Question about wiring a PJ bass...

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FunkyJase
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Question about wiring a PJ bass...

Post by FunkyJase » 02 Feb 2018, 19:03

It might be a dumb question but...
Can you wire a PJ bass to be Vol/vol/tone but the tone control ONLY works on the split P pickup? So the jazz bridge pickup would not be effected by any tone cap at all...
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narcdor
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Re: Question about wiring a PJ bass...

Post by narcdor » 02 Feb 2018, 20:13

Edit: made no sense when I read over my own drivrl
Last edited by narcdor on 02 Feb 2018, 20:22, edited 1 time in total.
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Re: Question about wiring a PJ bass...

Post by narcdor » 02 Feb 2018, 20:19

Hmm taking some cues from a Les Paul which has independent tone pots for each pickup you should be able to wire the P tone pot out of direct line with the J pot and use it more like a tone bleed.

J goes to V then jack. P goes to V and both to T bleed to ground as well as to jack.

Picture probably says it better hey
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Re: Question about wiring a PJ bass...

Post by packrat » 02 Feb 2018, 20:23

https://support.fender.com/hc/en-us/art ... e-Diagrams

If you look at a 62 jazz diagram at that link you’ll see vol/tone vol/tone. If you leave out the second tone pot you’ll get something which *mostly* has tone on only one pickup, but as per discussions about stacked jazz, there will be some effects.

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Bill Fitzmaurice
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Re: Question about wiring a PJ bass...

Post by Bill Fitzmaurice » 02 Feb 2018, 23:14

With passives you can't totally isolate the tone control effect to one pickup. With the volume controls at full a tone control on either pickup is fully in circuit for both. There is separation when the volume controls aren't at full, the degree of separation increasing as the volume is reduced, but unless they're turned way down the one tone control will still affect both pickups.

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Re: Question about wiring a PJ bass...

Post by david1234 » 03 Feb 2018, 10:13

What Bill said is the case (as usual!).

To drop treble from the P only with little impact on the J, there are a few really odd options you could try like an inductor in series with the P; also mucking about with capacitors on just one half of the P (though I can't see how this wouldn't impact the hum cancelling). There's probably a reason these are not often done though!

Another tidier way is to use an active buffer before the blend, such as this guy: https://www.bestbassgear.com/bartolini- ... db-918.htm

It happens to have the advantage of being able to put a little bit of extra gain on your J if you need it, too. The active buffer eliminates the interaction between the pickups, for example that volume drop that you get on a PJ by having both pickups on full.
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Re: Question about wiring a PJ bass...

Post by NotTheFish » 03 Feb 2018, 10:26

What about a stacked J bass type harness ?

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Re: Question about wiring a PJ bass...

Post by packrat » 03 Feb 2018, 10:29

NotTheFish wrote:
03 Feb 2018, 10:26
What about a stacked J bass type harness ?
It turns out that's only _mostly_ independent[1]. (I hinted at this upthread) for the reasons explained. If you think about the tone pot as a dialed-in high frequency bypass shunt (whatever floats your boat, really) it's clear why that happens given everything is all connected.

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[1] Not really even mostly, to be honest.

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Re: Question about wiring a PJ bass...

Post by NotTheFish » 03 Feb 2018, 10:53

Ok.. Thanks packrat..

Funky: I too have a set of PJ pickups from Greg and I have this preamp in that bass - http://www.acguitars.co.uk/acg-eq01-filter-pre-amp/

This allows some interesting tone controlling of each pickup. One of the many sounds I like is to roll the filter freq for the P back a little (rolls the treble off) and then boost that cutoff freq while running the J open. This preamp is filter bases like a Wals.

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Re: Question about wiring a PJ bass...

Post by Bill Fitzmaurice » 03 Feb 2018, 13:15

NotTheFish wrote:
03 Feb 2018, 10:26
What about a stacked J bass type harness ?
All that does is to place the pots back to back instead of side by side, they still function the same way. An active pre is the only way to get it to work the way the OP wants, something I haven't done without since I made my first circa 1973.

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Re: Question about wiring a PJ bass...

Post by FunkyJase » 04 Feb 2018, 08:13

Right. So it's a LOT more complicated than expected he he
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Re: Question about wiring a PJ bass...

Post by david1234 » 04 Feb 2018, 08:44

Yes!

I have deliberately wired a tone pot to the bridge J on a JJ bass I have, so it tames the bridge when bridge is favoured and has little impact when the neck is favoured. This is because I tend to prefer the sound of the zingy treble that comes from its neck J than the bitey treble that comes off the bridge J. It's wired VBT mind you.
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Re: Question about wiring a PJ bass...

Post by bassbass » 04 Feb 2018, 11:04

I've experimented a lot with this idea over the years.

Firstly, if you isolate the pickups by whatever means, then combine their signals, it's actually very hard to hear which has had its treble rolled down. You usually need to tap both with a metal object. OTOH, if you have a blend pot, and you want to quickly go from say dark tone-down bridge pickup to bright open-tone neck pickup by moving just one knob, then isolating the pickups and having separate tone pots is useful I guess.

Anyway, it's really best to do this with an active circuit. In fact a very simple 1 opamp active mixing circuit would work for this, and fwiw, also remove the interactions that happen with the two vol pots. Or as other's have mentioned, a couple of simple buffers would work as well.

As for doing this stuff passively, well yes, if you use a pair of resistors to sum the signals, then this creates isolation to a degree. With a typical pair of J pickups, a pair of 15k resistors will isolate them enough that if you just roll off a bit of treble on one pickup, the other won't be effected by much at all. And these resistors won't reduce the output of the bass by any audible amount. However, that bright scooped tone you get with a jazz bass when both pickups are maxed will start to disappear. Of couse, one guy's treble is another guy's upper mids. ;) How bright your strings and speakers are will govern how much of this treble loss is acceptable to you.

OTOH, if you want to really roll the tone off a lot, past halfway down say, well the resistors required for any real isolation would really start to reduce the overall output and tone of the bass. (The original 60's jazz bass VTVT circuit is an example of this.)

Further more, if you expect to have the tone pot rolled down to zero on one pickup where the cap causes that little mid hump sound, well it's not realistically possible to isolate this from the other pickup with a simple passive circuit.
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Re: Question about wiring a PJ bass...

Post by FunkyJase » 05 Feb 2018, 08:01

Yeah bummer - Oh well :-)
'twas just an idea.
Im thinking I should just embrace the P bass and stop trying to find the perfect PJ.
Aphekgregs pickups are spectacular but I always want more more more he he
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Re: Question about wiring a PJ bass...

Post by bassbass » 05 Feb 2018, 11:44

Well... I didn't say it was impossible. Instead of a wire where the two vol pots are joined, try a couple of 15k or 22k resistors, with their junction running to the jack. Then move the wire to the tone pot over to the wiper of the P pickup vol. This will give you some isolation. A couple of resistors cost 50c from jaycar.

Don't ever be put off. You should always have a go at wiring something cool. If it doesn't work out, you've still learnt something man.

I have a PJ wiring that I think is really nice. FWIW, an under wound alnico P (my own wind, 8k in series), and a (hot, mid-rangey) 80's Dimarzio hum-cancelling J. For blend I use a 200K A/C Pot that is not earthed. It also has a high-low z/pre-post vol pot.

The only thing I'd change is I'd prefer the J was further from the bridge. My 80's JB4 has the J in the 70's possy. I believe the reissues have it ffurther from the bridge...
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