help with jaguar modified wiring

[jaskah]

hello

i have a squier vintage modified jaguar. i wanted to add an additional volume pot (in total: one for neck, one for bridge), retain the master tone pot and use the rhythm circuit for a piezo microphone attached to the tremolo plate--one roller pot for volume, one for tone, the switch to turn on/off the piezo signal. also: when the piezo is engaged it shouldn't affect the operation of the other two pickups. this means, it should be possible for me to have all three sources (neck, bridge, piezo) on, if i choose. for now, i still want to retain the strangle switch in the lower control panel.

basically, i'm at a loss how to wire all this up. any help would be greatly appreciated.

[jvin248]

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You'll need to piece together several wiring diagrams.
Jazz bass with two pickups and two volume controls (there are guitars out there like this but easier to find a bass wired this way)
Piezo circuit like an Esquire (btw, you may want an on-board pre-amp to get that to work, look on ebay for small ones I think less than $2)

To fit in the guitar and minimize extra hole drilling, you can get one of those stacked or concentric pots / knobs. Tip is one pickup, ring is the other.

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[jaskah]

thanks for your reply.

i'll have a look at the jazz bass diagram.

i already bought a preamp for the piezo, but in preliminary testing it already sounded pretty good without the preamp, which would require a 9v battery anyways.

i won't need concentric pots as i already have a lower control plate with three knobs + output jack.

[MayTheFuzzBeWithYou]

Hey cool. I just bought a used VM Jaguar (which should hopefully be here somewhen next week) and thought about either having a Lipstick-PU behind the bridge or as you - a piezo!
So: subscribed! And eager to hear sound demoes of yours if you finish your project before I do!

[Embenny]

It is possible to do what you have outlined passively, but know that you are going to hit technical problems with that piezo - they behave totally unlike magnetic guitar pickups.

For example, capacitance bleeds high frequencies off of magnetic pickups in a relatively subtle way. For piezos, it reduces volume and bass. For that reason, a regular tone control won't work, and you'll have to stick to short cables. Longer cables have more intrinsic capacitance. With magnetic pickups, this means a small amount of treble is lost with a long cable - but for a passive piezo, it means a lot of volume and bass is gone. Truly, a small, cheap preamp solves these major issues.

If you insist on making it totally passive, piezos need to see massive input resistance. You'll have to switch the 50k tone pot to a 1meg, and will still need to put something in the vicinity of a 100-300k resistor in series with the hot lead of the piezo before it hits the pots. Put a .0022uf bypass cap as a treble bleed across the volume pot if you don't want to lose all your treble as soon as you roll down, and use a .0022uf tone cap (one tenth the value of a regular tone cap) on the tone pot as well.

These are recommendations from the cigarbox forum, where people tend to try to make cheap/simple instruments and the question of passive piezos has come up before.

It sounds like you're hoping for the piezo to pick up the behind-the-bridge resonance. This could work, but the signal will be very very low compared to the magnetic pickups and it will still be very temperamental when switching cables etc compared to if you used a preamp.

[jaskah]

thanks for your reply and all this information.

i've actually used piezos in a lot of other applications, but more related to field recording. i've never tried wiring up a piezo to a guitar pot, etc, though have used with mixing boards and had no problems there. obviously a much different situation than used in a guitar.

i already have the 1 meg pots for the rhythm control plate. but thanks for your tips about resistors, etc. this won't be a problem, as i've already installed a treble bleed on the main volume control.

i have a piezo pre-amp but have yet to test it. downside for these is that they need to run from a 9v battery. i'm on a tour a bit of the year and have to fly frequently. from my experience, it's not possible to check in baggage with batteries any longer. this would be a hassle to have to remove the 9v each time i had to fly. and for this reason, i wanted to go the passive route.

but regarding picking up the vibrations from the strings behind the bridge, perhaps someone else can chime in here with their experience. it seems to me that a piezo affixed to the tremolo plate would pick up more vibrations from the strings than an actual pickup would, amplifying only the acoustic vibrations from the strings. but maybe i'm wrong. faction guitars sells vibrato-less plates with cutouts for either a lipstick or strat pickup. could this be a better way of amplifying the strings than a piezo?

[jorri]

The drawback may be that it also picks up knocks to the body, or taps to the pickguard, for example. And especially every creak the tremolo makes.
It would pick up more 'normal string' sound than a magentic pickup, yes. That's dependaing on whether you play BTB or expect it to pick up the resonance from picking in the 'normal' position.
It can be hard to find something without getting rid of the tremolo and using one of those plates. Yet i'm sure there are some thin pickups or something made for acoustics? or midi guitars? I expect it also needs to be very high!

[jorri]

I have some cheap piezos, they are like a sticky pad attached to a jack. Maybe try that, and see if you like it, by putting it on the external side. They are just flat discs. The frequency will be ass, but might show how sensitive a piezo can be in picking up EVERYTHING its attached to.

[jaskah]

thanks for your replies.

i actually just ordered a telecaster bridge pickup to install in one of those faction guitar plates. i've already tried working with a piezo taped to the tremolo mounting plate. this worked pretty well, but i had the piezo plugged directly into a mixer, which went to the amp. i'm not sure how well the piezo would work going through the guitar pots, as mentioned in a previous post here.

in any case, i'm going to compare the telecaster bridge pickup to the piezo and see which provides better results. i'll post my findings here later.