THANKFUL FOR ANY INPUT - EXCEPT THE "you can't mix actives and passives you dimwit!!" CROWD - CAUSE I'VE DONE IT, WITH A BLEND POT TOO (inadvertently, by just trying the easiest possible wiring change) ON BASS BEFORE, AND IT WORKED. It even made some use of an utterly weak and otherwise useless trashy entry-level passive single coil, which paired up surprisingly well with the ridiculously powerful Seymour Duncan APB-2.

So, anyways, thanks in advance, what are your *constructive* thoughts here???

[Adieu]

Re: Blend potentiometer arithmetic (pot values, active and passive)

Aww cmon... no one???

[uOpt]

Re: Blend potentiometer arithmetic (pot values, active and passive)

You can't blend like that. The impedance of the pot for the active one will kill the passive pickup.

Even with two passive pickups guitarists generally cannot do what bassists do, which is connect the volume pots backwards to make them more independent, for a blend pot like in a Jazz bass. That kills the resonance peak when more than just one pickup is on. Bassists can afford to live without the resonance peak but guitarists almost never can, except for some very specific uses like some clean picking.

All will be fine if you have two active, including that SD preamp after the passive pickup.

[Adieu]

Re: Blend potentiometer arithmetic (pot values, active and passive)

You can't blend like that. The impedance of the pot for the active one will kill the passive pickup.

Even with two passive pickups guitarists generally cannot do what bassists do, which is connect the volume pots backwards to make them more independent, for a blend pot like in a Jazz bass. That kills the resonance peak when more than just one pickup is on. Bassists can afford to live without the resonance peak but guitarists almost never can, except for some very specific uses like some clean picking.

All will be fine if you have two active, including that SD preamp after the passive pickup.

The hell you can't... I'm telling you I've done it before. It kicked ass, and yes it was 1 active + 1 passive. BUT I was just leaving stock pots, whatever the heck they were - the blender, the passive, and the presumably-passive-ohmage volume & tone were already in the guitar. And I no longer own it to check what I used.

You can't preamp a Super 70, it's 2-conductor alas... wish it weren't, but it is what it is.

Impedance of pot? Uuuuhh....not sure which one of us hasn't a clue as to what he's talking about, but ONE of us is definitely wrong as can be.

Backwards volume pots? Uhm, like $7 gets you a proper stacked "blend/balance" potentiometer, with 2 "electrically independent but physically linked" pots controlled by the same shaft and the full 6 terminals, to wire up however you want - which includes a proper blend pot possibility.

[uOpt]

Re: Blend potentiometer arithmetic (pot values, active and passive)

If you already know it works fine for your expectations then what's the question.

In a passive guitar, connecting the pots backwards compared to normal wiring (pickup hot to middle lug) will kill the resonance peak earlier when tuning down the pot. It's the price you have to pay for the better independence. In practice, bassists are more willing to pay that price, but guitarists sometimes use it. It's one of those things that's sometimes labeled as "50s wiring".

If you already know that you can mix active and passive then why the question?

[Adieu]

Re: Blend potentiometer arithmetic (pot values, active and passive)

WHICH VALUES is the question. I have no idea what blend pot was in that axe I no longer have and don't have any way of checking anymore.

Also, Fender sells guitars with blend pots. One of the MIJ Pawn Shop series had a Pearly Gates and some Fender bucker with blend controls - worked awesome. And definitely could scream. One of my favourite guitars that I haven't owned, in fact.