Help with wiring concentric pots!

[Chuck]

Hi brains trust – some wiring question for the Bass IV build I’m. I’ve got three pickups that will each be wired to a “Jaguar-style” selector switch. From the switch, each pickup will go to its own concentric pot. Here’s a diagram I found online that shows how I need to wire the pots.



First question: the ground in this pic I’m assuming just goes to the back of the pot or does each one have to go to the ground on the jack? And if it is just to the back of the pot, which wire would go to the ground lug on the jack?

Second question: each of the “to jack” wires will go to the jack – so I’ll have three wires that will all be connected to one jack lug. Is that okay?

Third question: For the capacitors, I’m thinking I could use a .047 for each one, but I’ve read a .022 will let more mids through. Would any of you look at using different values for each pickup? I know I can just try (and perhaps will) but thought I’d seek some advice!

Finally: I’ve read about putting a .001 on the volume pot as it “sends higher frequencies to the ground and gets rid of noise”. Is this right, and whereabouts would I wire that in?

I’m not very good with electronics so please be gentle!

[Chuck]

And here are another couple of pics that does it a little differently... now I'm really confused!

[wokkaboy]

Hi Chuck, probably best wait for wiring guru Weirdy to reply. So I assume you want a tone control for each pickup so you can have different value caps on each pup ?
There should be an earth wire coming from the bridge or bridge plate and this will be earthed to a common place which is usually back of a volume pot. Then jack and switch and copper shielding should be connected to this common point.
I've never done this configuration but assume each of the 3 jack wires from each pot would all go to the hot tip of the jack.

As for cap values think work on recommended values for each pup and if you need to change one after experimentation it's not too hard. I'd order 3 different value caps x 3 and see what works for you

[Chuck]

Thanks Wok - yep, each pickup has it's own unique vol/tone control. And I think that second lot of pics I put up made the ground issue a little clearer for me!

[wokkaboy]

yeah that last pic makes it clearer. Just treat each concentric pot as a tone pot stacked ontop of a volume pot and follow the wiring diagram.
What is this axe the purple jazz bass with 3 single pickups ?

[Chuck]

What is this axe the purple jazz bass with 3 single pickups ?

Yep, the four string version of a Bass VI...

[WeirdBits]

Short on time just now, will answer with options tonight.

[WeirdBits]

As you have individual switches for the three pups you have two initial options for wiring: LP guitar style linked volumes or Jazz bass style independent volumes.

Linked volumes means that if you turn the volume to zero on any active (on) pickup then all active (on) pups will be muted. It allows you to quickly mute the guitar/bass just turning one volume. With lugs facing down, pickup to left lug, output on middle lug.

Independent volumes means that you can turn down any volume to zero without affecting the sound from any other pickup. Good for blending in/out different pups without needing to use the switch. With lugs facing down, pickup on middle lug, output on left lug.

Either way, you'll want to the output to the jack connected across the outs of your switches, with the pups wired as:

Pickup->concentric pot->individual switch->(output to jack)

That way any pot that's not tied to an active (on) pickup isn't in the circuit.

The volume ground lug and capacitor ground should link to the back of the pot, then have the pot casings linked via shielding or a ground wire to your main ground point or output jack. ie. Jack ground to back of first pot then wire/shielding links to the backs/casings of the other pots.

Guitars often use a treble bleed cap (~0.001uF) to allow high frequencies to pass directly to output rather than lose some of them to ground through the resistance of the volume pot. Intentionally bleeding them off to get rid of high-end noise on a bass is the opposite, the cap links to ground and everything above a certain frequency goes straight to ground through the cap. If you wire and shield the guitar/bass well then noise really shouldn't be an issue, so you can just use your tone pot with cap of choice to control how much of what freqs go to ground. Tone switches are a thing, a switch with a specific cap either off or full on, but are more to shape particular sounds than to filter noise.

[Chuck]

As you have individual switches for the three pups you have two initial options for wiring: LP guitar style linked volumes or Jazz bass style independent volumes.

Linked volumes means that if you turn the volume to zero on any active (on) pickup then all active (on) pups will be muted. It allows you to quickly mute the guitar/bass just turning one volume. With lugs facing down, pickup to left lug, output on middle lug.

Independent volumes means that you can turn down any volume to zero without affecting the sound from any other pickup. Good for blending in/out different pups without needing to use the switch. With lugs facing down, pickup on middle lug, output on left lug.

Either way, you'll want to the output to the jack connected across the outs of your switches, with the pups wired as:

Pickup->concentric pot->individual switch->(output to jack)

That way any pot that's not tied to an active (on) pickup isn't in the circuit.

The volume ground lug and capacitor ground should link to the back of the pot, then have the pot casings linked via shielding or a ground wire to your main ground point or output jack. ie. Jack ground to back of first pot then wire/shielding links to the backs/casings of the other pots.

Guitars often use a treble bleed cap (~0.001uF) to allow high frequencies to pass directly to output rather than lose some of them to ground through the resistance of the volume pot. Intentionally bleeding them off to get rid of high-end noise on a bass is the opposite, the cap links to ground and everything above a certain frequency goes straight to ground through the cap. If you wire and shield the guitar/bass well then noise really shouldn't be an issue, so you can just use your tone pot with cap of choice to control how much of what freqs go to ground. Tone switches are a thing, a switch with a specific cap either off or full on, but are more to shape particular sounds than to filter noise.

Thanks Weirdy, that's starting to make it a little bit more clear!

I'm looking at the jazz bass style independent volumes - so that would be the first diagram I posted I'm guessing?

I'd also (now incorrectly) thought I should go pickup->switch->pot->jack so that's for clearing that one up for me too!

Re the capacitors (as per the first diagram) do you think .047 is a good option as a starting point? I know I could swap them out later although I'm not sure I fully understand the implications of the different values.

Once again, thanks heaps!

[WeirdBits]

Yep, the first diagram is the one you want for jazz style wiring. If you have a multimeter it's always a good idea to check you pots before you wire them to make sure their values are in the ballpark and that they work the way you expect etc.

For the caps, 0.047's are a good starting point. If you want you could maybe try an 0.068 on the bridge pup and 47's on the others, or something like that, just to see what sounds best in your particular build.

Caps work as filters with a cut-off frequency, everything above the cut-off can pass everything below gets blocked. The smaller the cap value the higher the cut-off frequency. So, from the above, an 0.068uF cap has a slightly lower cut-off frequency than a 0.047uF cap. The tone pot provides resistance (or flow control like a tap) that regulates how much of the freqs above the cut-off are allowed to pass to ground. The 'strangle' switch on a Bass VI is a cap inline with the output that only allows everything above the cut-off to pass to output, thereby cutting the bass.

StewMac used to have a general frequency diagram for caps, I'll see if I can find it: Try this...