Jazz Bass Incorrect Pots

[Omnipharious]

About a year ago now I picked up a '05 Squier Jazz, that I later found out somebody refinished, rerouted a little, swapped the neck pickup for a Lace Sensor, and they seem to have switched the pots up a bit. I moved the Lace Sensor (neck) to the bridge pickup slot, and put the bridge pickup in the neck slot. I am still learning about the different types of pots, so I am not sure if I am stating this problem perfectly correct, but here it goes.

When the tone is on (Fender wiring, clockwise) the pickups turn on, separately, at an odd rate. It is pretty close to linear sounding, but it seems to move up very slowly from the off-position, speed up in the middle, and slow down again towards the on-position. This happens for both pickups, but when one is all the way on, and I turn the other pickup up, it does nothing until the very end- probably 9 out of 10. It just clicks on when another is all the way active. The only way I have found to actually blend the pickups is to turn them both down to about 9, then turn them very slowly, very slightly up or down; even then it still has a tendency to turn the one with the lower volume off if there is too much of a difference in level between the two.

Now the tone, it clicks on no matter what. It is all the way on from about 10 to about 3, then it turns off at about 2.5, and stays that way the rest of the way to 0. When the tone is on, like I said, single pickups can be turned up almost correctly, but when the tone is off, the pickups click on at about 9 when turning single pickups on, or both together.

I took the pots out, and both volume pots say they are "A250K", and the tone says it's a "B250K", which I heard is right- which should make the volumes logarithmic, and the tone linear- but these pots seem to be backwards. I heard that there is no real standard for what is labeled A's, or B's, and that different companies do it what ever way they want, but I cannot tell what company makes these pickups. They look exactly like the ProLine's I ordered for a different guitar; but the ProLine "B500K" seems to be logarithmic, not linear.

Could these pots be labeled backwards, and could it be linear pots for volumes, and a logarithmic for the tone?

[Stealth]

Yes, they could, depending on how old the pots are. At one point A was linear and B was log.

[walterw]

Nah, if we're talking about regular newer imports, then "A" is audio, and "B" is linear.

They're behaving pretty much exactly like I'd expect, which is why you actually want linear volumes and an audio tone.

[Omnipharious]

Originally Posted by walterw

Nah, if we're talking about regular newer imports, then "A" is audio, and "B" is linear.

They're behaving pretty much exactly like I'd expect, which is why you actually want linear volumes and an audio tone.

None of my other guitars do that, and I hate that this one does, so that doesn't sound like they are correct to me.

[SGD Lutherie]

Originally Posted by Omnipharious

None of my other guitars do that, and I hate that this one does, so that doesn't sound like they are correct to me.

Which of your guitars have two volume controls wired up like a Jazz bass? I bet none of them. Most guitars with two volume controls wire them up like a Gibson, which is totally different.

What Walter is saying is fact, and is the basis of the problem. because of the way the two controls interact, you need linear taper (B) for volume and audio taper (A) for tone. Also, when you do use audio or log taper pots for volume, there are different rates. The standard is 10% of the taper when the pot is at half way, but there are other types as well. Also these days log taper pots are not really log taper, but are several linear tapers composted together. So they aren't always all that great.

Some of us have been rewiring basses like this for a long time, so we have seen this problem over and over again. Linear taper works beat for Jazz basses.

[Omnipharious]

Originally Posted by SGD Lutherie

Which of your guitars have two volume controls wired up like a Jazz bass? I bet none of them. Most guitars with two volume controls wire them up like a Gibson, which is totally different.

What Walter is saying is fact, and is the basis of the problem. because of the way the two controls interact, you need linear taper (B) for volume and audio taper (A) for tone. Also, when you do use audio or log taper pots for volume, there are different rates. The standard is 10% of the taper when the pot is at half way, but there are other types as well. Also these days log taper pots are not really log taper, but are several linear tapers composted together. So they aren't always all that great.

Some of us have been rewiring basses like this for a long time, so we have seen this problem over and over again. Linear taper works beat for Jazz basses.

Yeah, sorry if I sounded like I knew everything, I do that sometimes

I wondered why they interacted differently with each other. I'm still sure something isn't right then, because I took all the wires off them, broke out my meter, and did a few tests.

The control plate is flipped over, with pots in place, upside down, knobs in the cavity. Starting with the volume pots, I put the black clip on the center lug, and the red on the right lug. I notice something right away, with the knob all the way off, there is still some slight signal coming through; the needle isn't going all the way down (is that normal?). I start to turn it and it doesn't start to move until about 2 or 3, then from there it speeds up exponentially. But, then when I put the red clip on the left lug, and black on the center, I turn the knob from the (now) off position, and it doesn't move the needle until about that same 2 or 3 point, then it jumps all the way to the right from there. Why is it different for either side, and wouldn't the movement of it make this a log pot?

For the tone, black clip on center, red clip on right lug, from the off position, the needle doesn't start to move until about 6 or 7, then goes all the way up between about there and 8 or 9. It acts the same with the red clip on the opposite lug. What kind of pot would that make this?

[walterw]

that would be audio taper for the "A" pots and linear taper for the "B" pot, like we said.

for laughs, try swapping the tone pot with the neck volume pot. you should find that the neck volume now comes up and down more evenly, without the "kick" near "10", and the tone pot now does something through its whole range rather than all action happening near "0".

[walterw]

either way, you also run into the interactive nature of this circuit: since the tone pot is necessarily run to the outputs of the volume pots, turning one down a little affects the way the other behaves.

rolling the tone back a bit will make the volumes drop off even faster from "10", while rolling the volume back a bit will make the tone act like another volume for the first part of its drop.

[Omnipharious]

Okay, I just wanted to make sure I wasn't getting the wrong informaiton because I was explaining it wrong. If I switched both volume pots for linear pots, instead of just doing one, and put one of the logarithmic pots in the tone position, would that allow me to almost blend the pickups, and adjust the tone linearily? Because I really love the sound of the pickups where they are, but I'm not the biggest fan of the tone when it's all the way off, and with the setup as it is, there really only is an on, and off.

[walterw]

yep, exactly that.

i suggested the swap as something you could do now, to test it. with a linear neck volume, it would be a bit easier to find the "sweet spot" where you start with both full-up, then turn down the neck until the tone just starts to change, bringing in the midrange growl.

[Omnipharious]

Huh, okay. I'll test that tonight, and if it works just as you say, I guess I'll be ordering a good few pots from somewhere. Just one question, if the tone pot right now is a linear taper, why did it react the way it did for my meter when disconnected from everything? It wasn't linear movement at all; from about 7-9 it goes from all the way off to all the way on.

[walterw]

Originally Posted by Omnipharious

For the tone, black clip on center, red clip on right lug, from the off position, the needle doesn't start to move until about 6 or 7, then goes all the way up between about there and 8 or 9. It acts the same with the red clip on the opposite lug. What kind of pot would that make this?

that's what makes it linear, that one direction is the same as the other. the rest i would just put down to the way your meter is behaving.

[Omnipharious]

So it not moving up at a steady rate you think is a problem with my meter? I have had to adjust it a bit more lately, so I should find a few new batteries, but it seems pretty far off for just being my meter.

[SGD Lutherie]

Here's how audio vs. linear tapers work:

The Log and Short of Tapers - Premier Guitar

[walterw]

Originally Posted by Omnipharious

So it not moving up at a steady rate you think is a problem with my meter? I have had to adjust it a bit more lately, so I should find a few new batteries, but it seems pretty far off for just being my meter.

i actually have little experience with the old needle-style ohmmeters.

is there a range setting for different impedances? that might be throwing off the way the needle responds.

regardless, a linear will respond the same way in both directions, while the audio will "jump" early in one direction, and jump late in the other.

it's all about the actual circuit the pot is in (including the circuit through your meter) that creates the result;

linear volume=smooth volume increase through a clean amp

linear tone=little effect until the tone is almost at "0".

audio volume=quiet from "0", jumps at "8" or "9" through a clean amp

audio tone=normal tone knob sweep

[walterw]

i say "through a clean amp" because with guitars, and their crunchy, compressed tube amps, you want audio volumes to fight the compression and clean up the drive as you turn down.

you want audio tones regardless.

[Omnipharious]

That is only for the jazz circuit, right? And for regular one pickup-one vol-one tone/two pickup-two vol-two tone type circuit it is the opposite, right? (in regard to the linear-vs-audio description)

[walterw]

no!

for a P-bass, you'd still want a linear volume and an audio tone.