Can A 3 Knob Jazz Be Converted Into A 4 Knob??

Most jazzes with a four-knob control plate simply move the output jack to the side of the bass and use the hole it formerly occupied for the fourth knob.

 

That is good, but usually the 1/4" jack hole is smaller than the others. The hole will most likely need to be widened. Pretty easy though. Also, Be very careful drilling through the side of the bass. The paint can be fragile and chip. No problem if the chips are small enough to be covered by the output jack plate.

 

Aye, use a very sharp bit, a machine bit would be recomended Id think, and a drill that can be adjusted to a slower speed might be needed as well. Not that I know what Im talking about, it might need a faster drill to avoid chipping, but Id check into things like that maybe on the luthiers section. Im sure those guys could recomend the proper tools for the job.

 

You could always use a stacked knob ?

 

I put an aguilar obp-3 in a jazz with battery using theh standard plate. I used stacked volume knobs, and a stacked bass and treble knob. Everything fit. The only modification I had to make was to route out the hole a little deeper

 

+++1 Stack knobs would be a great solution and you would not have to worry about hoggin out the body for a new input jack

 

There are other options as well. A J-Retro is a very nice drop-in unit which takes very little skill to hookup.The preamp & knobs are already installed on a control plate. Bartolini also offers pre-wired harnesses that will save you time and soldering. Neither of these require any drilling or routing. What if you change your mind & want to return to the original setup? You can't undrill a hole.