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More piezo questions


killemall8
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So i have been revisiting the idea of doing a guitar with a piezo.

I still cant seem to find a diagram of wiring for a 2 humbucker guitar with a 3 way mini switch to swith between piezo, mix of piezo and electric and electric.

Also,

It was said that you need a preamp. Woudl something like this work?
https://www.allparts.com/PU-6413-000-Piezo-Preamp-with-Volume-and-Tone_p_3114.html

With this bridge:

http://www.ebay.com/itm/131316549964?_trksid=p2060778.m1438.l2649&var=430617605945&ssPageName=STRK%3AMEBIDX%3AIT

It looks like it has a 1/8" plug. How do you even wire that to the preamp?

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Here are a couple thoughts:

- I used two blend knobs, one to continuously blend the two magnetic pickups and one to blend the output of the magnetic pickups with the piezo. This allows for a very wide range of sounds and reduces the need to fuss with the preamps trim pot to get just the right level between magnetic and piezo.

- If you must use a switch, you will need something to deal with the two humbuckers before they get to your three way that will then be wired like any other three way.

- For a preamp, I really like the Cafe Walter PZP-1. The design is on his website and it is really simple to make. It took me half an hour several years ago when I had the world's worst soldering iron and hadn't soldered in half a decade. It is simple and works well, though I changed the final trim pot to be wired like an actual volume instead of a variable series resistance so that I could trim its output better (it can provide a surprising amount of gain).

- I wire a stereo output jack such that the battery ground is lifted when there is no cable in place, but this should be an old trick to anyone who has ever used actives.

- For the bridge you show, I would cut off the 1/8" connector and direct solder the leads to the preamp.

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The piezo will need a preamp no matter what. The preamp and bridge you link to should work fine together. The 1/8" plug on the bridge looks like it will mate directly with the socket on the preamp circuit board without having to cut/solder anything. There are probably zillions of similar units out there offered as ready-to-go products or build-it-yourself too.

The problem will be blending piezo and passive pickups, as the impedances the two pickup systems operate at are quite different. As a somewhat-dubious analogy, it's roughly equivalent to hitching up a Honda Civic and a Ford Mustang side by side to the same trailer, opening the throttle on both cars to 50% and expecting the cars to travel in a straight line. Both vehicles can independently pull the trailer fine, but if both are trying to pull simultaneously the Mustang (passive pickup) is obviously going to dominate the pulling power of the two and swamp the Civic (piezo), and the car/trailer combo will drift in the direction the Mustang is leaning.

This means fitting a buffer to the passive pickups and switching/blending after the buffer. Using the above analogy, to equalise the pulling power of the two cars you want the Mustang to be a bit more polite like the Civic, and the Civic to have a bit more oomph to keep up with the 'Stang. The preamps and buffers help achieve this. There appear to be some buffer kits out there expressly designed for interfacing the two systems in one PCB. Another option that may work is to use active pickups and blend them with the preamped-piezo signal, negating the need for the buffer for the passive pickups.

Providing you can find some way of getting the piezo to play ball with the regular pickups, the switch you install to select piezo/piezo+pickup/pickup should be exactly the same as a regular Les Paul three way switch. If your guitar already has a three-way for two humbuckers, you're effectively stacking two of these switches one on top of the other.

Another option is not to blend on the guitar at all and keep the two signals independent - fit two output jacks to the guitar, one for passive and one for piezo. Both signals can then be sent to two separate amps/channels. The piezo/blend/passive switch on the guitar can then operate as a three-way cut switch that turns off the unwanted output.

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  • 2 weeks later...

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