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Di Marzio Model J


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Hi guys,

I am the lucky owner of a new set of a Model J black set (DP247+DP248). I am customizing a MIJ jazz bass, upgrading several components (I will post pics and info later on once I am sure everything is done well :))

I have installed them following the official instructions, using the "parallel configuration" (https://d2emr0qhzqfj88.cloudfront.net/s3fs-public/diagrams/DiMarzio Area J Wiring Diagram_0.pdf)

However I have a couple of doubts:
1) for simplicity's sake, I connected the ground cable (coming from the copper tab under the bridge) directly to the first volume pot (third contact, together with the blackearth cable), instead of soldering it to the jack contact. Is this OK or is it a mistake? in theory all the earth contacts should be at the same potential and it should not make any difference whether a connection is made at a point A or B...

2) once the connection phase was completed, I tested everything. the sound comes out well without any problems. However, I am not convinced by the way the sound comes out from the parallel between the two pots: if I set them to "max" individually, everything goes smoothly. But if I turn them both on, the output level drops drastically (I'd say, by ear, more than half the volume of a single pickup). Moreover, the mixing is not balanced and uniform, the bridge pickup can be heard less than the neck one and it starts to be heard only when the pot is at 90%, first the sound remains practically unchanged and then it suddenly grows. Is this normal on a passive bass?

Do you have any tips and/or advice on this?

Thanks, cheers!

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If the pickups are wired exactly as indicated, they shouldn't be out of phase...

Maybe your neck pickup is way too close to the strings... or the bridge way too far.

Concerning the fact that you only hear output changes on the remaining 10% of your pot, it's normal as your pots are logarithmic ones. If you want to hear a better progression, put some linear pots instead.

Nothing wrong with the way you made the grounding. To be sure just check the grounding continuity.

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When you say 'all is smooth' for each individually on max - are they around about the same volume as each other on max?

As @Hellzero says, the two pickups need to be balanced volume-wise (done by adjusting the pickup heights) otherwise when you feed in the two together, the volume will tend to drop as the higher output p/u is impacted by the lower one.

Usually, the gap between the top of the slugs to the bottom of the strings would be 2mm or more greater for the neck pickup than the bridge p/u (because the string vibration is greater at the neck position). 

As a starting point, I usually set the bridge at around 3mm and the neck at around 5mm gap and then raise or lower the bridge p/u for optimum sound and finally balance the height of the neck p/u to balance the volume.

If the above is OK then there is probably something slightly wrong with the wiring (BTW, your bridge earth position will be fine).  It is USUALLY a missing or duff earth - but I find it is worth printing the wiring diagram and then following each wire from the diagram, ticking off each connection point at either end of each wire to check there is not a connection point missing or an obvious dry joint.

Oh - and don't worry too much - I've wired dozens of guitars and basses and it's STILL a surprise and joy when it all works as it should first time :D

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Oh - and worth double checking that the black/white join for both of the two pickups is a good one and that the join is insulated.  The black/white join connects the two coils in each pickup and, if the join is poor or is shorting to earth, it will cut out one of the two coils and halve the output. 

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  • 2 weeks later...

I am back :) 

so, after having double checked 2 times that the connections were fine, I decided to go to my luthier to let him inspect the bass. He was puzzled and could not understand what was going on. The connections were perfect and as per the official Di Marzio wirings diagram. So he started assuming the pickups (or the electronics) could be faulty and perhaps it was the case to return them back to the seller.

Just for curiosuty I asked him to change the configuration of the pickups and invert on purpose the phase, and see what would happen.

Guess what? it was indeed a phase problem, even if the connections were correct! therefore, he said the coil within one of the pickups was probably winded not correctly...

I am quite annoyed because I had to spend €30 to do something I could easily do at home myself. Di Marzio should reimburse me for that :D

Edited by Joker
wrong wording
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