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Wiring harness for J/P/J

Thumper

Thumper

Supporting Member
Mar 22, 2000
5,272
10,997
74
Syracuse Ut
#1
JPJ strung 3 (480x640).jpg

I have a J/P/J (Lollar PUPs) which was put together by a studio musician so that he could have a J or P on call. It has 2 separate output jacks as each system has it's own separate circuit. There is no tone control or blend which I want to correct so I can change on the fly. I had another TBer generously provide a design, he is ok with me providing it here for review, so I can be sure it can't be improved upon before I have it built.

PerformerStealthJPJS-PB-3-V-T.png
 
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#2
After looking at this (I am not electronically inclined), does DPDT mean double pole double throw or ?

Is it 3 knobs and 2 toggles?

I would be inclined to use an audio taper volume switch unless there is a valid reason not to.

The diagram author stated he used 500 pots due to the number of PUPS, I thought they were intended for active systems and 250s for passive?

Will this setup require drilling more holes in my pickguard?

I am inclined to spec a .o47mf, is there a compelling reason to use another value!

Stealth, feel free to weigh in!
 
#3
Thumper said:
does DPDT mean double pole double throw
Click to expand...
Yes.
Thumper said:
Is it 3 knobs and 2 toggles?
Click to expand...
Yes.
Thumper said:
The diagram author stated he used 500 pots due to the number of PUPS, I thought they were intended for active systems and 250s for passive?
Click to expand...
Nope, incorrect. The volume control on an active system, IF the volume control is after the preamp, is typically 25K ohms. Both 250K and 500K pots are appropriate for passive basses; 500K ohms will give a little more brightness and output vs. 250K pots. It's really just a personal choice, either value should work fine.
Thumper said:
I am inclined to spec a .o47mf, is there a compelling reason to use another value!
Click to expand...
Again, this is largely a personal choice. The 0.047 is the standard value for passive tone controls, a 0.022 will be a little brighter when the tone is rolled all the way down. Probably little to no difference when the control is all the way up.
 
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#4
I gig with a country band, jam classic rock. Either way, I'm not into highs, generally run my tone rolled off 3/4 (clockwise, or does that mean I roll the tone on?) more on my Pbasses. So this harness should reflect that preference. Thanks for the input.
 
#5
Just to pipe in on the subject again, Crater explained it exactly as I would. I listed 500 kOhm and .047 uF because I know I wanted a brighter sound out of it from the get-go, but also because having too many coils active at the same time leads to a less bright tone, so the 500 kOhm pots offset that.

Crater, one of the things that I need a bit of verification on is the blend pot in series mode - is it going to work as I explained in the bottom-left diagram, or did I miss something?
 
#6
Stealth said:
Crater, one of the things that I need a bit of verification on is the blend pot in series mode - is it going to work as I explained in the bottom-left diagram, or did I miss something?
Click to expand...
In series mode one side of the blend pot will act as a series resistance, the other side of the blend is disconnected. So no difference from the blend pot being in middle position to being rolled to the neck pickup, but as the blend pot is rolled to the bridge pickup side, there will be increasing series resistance to a max of 250K ohm with the pot all the way to the bridge side.

I had to convert your pictorial diagram into a schematic, that's the only way my brain can figure it out. o_O

schemeit-project_zpsjha3fgko-1.gif


L1 is the neck jazz pickup, L2 is the bridge jazz pickup, L3 is the 'middle' P-bass pickup, S2 is the series/parallel swtich, S3/S4 is the pickup selector, R3 is the master volume, R4 is the tone control and J1 is the output jack. These are drawn using an on-line program, so excuse their thrown-together appearance. The unmarked pots is the MN dual-gang blend pot.
 
#9
I know it's been a minute since this thread has been touched but, which DPDT is the series/parallel and which is the pickup selector? I imagine it's the top and bottom, respectively, but I'm not super adept with wiring and the electronics, so if someone could shed some light for me, it would be much appreciated.
 
#11
The top DPDT (on-on with the top two pins connected) is series-parallel for the Jazz pickups. The bottom DPDT (on-on-on with the middle pins connected) is the pickup selector. All ground symbols must be connected, so they all have to end up at the jack's ground lug.
 
#14
Think in terms of continuity, flow of the connection. All pots need to be grounded, although in some cases the blend pot does not get grounded. There are many ideas and opinions about grounding, but I always think in terms of flow. That is to say, there needs to be a ground connection that connects all pieces to that ground lug on the jack. I simply run a ground wire along all pots, from pot to pot, leading eventually to the jack. The bridge ground also needs to be somewhere in the chain.

The toggle switch does not need to be grounded.

The particular pot that you choose to ground to does not matter, imo, although some on this board will disagree. So your bridge ground wire can go any pot as long as all pots are grounded together, like a train. if you go to my thread on harnesses I sell, you can see the linear connection of the ground wires. or simply open up your bass and take a look at it's harness. I usually try to spread out the ground connections so that any one pot does not get too crowded. Finally, you can test your ground connections witha multi-meter. put one connector of the meter on the last pot, and the other on the ground terminal on the jack. The resistance should read zero. Touch one meter connector to the bridge, and another to the jack nut (you can do this without taking the bass apart, of course) and you should also read zero resistance.

The only other thing to keep in mind is that if your bass is shielded, the shielding needs to be connected somehow to the ground wires. There are several options for that as well.

Search the forum, that is how I learned everything I know about grounding and wiring.
 
#15
So if I ran the series/parallel ground wire and the P pup ground wire to the volume pot, ran the bridge J pup ground wire and the jack ground wire to the tone pot, ran a wire between the two pots, and had a wire going from one of them to the bridge, it would be all good?
 
#16
I hope to have a report on this bass soon, gotta get through the first gig with a new drummer on Saturday and taxes on Monday first. I have to do some routing under the DPDT switch, the P body routing gets deep just South of that spot.
 

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