Shimming to balance pickup volume? (tall pickups with low action)

[Mobile Sprout]

So I have a fretless jazz bass with DiMarizo model J pickups. I had it set up by a pro when I bought it two years ago. Having played it a lot more since then, I've come to notice that the neck pickup is way louder than the bridge.

I have been wondering, why did the tech not lower the neck pickup to balance the volume? Then I got to thinking - my DiMarzio Model Js are taller than the stock pickups, and I do have very low action... maybe he couldn't lower the pickup any more? I know for certain he did not shim the neck.

I took the bass in today to a second tech along with another bass (note, these are both Talkbass recommended guitar pros) and described the problem, and the guy is immediately telling me he'd probably put a shim in to raise the neck. I hung on to the bass to get a second opinion...

My thoughts are that with such a significant volume difference between the pickups you'd need a large shim to balance them out... and that sounds like a bad idea.

What do you think? Is it a preposterous notion to use a neck shim to manage pickup volumes? Do I just live with the loud neck pickup?? I may take it back to the first tech and see what he thinks. It seems weird that he would just not notice the volume difference...

[ByF]

Have you tried to adjust the pickups to balance the volume?

Usually the neck p'up needs to be lower than the bridge p'up because the strings deflect more closer to the neck. If they are the same height relative to the body, the neck will be louder.

With a screwdriver and about five minutes of your time, you can figure this out for yourself.

Ed

[mongo2]

Originally Posted by Mobile Sprout

Is it a preposterous notion to use a neck shim to manage pickup volumes?

No.

I've used full pocket flat shims to raise the neck for a few reasons: action is preposterously high, there isn't enough breakangle at the saddle, or the pickup adjustment bottoms out. The cause of that may be the neck pocket being cut too deep, the neck heel being too shallow or both. Are you sure the neck pocket isn't too deep? It should be 5/8" deep or thereabouts.

Raising the neck with a flat shim will allow you to raise your strings so you can get more latitude in the pickup height adjustment but won't change the neck/body geometry.

However, as you mentioned the amount of shimming may be prohibitive if the pickup is too tall (even if the neck pocket isn't too deep).

Another approach, though more invasive, would be to deepen the pickup cavity, or a combination of deepening the cavity and using a flat neck shim.

[tom once dead]

I would just screw the neck pup right down, and raise the brige right up.

[Mobile Sprout]

I've never adjusted my pickups before.. I'm worried the pickup is already bottomed out and that'll I'll hurt the screw or something by twisting it past its lowest point. I mean why else would the first guy leave it at the same level as the bridge pickup?

I guess I could take it in and let someone shim the neck.. but I'm worried it won't play the same. Right now the neck is extremely straight and the bass plays better than most other fretlesses I've handled..

[spideyjg]

Push on the pickup and see if it will sink further into the body. If so, tweak the heights of both to suit you.

Many pickups sit on hunks of foam, others on springs but all can be adjusted.

Jim

[ByF]

Originally Posted by Mobile Sprout

I mean why else would the first guy leave it at the same level as the bridge pickup?

Because he was a in a hurry and forgot to adjust he pickups? Because he was lazy, and didn't think you'd notice? Because his boss was hassling him to work faster, and he said "Screw it, this one's done." Because you paid him to adjust the action, but you didn't say anything about adjusting the pickups, so he left them alone?

Don't assume because he's a "pro" that everything he did is sacred and not to be disturbed. He might have just not bothered to check or adjust the pickups. It is quite possible to set up a bass without ever plugging it into an amp, so he probably didn't even notice.

It's your bass, you're entitled to turn the screws. Don't even think about shimming the neck until you find out if you can adjust the pickups.

If you're worried about the screws being bottomed out, loosen them first, and then tighten them. That way you'll know what it feels like when it's not bottomed.

Ed

[mongo2]

Originally Posted by Mobile Sprout

I've never adjusted my pickups before...

You haven't adjusted your pickups yet and you're talking about shimming?

Here's a little secret that might just fix it...I have to whisper it so the others won't hear...ADJUST THE FREAKIN' PICKUPS FIRST!

[JLS]

Originally Posted by mongo2

You haven't adjusted your pickups yet and you're talking about shimming?

Here's a little secret that might just fix it...I have to whisper it so the others won't hear...ADJUST THE FREAKIN' PICKUPS FIRST!

Maybe getting it PLEKKED, will fix that!

[Jo6Pak]

Its is my understanding that it is not uncommon for the Model J pups to bottom out in the cavitiy due to their larger size. What I don't understand is, if the front pup is bottomed out (or very near it), then so should be the rear pup, no? I know you said you had low action, but rather than try to lower the bottomed out front pup, why not try to RAISE the rear one? Might only require adding more foam (if there is any foam at all) to get it jacked up to where you need it in order to even out the volumes. Shimming is still another option, so might be new (different) pups.

[bearshimmy]

you can lower the pole pieces of the neck pup and it should be fine

[Mobile Sprout]

Haha... Ok I think I should collect some more data before posting much more speculation.

My assumption was that given perfect technique on the part of the first guitar tech that set up the bass, he would have naturally raised the bridge pickup as high as possible without string/tonal problems, and then lowered the neck pickup to manage the volume.

Because the neck pickup is still louder than the bridge, logic would have it that the neck pickup must be bottomed out. However, as has been pointed out, I can't assume perfect setup technique.

I'll examine the bass a little more and try to determine if the neck pickup is bottomed out. Also, I've been thinking of switching to a different kind of string anyway... maybe this can be one grand setup project.

As for the polepieces, I've thought of that. The volume change in adjusting those is small compared to raising and lowering the entire pickup. I wrote to DiMarzio directly and they agreed that polepiece adjustment will probably not do: those are really for fine adjustment to balance small string-to-string volume differences.