An idea for wiring P+J

Discussion in 'Pickups & Electronics [BG]' started by Andrew_squierPJ, Oct 11, 2012.


  1. Andrew_squierPJ

    Andrew_squierPJ

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    I have decided to add a Jazz bridge pickup to my Squier Precision. I'm a great one for research which is what brought me to this forum.

    In my cyber travels I found a template and router bits on Stewmac, how to shield and ground everything etc etc, but I also found something which really caught my interest... concentric (stacked) 250/500k pots. In my mind I thought it would be possible to stay with the existing 3 holes - volume, treble, jack - of the precision, but by using concentric pots, have a separate volume and tone control for each pickup.

    I don't want to clutter up the bass with any switches, but I would like to be able to isolate each pickup just by turning the volume down on the other one, or dialling them up separately to get a blend for certain songs.

    I've searched the forum but can't find a definitive answer on whether this is possible. For example, would one pair of pots need to act as volumes and one pair for tones, or would the individual stacked pairs have to act as a volume/tone for each separate pickup? hope the wording of my question is not too ambiguous. I've been all over the internet searching for diagrams but nothing seems to cover using stacked concentric pots in this way.

    I am keen to take photos and make comments as the project progresses from routing to shielding to wiring and so forth, because I think the concept visually has very tidy looking potential not to mention the improvement in frequency control.

    I should add that electronics is not my forte but as they say have soldering iron will travel.
     
  2. Nev375

    Nev375

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    Yes, it's quite possible, the old jazz basses came with stacked pots as you describe.

    Having two tone controls typically causes some interaction between them that fender dealt with by adding a resistor to lessen the effect. I would recommend Stacked volume and a single master tone control.

    Another idea would be to use the concentric pot as a stacked Master vol/tone and get a dual pot with a center detente and wire as a pan pot to isolate blend the two pickups together.
     
  3. Andrew_squierPJ

    Andrew_squierPJ

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    Thanks Nev, I'll be starting the project when all the parts arrive, and I'm guessing some experimentation will be on the cards when it comes to wiring. I will order an extra single pot for master tone if that's how to get it working.

    I have a friend who understands electronic values (resistors, pots, etc) so we may be able to come up with something. Either way I will post my findings here with photos hopefully. If it turns out that I can run separate tones for each pickup, I will certainly try to draw a circuit diagram (with the help of my electronics friend).

    Just sharing the idea here is getting me real excited about the project, so glad I found this forum.
     
  4. FunkMetalBass

    FunkMetalBass

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    There are a million wiring diagrams out there for P's, J's, and ever P-J's. The only thing you have to do is stack the volume pot wiring (the concentric pots are just two separate potentiometers attached concentrically, with the bottom pot attached to the top knob, and the top pot attached to the bottom knob).
     
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  6. line6man

    line6man

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    The values are not critical, and are typically determined by tradition. Fender used 220k resistors, 250k pots and 0.047uF caps.

    If you are going to isolate the signals with resistors, be advised that that will cost you output/treble. There is a reason that Fender abandoned that wiring scheme a long time ago.
     
  7. Andrew_squierPJ

    Andrew_squierPJ

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    Thanks for the heads up. To be honest, the idea for dual concentrics came out of a desire for keeping the bass uncluttered and not having to rout and drill to add a pot, as in Oteil Burbridge's PJ conversion:

    [​IMG]

    Plus I really like the look of the stacked knobs:

    [​IMG]
     
  8. Andrew_squierPJ

    Andrew_squierPJ

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    It's been more than 3 months but I finally finished the bass... well not quite finished because I didn't realise that the genuine Fender dual pot didn't come with a washer and nut :rollno: so when I finally opened the packet I realised just how lame my powers of observation are. I had it sitting on the shelf unopened in a plastic bag with the Fender folded card stapled on top, must have looked at it a thousand times and still it didn't dawn on me. Why the hell would Fender supply pots without nuts? So until the spare nut and washer arrives I have the pot held in with a small zip tie.

    I had another problem too... I ordered a pair of generic knobs thinking they're all the same, but they were too small, so I tried to drill them out, but the drill bit drifted into the lock screw channel and went out of round (I don't have a drill press). I ordered another pair which I thought must fit because the advert (eBay) said "suits Fender concentric pots", but guess what? These ones are too bloody big :bawl:

    I had intended to photograph every step of the way, but got so caught up I forgot a lot of detail. Here are the photos I took:

    Some original pics: (I just discovered 2 only per post... more to come)
     

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  9. Andrew_squierPJ

    Andrew_squierPJ

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    Here you'll notice some scratches near where I will rout. They really annoy me so I decided to make a pup ring from some brass sheet to hide them.

    I read in another thread where someone said "There are no Fenders made in China"... Well according to the sticker on my bass, there are.
     

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  10. Andrew_squierPJ

    Andrew_squierPJ

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    Stripped.

    The wiring is pretty basic on these models. Check out the dirty long earth strap, I hate it, in fact I hate pots with solder on the back, full stop. I reckon it's plain ugly and kinda lazy too.
     

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  11. DWBass

    DWBass The Funkfather Supporting Member

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    I did the same thing with my P-Bass. I added a Jazz pickup (both are active EMG's) I added an EMG stacked dual volume pot in the first position and added a BTC (stacked bass/treble) in the second position.
     
  12. Andrew_squierPJ

    Andrew_squierPJ

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    Using the template I pencilled in the outline and then freehand routed with a 1/2 inch bit progressively to depth, about a 1/4 inch each pass.

    I put the template in place and routed out with the 3/8 bit. On the final pass I broke the cardinal rule of routing... never withdraw the router until it stops spinning... the bloody thing bit into the wood and my expensive template. Oh well, it just confirmed my decision to make a pickup ring.
     

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  13. Andrew_squierPJ

    Andrew_squierPJ

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    The P-pickups are fairly crappy with plastic bobbins, and the Jazz is a genuine Fender spare part made in Mexico, also in plastic bobbins. I might upgrade later but for now just happy to have the bass up and running again.

    While researching the project I discovered that shielding is the new black. I have to admit it was damn hard getting the tape in so it looked beautiful, but it was perhaps the most rewarding stage.
     

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  14. Andrew_squierPJ

    Andrew_squierPJ

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    Next I added a strip of copper tape at the rear edge of the bridge so the earth wire would be sandwiched for a better contact. Upon reflection I used an off-cut on the front edge to balance it up.

    Upon further reflection, I added more copper tape to where the pup ring would sit, with overhang to fold down into the cavity - apparently the adhesive backing is conductive - which in theory would make the ring itself a shield as well.
     

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  15. Andrew_squierPJ

    Andrew_squierPJ

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    Fender was kind enough to include a screw lug in-line on the earth wire, which saved a minor headache. I drilled the hole with a 5mm spade bit on a driver extension to keep the angle nice and low.
     

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  16. bassdude51

    bassdude51 Supporting Member

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    I put together a P bass with an added J bridge pickup and went with the dual concentric pots and knobs and it turned out great and I didn't have to butcher or even change the control cavity.

    I'd post photos but don't have any in the PC at the moment.

    One suggestion for your project.

    Skip the tone control and go with 2 volumes. Most of the time we bassists hardly ever use the tone control on a passive bass.

    With 2 volumes and no tone you're good to go and you won't have to change the control cavity.

    For routing your J cavity. You can simply trace the plastic pickup cover onto a piece of paper, cut it out with sissors and use it for a template on your bass body. Find the center line of the bass body. Use the center screw hole of the bridge and measure for the center of the neck cavity. You can use masking tape to mark off center line, etc.

    I've used a router free hand for the pickup cavity. It's very, very, very scary but go at a snail's pace.

    For the final cut for the pickup cavity hole, I use strips of sand paper stuck onto a flat surface of a chisel or something with double stick scotch tape to shape up a perfect hole.

    Be prepared for the fact that by going free hand you could very well do some terrible damage to your bass body.

    Practice on scrap wood.

    You could probably make a pickup cavity with an electric drill by make many, many holes and then chisel them out.

    I skipped many details but remember........."necessity is the mother of invention". You'll figure it out.
     
  17. Andrew_squierPJ

    Andrew_squierPJ

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    Next I realised I didn't have any sponge for the new pickup, so I cut a piece from each of the P's, which will sit one each end of the J.

    Cutting and shaping the pup ring was fairly intense but also very rewarding... forgot to take any photos.

    By this stage I was well into the wiring before I remembered to take more photos.
     

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  18. bassdude51

    bassdude51 Supporting Member

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    Photos of dual concentric pots and knobs and DIY J cavity rout cut (freehand).

    (If I were you, I'd still consider skipping a tone control and going 2 volumes.)

    [​IMG]

    [​IMG]
     
  19. Andrew_squierPJ

    Andrew_squierPJ

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    Neither did I, instead used 1 x 250/500 concentric pot and 1 x 250 k tone pot with .047 uF capacitor.

    Awesome idea! Thanks man... I am so p'd off trying to get knobs that fit I'm just about tearing my hair out. I'm pretty sure (thanks to your suggestion) now that I will get CTS 1 x 250k (P) and 1 x 500k (J) pots and set it up just as you said... "We Bassists" I LOVE it Bassdude!

    Next I soldered earth wires to the copper tape to activate the shielding. I was worried it would burn through but it was really easy, stuck like s**t to a blanket.
     

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  20. Bassamatic

    Bassamatic keepin' the beat since the 60's

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    That is VERY nicely done. Enjoy!

    Just want to add when I have added a pickup, I moved the output jack to the side of the bass with the metal mounting plate. Not only leaves the 3 holes for pots, but it is much stronger than mounting on the pickguard.
     
  21. Andrew_squierPJ

    Andrew_squierPJ

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    I just realised that I've almost used up all my upload allowance so I better stop for now. It's late here on the east coast of Oz, so I will come back to the thread tomorrow and see if I can't shrink all the photos to half size then replace them here. Be a shame to get this far and not show the finished product.

    I did not solder any pots but instead used solder lugs on the threaded part of the pots to earth them, and used heat shrink to insulate all hot terminals.

    Before I did this conversion, my little Chinese P-bass was as noisy as all hell, but with all the shielding and earth-overkill, my P-J is now DEAD SILENT. I mean zero noise, almost unbelievable. When I tested the wiring without strings, I plugged in the lead and turned on the amp and I was momentarily crestfallen, thinking I had somehow failed on the wiring, it was so silent. The disappointment was short-lived because next I touched a screw driver the the pole pieces and I have to say the moment was up there with some of the most memorable experiences of my life... they both made tapping sounds in the amp.

    I thought maybe when I strung her up the strings would attract noise, but nope, this bass is absolutely NOISE-FREE!

    I just reduced this pic to 75% in office picture manager and managed to squeeze it in. The finished product... well when I get a nut and washer for the dual concentric (instead of the zip tie) and some knobs... or better still consign the dual to the spare parts bin and go with Bassdude's idea of 2 volumes NO tone.

    I'm also thinking all that white looks kind of stark, and that maybe a black pearl pickguard might look better.

    P.S. I also took off the neck, straightened it out without load, marked all the frets with black texta and laid a sanding beam on them. No wonder there was fret buzz and such a high action, they were up and down like a dunny seat at a party. Anyway, got 'em all level, dressed 'em with a fret file finished with 2,000 emery paper, loaded up the strings and straightened up the neck again. Fret #1 was .020", and I set #12 at .060", did the intonation and she plays like a brand new bass. I'm as happy as a pig in s**t.
     

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