Pot instead of 3 way switch

[Bizman62]

For my current build I was going to put a standard 3 way switch for the two single coils. The pickups are originally the mid and bridge of a Strat so played together they should sound something like the in between humbucking version.

Suddenly I remembered that I was planning to use a regular pot instead of a switch. I have an SSS Strat featuring a standard pot as a blender but I can't figure out how to do the same without a switch and a third pickup. I assume that would be very simple, though, for you guys who know your wires.

Here's the basic idea with ground wires. The rest is greek to me.

[curtisa]

Assyming you want proper nulling of each pickup at the extremes of the pot rotation I don't think it can be done without using something like the Stewmac blend pot.

Note that the tapers of each wafer in the dedicated blend pot are customised so that at mid-rotation the outputs of both pickups are at maximum. Doing the same thing with a regular dual gang pot results in both pickups being heavily slugged at the midpoint, and only reaching maximum output at the extreme ends of rotation.

I think there *is* a way to do a two-pickup blend using a single gang pot, but again it results in compromises in terms of being able to achieve full volume from each pickup and leaving extra resistance in series with each pickup, which is probably not desirable.

[Bizman62]

6 hours ago, curtisa said:

Assyming you want proper nulling of each pickup at the extremes of the pot rotation

No, I'm aware that regular pots leak a bit and I'm fine with that thought. My Strat does just that and it sounds great. Here's how that's wired, the image is grabbed from a Breja ToneWorks video which doesn't seem to be available any longer:

Looking at the Strat drawing and omitting the mid pickup it looks like the green wire goes straight to the left lug and the red wire to the middle lug. So the main issue is the purple wire connected to the Volume pot: Where should the other end go? To the right lug of the Blender?

[henrim]

I'd use a potentiometer made for the job. Like this Bourns dual gang pot available for example from Digikey.fi. Other makes are available too.

Or you may consider just wiring separate volumes for the two pickups and mix the signal with the volume pots.

[Bizman62]

Thanks.

I know about the dual gang pots and when searching for information the separate volumes idea was also frequently brought up.

But I really just want to use what I have at home, this is for the guitar made of scrap pieces and donationware. And since the Strat works fine with a regular pot I'd like to test that idea with just two pickups.

[curtisa]

19 hours ago, Bizman62 said:

No, I'm aware that regular pots leak a bit and I'm fine with that thought

It's not that they 'leak' - the way the pot is configured means it either cannot fully 'shut off' or 'open up' the pickup.

But if you're happy with that quirk, the below (untested!) idea should work with a standard single gang pot:

 

Limitations;

• With the blend pot at each extreme the pickup will have an extra 22k resistance inserted in series with the hot lead which will darken the tone a bit
• The blend pot at each extreme will give half output compared to that same pickup should it have been wired direct to a volume pot.
• The blend pot at 50% rotation will not give you full output on both pickups (probably less than half output from both)
• The blend pot needs to be linear taper to have equal rates of cross-fading. Even then, the perceived taper might feel a bit odd (an initial quick rise in volume followed by a long period of little perceived change as you rotate the pot is likely).

In all honesty the dual-gang blend pot linked to by @henrim, or his suggestion of independent volume pots that you set the blend with is the way to go if you want to combine two pickups arbitrarily.

[Bizman62]

4 hours ago, curtisa said:

It's not that they 'leak' - the way the pot is configured means it either cannot fully 'shut off' or 'open up' the pickup.

That's what I meant, I just can't speak Electronish that well.

As the other pickup will always have some effect, will there also be a humbucking effect in every position of the pot?

And if I choose a 500k pot for the blender, would I still need the 22k resistors? There's none in the Breja drawing for Strat.

This will be an experimentation, easy enough to change to a 3 way switch or a real blender pot if I'm not happy.

[curtisa]

1 hour ago, Bizman62 said:

As the other pickup will always have some effect, will there also be a humbucking effect in every position of the pot?

Only while the two coils are equally set. Ie, with the pot at mid rotation. Once the blend drifts off to one side or the other the humbucking ability gets gradually knobbled.

Edit: in case I wasn't being clear, the circuit I proposed *does* shut off the opposite pickup fully when the pot is turned to each end. It's just that true 'full volume' operation will always carry some baggage.

 

1 hour ago, Bizman62 said:

And if I choose a 500k pot for the blender, would I still need the 22k resistors?

Yes. The two resistors act as passive mixers. Without them you'll only get a blended mix of the two pickups in the middle of the pot rotation and nothing at all at both extremes of the pot. You may be able to fiddle with the values of pot and resistors to get a bit more useful range. But the two resistors need to be equal, and you'll always have less/darker output than you would with a dedicated blend pot or independent volume controls.

 

1 hour ago, Bizman62 said:

There's none in the Breja drawing for Strat.

The Breja scheme only acts as a [neck-at-100%-plus-variable-other-pickup] function. And it does it with the afore-mentioned issue of never being able to completely isolate or properly control the volume of the blended pickup. Your requirement to blend the two pickups in varying inversely-proportional amounts complicates things a little more, hence the extra mixing resistors.

[Bizman62]

7 hours ago, curtisa said:

The Breja scheme only acts as a [neck-at-100%-plus-variable-other-pickup] function. And it does it with the afore-mentioned issue of never being able to completely isolate or properly control the volume of the blended pickup.

Oh? This made me do some testing and you're right, it does exactly that. Plus some more: The dominant pickup changes depending on the switch. So basically if I wanted the Breja scheme to work with two pickups similarly to the Strat I'd need a two way switch, or a three-way for a full "both" sound?

[Bizman62]

Oh, and now that I've been a bit more educated about various blender options: I've been toying with the idea of having a sliding pot instead of a blade switch. As has been said a real blender/fader pot would work just as imagined, keeping the output stable and mixing the two pickups logically.

The big question is, would impedance matter? There's tons of pots available at 100k but trying to find just one or two at 250k or 500k with a sturdy metal slider and of compatible length seems to be a mission impossible. I once found some but they never arrived despite the vendor saying so. Most likely they were stuck at the Customs until they were considered as "delivered but rejected".

[curtisa]

4 hours ago, Bizman62 said:

The dominant pickup changes depending on the switch.

Correct - in the bridge position you're blending the neck back in with the pot, but in the neck position you're doing the inverse and blending the bridge back in. In the 'in-between' positions it gets weirder as you're also adding the middle pickup to that behaviour. I can see why it was offered as a quick mod, as it uses the parts that are already fitted to a Strat. But it's a bit of a hot mess really, and could be one reason why he no longer has it on his YT channel.

 

4 hours ago, Bizman62 said:

So basically if I wanted the Breja scheme to work with two pickups similarly to the Strat I'd need a two way switch, or a three-way for a full "both" sound?

I'd have to have a think about it - I'm actually not sure you can do what the Breja blend scheme was trying to do using standard parts without it being severely compromised in the way it operates.

 

2 hours ago, Bizman62 said:

I've been toying with the idea of having a sliding pot instead of a blade switch. As has been said a real blender/fader pot would work just as imagined,

I think you're going to get the same limitations as the single-gang pot blend I suggested, above. A linear-motion fader is the same as a rotary pot, just with the resistive wafer straightened out from its horseshoe pattern into a straight line. Further, I don't think a true blending fader (like the pot @henrim linked to) is something that can be bought off the shelf.

Pretty sure if you lowered the value of the pot (whether fader or rotary) to 100k the tone would darken a little more, but it should still work (inasmuch that it 'works' with the same oddities as previously indicated).

[Bizman62]

11 hours ago, curtisa said:

Further, I don't think a true blending fader (like the pot @henrim linked to) is something that can be bought off the shelf.

Oh, they do exist. "Dual gang slider" seems to be the key phrase, and surprisingly enough there's many that would fit closely to the screw holes of a blade switch but as said the ohm values are rather low, 10 k is more common than 100k. And the shafts are mainly plastic. I just found one from a Finnish international site, 10k made by Bourns, temporarily out of stock and delivery after September 2024! The price was tolerable for a single item. But the ohmage...

[curtisa]

12 minutes ago, Bizman62 said:

Oh, they do exist. "Dual gang slider" seems to be the key phrase

But they won't have the required taper to make them behave the same as the purpose-made blender pot. If you use a linear dual gang fader it will be the same as a linear dual gang rotary pot - you'll get full volume from each pickup at the extremes, but half volume from both in the middle.

Higher values of resistance in a fader are usually pretty rare. Anything over 100k will be quite specialised.

[Bizman62]

2 minutes ago, curtisa said:

Anything over 100k will be quite specialised.

That's true. Back when I spent more time I could find just what I wanted, with center notch and all, and the tapers were at full height at both ends - a basic stereo pot for panning between left and right speaker. The issue was that the sites I found the right models and values were those of manufacturers and I certainly don't need a sea container full of them!

[henrim]

My not be an easy option but, if I really really wanted a linear control but couldn't source a commercial one, I'd drive a rotary potentiometer with rack and pinion. Or with belt, thread, rubber band or something.

[Bizman62]

A horizontal pot would also work but they come in very small diameters, 10 or even 15 mm is way too small to be used as a blender. Plus the movement range would be too large for a visual marker.