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Les Paul With Piezo Wiring Options


feral_smurf

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My next build is going to be a les paul with a piezo pickups in the bridge. I am just asking whether any of the knowledgeable people here will know whether my plan will work.

I'm new to the wiring thing and don't have much knowledge of complex schemes but if i want to wire the piezo in to the main circuit and be able to control the volume can i just replace one of the tone pots with a volume pot for the piezo. With this pot replaced can i then have 2 output signals, one from the piezo and another from the humbuckers (with master tone wired), and then switch between the 2 signals using a toggle switch at the output jack (i.e 2 signals to one after the switch). This will hopefully let me select between piezo + mixed + normal les paul. Also if all the pickups have induvidual volume pots then will i be able to blend the pickups together on the mixed option without the need for a preamp?

Hopefully you can understand my ramblings

Simon

Ps Could i also replace the toggle switch with a blend pot and get a more gradual effect

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You can hook up piezo passively, but it needs a high impedance volume pot(the Graphtech Ghost system recommends a 5Mohm pot with a 330pf treble bleed). Other than that you just treat it like any other pickup(see the manual for specific instructions).

With the preamp it can be on the same volume as the magnetic pickups though.

I'm not sure how well the volume levels will match without the preamp. I assume the piezo will be pretty damned quiet. The Graphtech manual shows the passive piezo hooked up onto the other channel of a stereo jack, making me think that it won't balance well with the magnetics and should be run independently to an external preamp of some sort(like the house PA system).

As for the blend pot, no you couldn't, because the impedance on the piezos is so high. All of the piezo sound would leak off to ground no matter where you had the pot turned, making it into just another volume pot for the magnetic pickups.

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I have a much delayed LP project with some similar ideas. Unfortunately until I do it I can't give specific details of circuits.

Not sure what you are intending to use as the piezo element...a commercial bridge or a DIY buzzer element kind of thing. On mine, I have put in a khaler trem and mounted a piezo element onto the wood underneath it so far.

Also if all the pickups have individual volume pots then will i be able to blend the pickups together on the mixed option without the need for a preamp?

Well...you definitely need a preamp for any piezo...the impedance mis match and loading is too great. My intention is to add a preamp for the element and a volume control on it perhaps with a pull switch to turn it on. I don't expect great acoustic guitar type sounds, but a percussive edge that I can add to the magnetics.

Rather than a switch...you could wire in a stereo jack socket so that with a stereo lead you could get separate outs...or use a standard lead to have both signals go to the one amp...that is my intention...most likely with a switch jack as well to turn off the battery when unplugged. The idea, like I set up with my sustainers is that the guitar will work without a battery or if goes flat albeit without peizo function.

Best to test ideas a bit at a time I guess...see if you can get a decent sound out of the peizo and try and work out how to integrate the systems before making too much of a commitment to modifying the instrument. One good thing about an LP is that you can hang wires and circuits out the back cavity and there is plenty of room in there to fit a battery and circuit when you have it all working to your satisfaction.

Don't know if that helps...but a piezo added to magnetics can sound great even if the piezo alone might not be that good. To get a really great "acoustic" sound, you are likely to need a commercial bridge and preamp system such as a ghost...but then there is the cost and on mine, prohibits the trem option.

pete

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Cheers for the help, my idea is to buy one of these

http://www.stewmac.com/shop/Electronics,_p...s_T-Bridge.html

Considering it claims it is "high output" and comes with the wiring to directly wire it to a jack, i may just get the bridge then wire it up to see if everything works and buy a preamp if it doesn't. I think this may be the best option.

Just to confirm, i could use a toggle switch like this

http://www.stewmac.com/shop/Electronics,_p...e_Switches.html

to switch between signals on a mono jack. It just seems easier to me if you can switch between acoustic - all - electric quickly and blend them together by altering the volumes than having the whole thing separated as then you can't blend them on a guitar

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The Graphtech Ghost system will do everything you want - you need the Acoustiphonic preamp & Quickswitch (3-way mini toggle). Your magnetic pickup hot (the very end of your magnetic signal chain) will solder to a terminal right on the preamp, and the combined mag/piezo output will go to a stereo jack where your magnetic & piezo signals will come out on ring & tip (but I forget which is which). Plug in with a stereo guitar cable and at the other end rout the signals wherever you want them to go (different amps, etc).

I believe it will come with a volume pot for piezo volume, and there's a trim pot on the preamp to adjust your piezo output to match (or not) your magnetic output. Use a Graphtech piezo bridge and there will be very little soldering to do (mostly things just plug right into the preamp board).

I installed this system in an 8-string and I am very happy with it. No need to cobble together various parts, they have everything you've described already packaged up. They are also really good over the phone (but be aware that you're calling to Canada :D ).

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Cheers for all the help guys. To be honest I think I need to build the guitar first without worrying to deeply about electronics but I do now have an idea of what I want to do.

When it comes down to it I will probably try the piezo bridge out passively to see if it works okay. Then get a preamp if it doesn't. It may save myself £50 for something that isn't 100% needed

Simon

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