Pickup blending - why does rolling back one volume cut that pickup?

[StringCanvas]

Not really. A blend knob is electrically identical to two volume knobs. It’s the same passive circuit. And adding an additional master volume just adds loading and dulls the tone more.

Disconnecting the ground from the blend changes it from a pair of volume controls to a pair of rheostats, adding series resistance to each pickup. This does smooth out the apparent taper of the sweep, and makes a more gradual difference as it’s turned.

Thanks for the info! I'm just trying to learn, so I'm sorry if the follow up is silly. I always appreciate how knowledgable people here are.
Here are two diagrams for J Bass wirings (one with a blend and one with classic V-V-T). When you say to disconnect the ground from the blend, I image you're describing the blue arrow in diagram 1, correct? The red would leave the V pot ungrounded.
If I'm understand that correctly (and there's a decent chance I'm not), does removing the blue arrow in diagram 2 accomplish the same thing? I'd assume not because they're all still grounded to the same circuit when they meet at the tone knob (or straight to jack if you're skipping the tone knob). Is there a way to accomplish the V/V blending?

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[ctmullins]

Thanks for the info! I'm just trying to learn, so I'm sorry if the follow up is silly. I always appreciate how knowledgable people here are.
Here are two diagrams for J Bass wirings (one with a blend and one with classic V-V-T). When you say to disconnect the ground from the blend, I image you're describing the blue arrow in diagram 1, correct? The red would leave the V pot ungrounded.
If I'm understand that correctly (and there's a decent chance I'm not), does removing the blue arrow in diagram 2 accomplish the same thing? I'd assume not because they're all still grounded to the same circuit when they meet at the tone knob (or straight to jack if you're skipping the tone knob). Is there a way to accomplish the V/V blending?
View attachment 7412186. View attachment 7412188

There are no silly questions! This is how we learn.

For diagram 1, yes, correct.

For diagram 2 - removing that wire would turn the upper volume pot into a rheostat, gradually dimming the upper pickup. The lower volume pot would still work correctly. The only caveat is that - if these pots are mounted to a traditional metal Jazz control plate, it would also provide a ground connection, making the black ground wires between the pots redundant (but still a good feature, as a backup ground path).

 

[bcbassman]

I accidentally miswired a bass once and ended up with an interesting result. When I backed one pickup off everything worked fine, until I got it all or nearly all the way shut off, then it killed both pickups. I think I saw somewhere this was Les Paul wiring as opposed to Jazz Bass wiring? Does anybody know?

All Gibson two pickup guitars have this wiring that dumps the volume if either of the pickups is turned off. I don't like it for bass.
You may have another opinion.

 

[StringCanvas]

There are no silly questions! This is how we learn.

For diagram 1, yes, correct.

For diagram 2 - removing that wire would turn the upper volume pot into a rheostat, gradually dimming the upper pickup. The lower volume pot would still work correctly. The only caveat is that - if these pots are mounted to a traditional metal Jazz control plate, it would also provide a ground connection, making the black ground wires between the pots redundant (but still a good feature, as a backup ground path).

I think I understand. So in diagram 2, if that blue arrow were disconnected and the pots were direct mounted or mounted to something like a plastic p bass guard, the top pot would almost work in reverse (all the way "off" would allow full pickup, gradually reducing the sound as it moves towards "on"?). If that's right, you could blend the pickups just knowing that one knob works in reverse (not the most elegant, but functional if nothing else). The pickups would be grounded to the pots, and the pots would still have to go to the ground side of the jack or tone pot?