Gain Between Pickups - EB0 (modified)

rvana · « **on:** February 15, 2009, 04:56:39 AM »

I'm finally getting around to reworking a late 1967 EB0 modified to have 2 bridge pickups by some long ago previous owner. Here's the problem: when switching the pickup selector (a three-position switch, from bridge to both to humbucker) the volume drops almost to nothing when picking the humbucker. The humbucker is there and sounding good if you adjust the volume at the amp, but is at a way lower level than the bridge pickups. My assumption is that the gain between the pickups must be vastly different.

Shouldn't there be a capacitor or something in-circuit so that the pickups have relatively the same volume level? It would seem a real pain to have to adjust volume every time you wanted another tonal variation.

I'm neither a guitar tech nor an experienced player on an EB bass, so pardon me if this is a newbie question -

Thanks - Bob

jules · « **Reply #1 on:** February 15, 2009, 02:47:18 PM »

Well the neck humbucker is naturally very hot. How are the heights between each pickup and the strings? The older EBs (pre 1970) didn't have any height adjustment for the neck pickup. There would have been a piece of foam underneath the pickup, pushing it up against the chrome cover, and that's it.

If the new bridge pickup is comparitively high - sitting just under the strings - it may account for the stronger signal. Try lowering them as much as possible.

The electrical resistance of the neck humbucker should be around 30k ohms - you could also check that that is the case.

Do you know what the bridge pickup is?

rvana · « **Reply #2 on:** February 15, 2009, 06:11:22 PM »

There is no name listed anywhere on the bridge pickups. But you may have solved the problem for me inadvertently. I'd never looked at the distance of the pickups from the strings. When I removed one of the bridge pickups to find out who made it, I discovered a foam spacer almost as thick as the pickup itself. The pickups are 1.5cm thick and the spacers are 1.1cm. The bridge pickups are only 0.4cm from the strings while the humbucker is 0.8cm from the strings.

I can certainly play with the rubber shim backing distance on the bridge pickups, which should then reduce their sound.

Is there some "standard" setup distance for pickups from the strings, or is that trial-and-error, or the art of the guitar tech?

Thanks - Bob

anyfour · « **Reply #3 on:** February 16, 2009, 03:23:45 AM »

The height is a matter of taste, really. I like mine close to the pickups to get a hotter signal, some like them farther away for a warmer mellower tone. As long as they are balanced, neither is more right than the other. But be sure you dont put them so close that the strings hit them.

jules · « **Reply #4 on:** February 17, 2009, 01:18:14 AM »

Quote from: rvana

Is there some "standard" setup distance for pickups from the strings, or is that trial-and-error, or the art of the guitar

Well you are limited by the lack of height adjustment in the neck pickup. You want to get it set so that you get an equal volume from both pickups. Raise the neck pup as much as you can, and then lower the bridge until going from one pickup to the other doesn't result in a masive volume change.

This may take a bit of work; you may get it right at home, only to find at gig time it is a bit off - but as long as it is close enough you can leave the fine tuning to your volume controls.

rvana · « **Reply #5 on:** February 18, 2009, 11:11:30 PM »

I split the rubber backing on the two bridge pickups in two and re-bedded them. When I screwed them in, they were roughly at the same distance as the humbucker. Amazingly, the bass, sounds great!

Now I'm going to be forced to play with the distances even more. As Jules suggested, move the humbucker closer, etc. It is a shame there isn't some simpler way to accomplish all this.

I do like that muddy humbucker sound, though. It is almost as though you feel it more than hear it in the low register.

Bob