Modify PJ wiring to bypass bridge pickup.

[mcnach]

I've got a PJ, well...actually a P/JJ, where the bridge pickup is a dual J wired as a humbucker.

Wiring is VVT.

The JJ can be split to give a single coil alone, with a pull/push switch located on the tone control.

When I use only the P pickup, the sound is noticeably affected by using the split coil switch, sounding a lot more "Precision" when in single coil mode, even if the JJ volume is off completely.

I'm thinking I'd like to install a mini switch that bypasses the bridge pickup completely, keeping the existing wiring/pots as it is (largely). Isolating it that way, I'll get the best Precision sound out of this bass, right?

Any other suggestions? Wiring diagram greatly appreciated too... I'm handy with a solder iron, but I often make mistakes when designing the wiring myself

 

[Bourbongangster]

Take a look at the link below. I think this might point you in the right direction.

P/J Wiring Question

 

[mcnach]

Take a look at the link below. I think this might point you in the right direction.

P/J Wiring Question

Thanks!

I was originally thinking of a bypass switch for the bridge (pickup + volume control)... but I'm starting to think that a VVT *plus* pickup switch (as found in many basses) may be a better choice? Hmmm.

 

[Bourbongangster]

Thanks!

I was originally thinking of a bypass switch for the bridge (pickup + volume control)... but I'm starting to think that a VVT *plus* pickup switch (as found in many basses) may be a better choice? Hmmm.

Not a bad idea. In fact I have that setup on a parts bass I put together, but I'm not crazy about it TBH. Having the two volumes doesn't really add much benefit with a three-way switch. It just doesn't blend very well in the middle position so if I was considering doing that setup again, I would just skip the second volume altogether and just wire it up like a Mustang P/J.

 

[mcnach]

Not a bad idea. In fact I have that setup on a parts bass I put together, but I'm not crazy about it TBH. Having the two volumes doesn't really add much benefit with a three-way switch. It just doesn't blend very well in the middle position so if I was considering doing that setup again, I would just skip the second volume altogether and just wire it up like a Mustang P/J.

That is attractive as I like simple controls... If you give me many options I get distracted trying to use them all

However, I do like that tone you get with the P full on and the J *just* engaging, but distinct from a full P+J, that you get when you back off the J volume *just* a bit...

I rarely use the bridge pickup alone... so with a VVT + switch you kind of "save your preset" and then use the switch to select between full P and "whatever mix"...
Then again, I can probably achieve a similar tone by screwing the bridge pickup further into the body, weakening its sound... but then I really never will use the bridge alone.

Choices, choices!!!
There's a reason I generally go for single pickup basses

 

[RobbieK]

When I use only the P pickup, the sound is noticeably affected by using the split coil switch, sounding a lot more "Precision" when in single coil mode, even if the JJ volume is off completely

So you are saying that when the jj vol is turned all the way down and the P vol all the way up, the jj split coil switch effects the tone? If this is the case, there's a problem with the wiring.

 

[Kikegg]

I've got a PJ, well...actually a P/JJ, where the bridge pickup is a dual J wired as a humbucker.

Wiring is VVT.

The JJ can be split to give a single coil alone, with a pull/push switch located on the tone control.

When I use only the P pickup, the sound is noticeably affected by using the split coil switch, sounding a lot more "Precision" when in single coil mode, even if the JJ volume is off completely.

I'm thinking I'd like to install a mini switch that bypasses the bridge pickup completely, keeping the existing wiring/pots as it is (largely). Isolating it that way, I'll get the best Precision sound out of this bass, right?

Any other suggestions? Wiring diagram greatly appreciated too... I'm handy with a solder iron, but I often make mistakes when designing the wiring myself

For what I understand, you may want a Tony Franklin alike wiring to get the J(JJ) pickup completely out of the circuit. Actually this wiring is Master Volume, 3-way switch (P alone, PJ or J alone) and Master Tone. I don't know if the push-pull tone would be kept from your current wiring or not as-is.

Check this thread: Tony Franklin bass schematic

 

[mcnach]

So you are saying that when the jj vol is turned all the way down and the P vol all the way up, the jj split coil switch effects the tone? If this is the case, there's a problem with the wiring.

Yes, that's what I say.

No, there's no problem with the wiring.

The bridge pickup AND its potentiometer are still in the circuit, and they affect the tone of the P pickup (it darkens the tone and to my ears the upper mids are affected). I'm not an electronics guy (I am very good at soldering, but that's all), so I can't explain technically what the effect is called, but it's a well known effect, and the reason for people saying a PJ bass cannot do a 'real' P sound. It's subtle, but it is there...
There is a difference in a normal PJ when you remove the J entirely (with a switch, bypassing the J). In my case I add/remove a pickup (JJ or single J), and that's noticeable. The P sounds more the way I want it to sound when there's just the bridge pot plus 1x J pickup, compared to bridge pot plus 2x J pickups.

It is not a HUGE effect... you still recognise it as a Precision, but removing the bridge pickup and associated volume controls from the circuit completely gives the P pickup a little extra that (to my ears) feels just right. It's a simple and cheap mod too.

 

[Kikegg]

That's the same I feel with my PJ, currently with the EMG GZR PJ set. You get the Precision vibe but different. I'm waiting for the solderless items to rewire it this way

 

[mcnach]

That's the same I feel with my PJ, currently with the EMG GZR PJ set. You get the Precision vibe but different. I'm waiting for the solderless items to rewire it this way

I've only tried the GZR P alone once, really cool pickup.

edit: me encanta tu avatar

 

[Kikegg]

I've only tried the GZR P alone once, really cool pickup.

edit: me encanta tu avatar

Me alegra que te guste. Glad you like it. A young girl put the Republican flag in the Cibeles statue, here in Madrid, some years ago during a general strike rally. I could take that shot and it's my avatar since then.

 

[RobbieK]

Yes, that's what I say.

No, there's no problem with the wiring.

If flicking the switch effects the tone when J pickup is all the way down, I think you may have a faulty pot or some problem with the wiring. I'm not being a jerk here, I don't mean anything weird or personal. Perhaps you could post the wiring diagram that was used. With a VVT, the hot wires from the pickups are connected to the wipers of the volume pots, so when the pot is all the way down, both sides of the pickup and its associated switch should be earthed - effectively out of the circuit.

The slight dulling of the solo P tone you get with a VVT PJ is actually due to the slight extra loading of the J's vol pot, not the pickup. And that's easy to remedy. There's several ways. But I think it's a good idea to get to the bottom of why the switch is still doing something when it shouldn't.

 

[mcnach]

If flicking the switch effects the tone when J pickup is all the way down, I think you may have a faulty pot or some problem with the wiring. I'm not being a jerk here, I don't mean anything weird or personal. Perhaps you could post the wiring diagram that was used. With a VVT, the hot wires from the pickups are connected to the wipers of the volume pots, so when the pot is all the way down, both sides of the pickup and its associated switch should be earthed - effectively out of the circuit.

The slight dulling of the solo P tone you get with a VVT PJ is actually due to the slight extra loading of the J's vol pot, not the pickup. And that's easy to remedy. There's several ways. But I think it's a good idea to get to the bottom of why the switch is still doing something when it shouldn't.

Oh, I thought BOTH the pot and the pickup were having an effect, unless isolated (grounded, I guess) using a switch.
Maybe the push/pull switch still has an effect through the tone control? (I really don't know )

It's the original factory wiring (Maruszczyk Jake). I'll probably just lift the whole wiring as is and keep it in case I want to return it to original quickly, and buy new pots to wire the thing fresh, as it's pretty cheap. I'll take off the pickguard this weekend and take a picture of the wiring. I'll post it here.
If you feel like it and want to have a look and see if there's anything obviously strange... I'll leave a virtual cold beer here

 

[RobbieK]

Nice one. Those a good basses. The Australian agent for Maruszczyk is a mate of mine, and I've played quite a few of them.

That switch is a funny one. Perhaps it is wired in a way I haven't seen or thought of... not sure. With the J vol down to zero, it really should be shorted to earth like the pickup...

But yeah, the quirk of VVT wiring is that the vol pots are wired the wrong way around (kind of), unlike any other volume pot not just in basses, but in amps, hifi, pedals, etc etc. This I'm guessing was Leo Fender's idea and it is actually quite a creative solution to improve the Jazz bass circuit. (The original 60's VTVT circuit was far from ideal.)

Anyway, a P bass with tone and vol both dimmed has the pickup "seeing" two 250k resistors in parallel across the signal. So the trick with getting a PJ to truly sound like a P when the J is turned right down, is to have the same load. IOW one that totals 125K. Really, the easiest way to do this is simply to replace the tone pot with a no-load pot. This is a pot with a cut in its track so that the resistance of the pot is infinite when it is dimed. This way, with the J on zero and the P and Tone pots dimed, the P is "seeing" the load of both the volume pots, but not the tone pot. And this will total 125K.

This sounds counter-intuitive I know, but if you translate the wiregrams to actual electronics schematics, it is easy to understand.

 

[mcnach]

Nice one. Those a good basses. The Australian agent for Maruszczyk is a mate of mine, and I've played quite a few of them.

That switch is a funny one. Perhaps it is wired in a way I haven't seen or thought of... not sure. With the J vol down to zero, it really should be shorted to earth like the pickup...

But yeah, the quirk of VVT wiring is that the vol pots are wired the wrong way around (kind of), unlike any other volume pot not just in basses, but in amps, hifi, pedals, etc etc. This I'm guessing was Leo Fender's idea and it is actually quite a creative solution to improve the Jazz bass circuit. (The original 60's VTVT circuit was far from ideal.)

Anyway, a P bass with tone and vol both dimmed has the pickup "seeing" two 250k resistors in parallel across the signal. So the trick with getting a PJ to truly sound like a P when the J is turned right down, is to have the same load. IOW one that totals 125K. Really, the easiest way to do this is simply to replace the tone pot with a no-load pot. This is a pot with a cut in its track so that the resistance of the pot is infinite when it is dimed. This way, with the J on zero and the P and Tone pots dimed, the P is "seeing" the load of both the volume pots, but not the tone pot. And this will total 125K.

This sounds counter-intuitive I know, but if you translate the wiregrams to actual electronics schematics, it is easy to understand.

I don't like you. You're making me think of more options.
Kidding...
Thank you for taking the time to explain these things a little!

I need to get my head around this... pen and paper time. I'm used to just 'colour by numbers' without knowing really what the wiring does, just soldering as I'm told... Maybe it's time to put a little more effort, so that I choose the wiring I want and don't have to come back to change things later...

I haven't opened up the bass yet, busy day. They make some really nice basses. This is my first one (I've owned 3, but I sold one on). I heard good things about them and I liked the idea of a P/JJ at the time, so I ordered one with their standard configuration, except for the neck, which I specified the dimensions of and had it lacquered glossy. You get a lot of bass for your money with Maruszczyk. My only complaints are with regards to the hardware. The screws they use are made of an alloy of steel with 80% cheese in it. Really soft metal, very hard to strip the heads of the screws. I had one pickup screw that seemed stuck... and eventually it started to give in... very carefully to avoid slipping I kept applying force and the screw kept turning... only it wasn't turning: I was shearing it! it finally broke off. I had some fun fixing that one.

Here's the P/JJ:

 

[mcnach]

The basses I've seen with VVT + 3-way pickup switch... that will still isolate the P pickup, right?

I have a bass with that configuration (using two MM style pickups) and I like it. If that would do what I'm after, I might just copy that. Coil-tap for the JJ optional: I am not that bothered, really, I like the fatter tones of the full pickup when alone or blended.

 

[RobbieK]

I need to get my head around this... pen and paper time. I'm used to just 'colour by numbers' without knowing really what the wiring does, just soldering as I'm told... Maybe it's time to put a little more effort, so that I choose the wiring I want and don't have to come back to change things later...

This comes up a lot, so I thought I'd put some schematics together...

Believe it or not, the cap is essentially a short when the tone pot is dimed. So that means you can think of the tone pot as a simple resistance in parallel with the other pot(s).

If you follow the left column down, you are left with the P essentially "seeing" a 125K resistor.

Follow the middle column down, and the J is out of the circuit because both ends of its coil are earthed. But its volume pot is still there, reducing the P's load resistor down to 83K. And you are right. There is an audible difference here. If you set up a test rig, and switch a solo P pickup between 125K and 83K, you can hear a little bit of treble being dulled. You are right, it's subtle, but definitely audible.

So with a no-load tone pot maxed, the final resistance for the solo P is back to 125K.

Simple! (If you are used to reading electronics schematics that is lol...)

You should know that the quirky vol pot wiring for the PJ (and jazz bass, and really any passive VVT) is good in one way (kicking the J out of the circuit when all the way down), but bad in another way. It will roll more treble off when you start to turn it down than with a regular (single pickup) P bass circuit. This is because the resistance between the hot side of the coil and earth gets less and less when the pickup is wired to the wiper. But let's face it, most of us play with the vol pot dimed...

If you are interested more about how these simple passive circuits work, I have two-part video about this. Part 1 and Invalid Link Removed.

 

[RobbieK]

The screws they use are made of an alloy of steel with 80% cheese in it. Really soft metal,

Yeah, I have a lot of different sized philips head screwdrivers, and now even a couple of JIS screwdrivers. I talk a bit about this in Invalid Link Removedvideo. Not sure why a new bass would be such trouble. FWIW, I like to use a little smear of lanolin grease on pickup screws to stop them from rusting and to make it easier to shift them down the track...

The basses I've seen with VVT + 3-way pickup switch... that will still isolate the P pickup, right?

Yep, it should do.

 

[bdplaid]

The slight dulling of the solo P tone you get with a VVT PJ is actually due to the slight extra loading of the J's vol pot, not the pickup. And that's easy to remedy. There's several ways.

Resurrecting the thread... Good info and I like your vids. But I'm looking for a schematic for killing the pot and pickup on a PJ with VVT. As with others, I'm looking for the pure P tone, but don't want to use a no-load to do it. I'm planning to use a push/pull pot.

Thanks!

 

[Crater]

The wire at the red arrow is the one needs to be cut and have switch wired in. "open" for no J pickup, closed to have the J pickup connected as normal. Since the P pickups volume control is always connected, there shouldn't be any issues with pops or hum when the switch is activated.