Chuck’s JB-4 “ Bass IV” build

[Chuck]

Okay, on to the next build! I received a JB-4 kit from the family for my birthday as I’ve been working on a plan based around it for a couple of months. Once the kit arrived I did a quick check of everything and it all looked good. Whereas the “Telemaster” build was focused on the finish and the body reshaping, the plan here is more around a creative process with the wiring. What I’m planning to do is use a similar setup to a Fender Bass VI, but with three jazz pickups. The difference is that, other than just being a 4-stringer, each pickup will have its own “stack” vol/tone control using concentric pots. Each of the three pickups will be able to be switched on and off like the Bass VI, but I won’t be including the “strangle” switch (not really applicable for a standard bass I figure). The third pickup will be located very close to the neck. The lack of a master tone/vol could make it a little fiddly live, but should be fine for home recording and it will hopefully give me some interesting sounds.

The original plan also included a stereo output jack, where the tip could be routed to one amp and the ring to another, and having a three way switch for each pickup so I could send one pickup to one amp and the other pickups to another. I’ve now decided that’s a bit of overkill for a four-string bass, but may well use the idea on a guitar build in the future.

Anyway, other than the wiring I’ll also be doing a bit of re-shaping on the body (‘cos I can’t help myself), and some other component mods – but we’ll see what happens with them as it progresses.

I’ve already ordered all the extra bits I need, so this weekend I’ll hopefully get started.

[Dedman]

Can't wait to see what you come you come with !

[Chuck]

A bit of progress over the weekend… I marked up the body with the reshaping and routing I need to do…


... and then made a routing template for the switch cavity and the third pickup…


Next I attacked the horns to get a more “Bass VI” feel...


And finally broke out the router, and while it’s not the neatest job, it will do (all the messy bits will get covered by the pickguard anyway).


Next steps will be a little bit of work on the bridge pickup cavity. The current hole is designed for the shorter pickup – something a friend also had with his JB-4 kit build – so need to expand the tab slots a little to take the longer pickup. (Might be something to talk to the manufacturers about Adam?)

I might expand the middle pickup cavity a little too as getting the three pickups evenly spaced is very tight at the moment. And of course, sanding, sanding, sanding...

[wazkelly]

Not wrong about bridge PUP rout as it will take a stock Chinese PUP but when I tried to install Entwistle upgrades the 4 lugs for the adjustment screws were spread a little more outwards and this required a bit of reshaping to make things fit, both on the body and with the pick guard for the neck PUP.

If you are thinking about shifting the neck PUP (or middle in this case) the pre cut scratch plate tends to dictate where it should sit and you may need to order a blank so you can custom cut to suit.

DB might be able to add more than me but aren't PUP's supposed to be located somewhere near a naturally occurring harmonic or can you just plonk them anywhere?

[Chuck]

Not wrong about bridge PUP rout as it will take a stock Chinese PUP but when I tried to install Entwistle upgrades the 4 lugs for the adjustment screws were spread a little more outwards and this required a bit of reshaping to make things fit, both on the body and with the pick guard for the neck PUP.

If you are thinking about shifting the neck PUP (or middle in this case) the pre cut scratch plate tends to dictate where it should sit and you may need to order a blank so you can custom cut to suit.

DB might be able to add more than me but aren't PUP's supposed to be located somewhere near a naturally occurring harmonic or can you just plonk them anywhere?

Cheers Waz - I have read about that harmonic thing, but what I've read says it only really applies when playing an open string: the harmonics are constantly shifting every time you fret so it's not quite as important as it may seem. The bridge pickup will be in the normal place, and the "middle" one will only be a mm or two away from it's "normal" position. The third "neck" pickup will be placed at effectively the 24th fret position - from what I understand this is basically where a Rickenbacker 4001 pickup lives, so will hopefully contribute something a little like that kind of sound. Oh, and I already have the pickguard blank ready to roll!

[wazkelly]

Sounds like you have it all sorted and eagerly awaiting how things progress.

[ThreeBbass]

This is going to be great when it's done.
I reckon you could just use a volume pedal to reduce the worry about volume pot gymnastics when you play it.

[Chuck]

This is going to be great when it's done.
I reckon you could just use a volume pedal to reduce the worry about volume pot gymnastics when you play it.

Good thinking - and in a bizarre coincidence just yesterday I was thinking about converting an old busted Vox 847 wah into a volume pedal!

[Chuck]

A very pleasant day of building so far! I ended up taking the jigsaw/rasp/sandpaper to the body a bit more (taking a bit of the upper rear bout and changing the angle of the rear end a bit!), as well as fixing up the cavities. I also shaped the headstock – a freehand version of a Fender one as I like the shape but don’t want to have an “exact” replica.


I then went through the same sanding process I went through last time on the body. I realise most start with 240, but I quite like starting with 60! I realise that the body reshaping I do means more of a heavy-handed sanding approach, but I do find that it’s nice to be able to change the feel of other areas of the body that I haven’t cut – contours, the profile of edges etc. So I basically go 60, 120, 180, 240, 320, wipe body with damp cloth to raise fibres, 400, do a timbermate slurry, let dry, then a final 400 to get it ready for priming. And that’s where I am now: body mounted on trusty painting stick!


With any luck I'll get a couple of primer coats on and hopefully the first of the colour coats before the weekend is done!

[Chuck]

And as hoped, first colour coats went down. Only a key coat and then one more light one over it so far so very patchy, but I think the colour will work well. For those interested I did a three light coats of White Knight general purpose primer, then MTN94 RV-173 Ultraviolet.