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Stomp box electronics advice

B

balzac

Aug 25, 2005
99
6
Cairns, Queensland
#1
Hey guys

I'm currently toying with throwing together a stompbox for acoustic duo gigs, and I need some wiring / electronics advice ... I've got a few bits and pieces lying around that I want to reuse, but I'm not sure of the best way of putting it all together.

I'm trying to decide whether to just go super simple and use a piezo transducer straight to a 6mm jack or flash it up a bit by wiring the piezo and an old single coil pick-up from a 60s Japanese bass to a vvt control plate from a squier jazz. FYI, I'm planning to screw half of an old licence plate to the top of the box to act as a vibrating membrane for the mag pup.

So whaddaya reckon? Will that work - to just wire it like a jazz but with a piezo replacing the 2nd pup (i.e. solder the mag pup to one volume pot and the piezo to the other)? What do I do about the bridge ground? Do I need it?

Reading up on these, it seems that just using a piezo gives a pretty terrible bass tone right out of the box, and people have used bass pickups with good results - just not sure whether they'll work in combination and if they'll play nicely with the jazz controls.

Also do I need to worry about shielding the inside of the box? I haven't had the pup wired up for a while, but I remember it being a bit noisy. Would re-potting the pup help reduce noise?

Any advice and input would be gratefully received.

Cheers
G
 
#3
I wouldn't recommend using both at the same time without some active electronics. Piezos in this application can be OK straight to a jack, but it will take some experimentation. There are some pretty decent double bass pickups that are passive. Maybe a piezo element from one of these might be the way to go. I don't think you'll have much joy from a $2 disk without an active buffer.

The license plate thing sounds like a cool idea, but you will have to experiment with the (magnetic) pickup placement. I'd recommend a humbucker TBH. You can by a cheapy on ebay for 5 bucks. Wire it like a P bass, but perhaps go with a larger tone cap so you can really make it sound like a kick drum.
 
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#9
I'd connect the bridge ground to the license plate. You won't be able to solder up to it, so you should use a solder tag at one of the screws that holds it in place. If you go with the single coil pickup, be sure to use shielded cabling. I'd be surprised if it was anything other than pressed mild steel, but make sure a magnet sticks to it.
 
#10
Excellent - thanks!

I've ditched the piezo idea and will pull the pots off the jazz control plate to wire it up like standard P-bass.

Magnets do stick to the licence plate, so that should be all good. Off to the store for some shielded cable now :-)

Any thoughts on the necessity of shielding the box? I have some copper tape and was thinking to line the box with it, but not sure if it'll achieve anything. Probably can't hurt, right?

Thanks guys.
 
#11
I wouldn't bother shielding the whole box. The pot casings will need earthing for shielding. I'd run a strip just where the pots are to avoid soldering up to the casings. And seeing as how you won't see the pickup, I'd just wrap it in copper tape. (Wrap it in masking tape or electrical tape first.) Or if it has a plastic cover, just wrap this in copper tape. Just don't short the coil terminals (if there are any).

Oh, and when you solder the earth wire to the copper tape, just be careful not to linger and risk melting the insulation tape or coil windings underneath.
 

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