Jazz Bass re-wiring

[tekdiver500ft]

I couldn't find anything on point, so I'm going to ask it here.

I have a bad pot (neck pickup) on my Squier VM Jazz, and only use my bass with both volumes all the way up (humbucking) anyway. So, I want to eliminate the neck volume, and use the bridge volume as master volume, and keep the tone control as is. I want to keep both pickups, and keep them at equal output at all times. How do I wire this correctly? I could figure it out through trial and error, but would prefer to get it right on the first go 'round.

Thanks so much for your help

[Stealth]

You start off with a total of four wires, two from each pickup.
Wire the pickups in parallel (solder wires white-to-white, black-to-black) so now you effectively have two wires. Now, look up the Precision bass schematic (this one for instance) and wire the two new wires according to that (one to the volume pot, other to ground).

[tekdiver500ft]

Outstanding, thanks for the help!

[MglMatador]

Originally Posted by Stealth

You start off with a total of four wires, two from each pickup.
Wire the pickups in parallel (solder wires white-to-white, black-to-black) so now you effectively have two wires. Now, look up the Precision bass schematic (this one for instance) and wire the two new wires according to that (one to the volume pot, other to ground).

Resistive loading of the pickups is going to be different if done this way....if you want the setup to sound the same, you need a resistor soldered between the two 'new' leads to simulate the load of the previous (and now gone) volume pot (either a 250K or a 500K to match what was taken out).

[line6man]

Originally Posted by MglMatador

Resistive loading of the pickups is going to be different if done this way....if you want the setup to sound the same, you need a resistor soldered between the two 'new' leads to simulate the load of the previous (and now gone) volume pot (either a 250K or a 500K to match what was taken out).

Or just use the old pot as a load.

[walterw]

You guys are correct, but might be making this more complicated than it needs to be.

Just solder the neck pickup wires exactly on top of the bridge pickup wires, and you're done.

[line6man]

Originally Posted by walterw

Just solder the neck pickup wires exactly on top of the bridge pickup wires, and you're done.

No, then you would still have a variable impedance load on the pickups when you adjust the volume. The OP should take this opportunity to wire the wiper terminal as an output, so the pickups will see a constant resistive load.

[tekdiver500ft]

Actually, the OP should learn not to jump to conclusions. I opened it up to do the re-wire, and lo and behold, there was only one strand of the wire attached to the neck volume pot. I re-soldered that, and all is well. [Call me Homer (D'OH!!!)!]

[kb9wyz]

Originally Posted by line6man

No, then you would still have a variable impedance load on the pickups when you adjust the volume. The OP should take this opportunity to wire the wiper terminal as an output, so the pickups will see a constant resistive load.

Walter was right. There is electrical difference between what he said and running both pups at full volume with two pots.

Impedance variance doesn't really count into it because different inductance for the pups and different volume levels for each pup (either two pots or a blend) constantly change the impedance between each leg of the circuit.

Also, from what I've seen (which is not exhaustive) the pups in a J tend to have different impedances from each other. That is to say the inductive, capacitive, and resistive characteristics of each pup will not be identical. On purpose. (check out the chart or passive J pups: Seymour Duncan )

So between the volume/blend knobs and the pups themselves, impedance is like a sausage factory. You are never sure what goes into it but as long as whatever comes out of it is pleasant, it just doesn't matter.

[kb9wyz]

Originally Posted by tekdiver500ft

Actually, the OP should learn not to jump to conclusions. I opened it up to do the re-wire, and lo and behold, there was only one strand of the wire attached to the neck volume pot. I re-soldered that, and all is well. [Call me Homer (D'OH!!!)!]

AWESOME!

[line6man]

Originally Posted by kb9wyz

Walter was right. There is electrical difference between what he said and running both pups at full volume with two pots.

Impedance variance doesn't really count into it because different inductance for the pups and different volume levels for each pup (either two pots or a blend) constantly change the impedance between each leg of the circuit.

Also, from what I've seen (which is not exhaustive) the pups in a J tend to have different impedances from each other. That is to say the inductive, capacitive, and resistive characteristics of each pup will not be identical. On purpose. (check out the chart or passive J pups: Seymour Duncan )

So between the volume/blend knobs and the pups themselves, impedance is like a sausage factory. You are never sure what goes into it but as long as whatever comes out of it is pleasant, it just doesn't matter.

What the hell are you talking about?

Look at how a voltage divider circuit works.
When you have two volumes, the pickups have to be wired to the wiper terminals, otherwise rolling either volume all the way down would mute both pickups. The problem is, as you roll the volume pot down, the resistance between the signal and ground is reduced as the series resistance between the pickup and the output increases. When you only have one volume pot, you can take advantage of the oppurtunity to wire the wiper terminal as an output, that way, the pickup(s) see a constant resistance that does not change as you roll the volume down. The resistance at the wiper terminal gets varied against the output, but basses are almost always plugged into high impedance inputs, so it doesn't matter.

If you wire the bass P bass style, with the wiper terminal as an output, the volume pot should work a lot better.

FWIW, when I said "variable impedance load," I was referring to a purely resistive impedance with no complex part, from the volume pot. That probably caused confusion.

[kb9wyz]

Originally Posted by line6man

What the hell are you talking about?

FWIW, when I said "variable impedance load," I was referring to a purely resistive impedance with no complex part, from the volume pot. That probably caused confusion.

I am the hell not talking about a voltage divider. For exactly the reasons you point out. The pups should always be in parallel. Maybe I should have said that.

My understanding of what Walter was saying was to hardwire the pups in parallel, so there shouldn't be any impedance issues. This is what I was thinking he meant and what the OP was asking:

-+-------+------------0 (+V)
-|-------|
C||-----C||
C||-----C|| (PUPS)
C||-----C||
C||-----C||
-|-------|
+---+---+
-----|
-----|
----->/
-----> (Vol Pot)
----/ >
-----|
-----|
-----0 (GND)

Throw the tone in the right place because I'm done with that business. (Typing components is a losing battle) Then I assumed he meant to take the other volume pot out of the circuit because it wouldn't be necessary anymore.

Don't think we were at all on the same page. Oops.

And you're right about the impedance thing. Since impedance is by definition the total of all resistance and reactance, I assumed you were talking about those components as well.

[line6man]

Originally Posted by kb9wyz

I am the hell not talking about a voltage divider. For exactly the reasons you point out. The pups should always be in parallel. Maybe I should have said that.

My understanding of what Walter was saying was to hardwire the pups in parallel, so there shouldn't be any impedance issues. This is what I was thinking he meant and what the OP was asking:

-+-------+------------0 (+V)
-|-------|
C||-----C||
C||-----C|| (PUPS)
C||-----C||
C||-----C||
-|-------|
+---+---+
-----|
-----|
----->/
-----> (Vol Pot)
----/ >
-----|
-----|
-----0 (GND)

Throw the tone in the right place because I'm done with that business. (Typing components is a losing battle) Then I assumed he meant to take the other volume pot out of the circuit because it wouldn't be necessary anymore.

Don't think we were at all on the same page. Oops.

And you're right about the impedance thing. Since impedance is by definition the total of all resistance and reactance, I assumed you were talking about those components as well.

Walter was saying to just take the neck pickup's hot and move it to the bridge pickup's volume pot's wiper terminal.
This allows the pickups to be in parallel with a master volume pot, and the total resistance parallel to the signal will stay the same as it was. The issue I was addressing, however, was that it's more preferable to also swap the input and output of the volume pot around. It takes a tad more effort, but it's a better way to wire the bass.

[walterw]

line6man is right about that (and i wasn't thinking of it at the time).

with one volume, there's no reason to suffer the tonal compromises of having the pickup(s) on the wiper instead of the proper input terminal. you'd absolutely want to swap that around.

[tekdiver500ft]

While I no longer "have" to wire the bass this way, I'm wondering if doing so will keep the pickups humbucking at any volume, since they will be tied together? I play with them together 90% of the time, and hate that single coil buzz when they are offset. Yes, it limits my tone options, but I really only want P bass sound anyway. I got the J for the fretless J neck, not the sound.

Any tips for getting a good P sound from a set of Seymour Duncan J pickups?

[walterw]

yes, wiring them both to one pot (and swapping the pot "hot" leads as line6man reminded us) would give you always hum-cancelling, because it would only be the "both pickups at the same time" sound.

it wouldn't be anything like a P-bass, though. the closest you'll get to that is dialing the neck pickup in by itself and just living with the hum.